Webasto Thermo 90, Thermo 90-TRS, Thermo 90 S, Thermo 90 S-TRS Workshop Manual

Water Heaters

09/2001

Workshop Manual

Thermo 90
Thermo 90-TRS

(Transport of hazardous goods)

Thermo 90 S
Thermo 90 S-TRS

(Transport of hazardous goods)

Type BW 80 (Fuel)
Type DW 80 (Diesel)

Thermo 90 List of Contents

I

List of Contents

1 Introduction

1.1 Scope and Purpose..............................................................................................................

................. 101

1.2 Meaning of Warnings, Cautions, and Notes ......................................................................................

.... 101

1.3 Additional Documentation to be used..........................................................................................

.......... 101

1.4 Safety Information and Regulations.............................................................................................

.......... 101

1.4.1 General Safety Notes........................................................................................................

.......... 101

1.5 Legal Provisions for Installation............................................................................................

................. 102

1.6 Corrections and Improvements................................ ... .... ... ... ... .... ... ... ... ....... ... ... ... .... ... ... ... ... ....

............. 103

2 General Description

2.1 Combustion Air Fan...........................................................................................................

.................... 202

2.2 Heat Exchanger.................................................................................................................

.................... 202

2.3 Temperature Sensor................................ ... ... .... ... ................................................................

................. 203

2.4 Temperature Limiter ...... ... .... ... ... .......................................................................................

.................... 203

2.5 Burner Insert................................................................................................................

.......................... 203

2.6 Glow Plug ....................................................................................................................

.......................... 203

2.7 Flame Sensor .................................................................................................................

....................... 203

2.8 Combustion Tube ..............................................................................................................

.................... 203

2.9 Circulation Pump ...............................................................................................................

.................... 203

2.10 Control Unit..................................................................................................................

.......................... 203

2.11 Dosing Pump........................................... .......................................................................

....................... 203

3 Troubleshooting

3.1 Switch-on.....................................................................................................................

.......................... 301

3.2 Heating Operation..............................................................................................................

.................... 301

3.3 Control Operation ..............................................................................................................

.................... 301

3.4 Switch-off.....................................................................................................................

.......................... 301

3.5 Functions of the Heater in TRS Vehicles.............................. ... .... ... ... ... ... .......................................

....... 301

3.6 Malfunctions.................................................................................................................

.......................... 303

3.6.1 Switch-off upon Failure......................................................................................................

.......... 303

3.6.2 Diagnosis after Switch-off upon Failure (Thermo 90)

.................................................................. 303

3.6.3 Diagnosis after Switch-off upon Failure (Thermo 90

S)............................................................... 303

4 Technical Data..

.............................................................................................................................................. 401

5 Troubleshooting

5.1 General........................................................................................................................

.......................... 501

5.2 General Failure Symptoms............ .... ... ...... ... .......

................................................................................. 501

5.3 Failure Symptoms after Switch-off upon

Failure.................................................................................... 502

5.4 Visual Inspection for Assessment of Burner Condition

.......................................................................... 503

5.4.1 Burner Housing........................... ... ... ... .... .......................................................................

............. 503

5.4.2 Rear Wall with Metal Evaporator... ... ... .... ... ... ... .......................................................................

.... 504

5.4.3 Combustion Chamber...........................................................................................................

....... 504

5.4.4 Burner Assembly........................................ ... ... .... ..........................................................

............. 504

List of Contents Thermo 90

II

6 Functional Tests

6.1 General........................................................................................................................

......................... 601

6.2 Adjustments.....................................................................................................................

..................... 601

6.2.1 Adjustment of the CO

2

Contents ....................... ... ... .... ... ... ... ...................................................... 601

6.3 Components Testing... .... ... ... ... .... .......................................................................................

.................. 601

6.3.1 Temperature Sensor Resistanc

e Check.. ... .... ... ... ... .... ............................................................... 601

6.3.2 Glow Plug Resistance Test.............................

............................................................................ 601

6.3.3 Flame Sensor Resistance Test................................................. ... ... ...... .... ... ... ... .... ... ... ... ... .......

.. 601

6.3.4 Combustion Air Fan Test.......................................................................................................

..... 601

7 Circuit Diagrams

7.1 General........................................................................................................................

......................... 701

8 Servicing

8.1 General........................................................................................................................

......................... 801

8.2 Work on the Heater.............................................................................................................

.................. 801

8.3 Work on the Vehicle............................................................................................................

.................. 801

8.4 Heater Test Run...............................................................................................................

..................... 801

8.5 Servicing......................................................................................................................

......................... 801

8.6 Visual Inspections and Installation Regulations

.................................................................................... 803

8.6.1 Connection to the Vehicle's Cooling System.............................................................................. 803

8.6.2 Connection to the Vehicle's Fuel System..........

......................................................................... 803

8.6.3 Dosing Pump..................................................................................................................

............ 805

8.6.4 Fuel Filter..................................................................................................................

.................. 806

8.6.5 Combustion Air Supply................................................ ... ... ... .............................................

......... 806

8.6.6 Exhaust Line.................. .... ... ... ... .................................................................................

............... 806

8.7 Removal and Installation.

...................................................................................................................... 807

8.7.1 Heater, Removal and Installat

ion................................................................................................ 807

8.7.2 Replacement of Circulation Pump..............................................................................................

807

8.7.3 Replacement of Temperature Limiter

......................................................................................... 807

8.7.4 Replacement of Temperature Sensor...

...................................................................................... 807

8.7.5 Replacement of Combustion Air Fan.................

......................................................................... 807

8.8 First Operation.................................................................................................................

..................... 807

Thermo 90 List of Contents

III

9Repair

9.1 General........................................................................................................................

.......................... 901

9.1.1 Work on Components after Disassembly .................................................................................... 901

9.2 Disassembly and Assembly......................................................................................................

............. 902

9.2.1 Electrical Connections.......................................................................................................

.......... 902

9.2.2 Replacement of Circulation Pump

............................................................................................... 903

9.2.3 Replacement of Temperature Limiter..........................................................................................

904

9.2.4 Replacement of Temperature Sensor ......................................................................................... 90

4

9.2.5 Replacement of Combustion Air Fan...........................................................................................

906

9.2.6 Replacement of Burner, Flame Sensor, and Glow Plug

.............................................................. 907

9.2.7 Replacement of Burner Head..................................................................................................

.... 909

9.2.8 Replacement of Heat Exchanger...................

.............................................................................. 910

10 Packaging/Storage and Shipping

10.1 General.....................................................................................................................

........................... 1001

List of Figures Thermo 90

IV

List of Figures

301 Functional Sequence .................... ............................................................................................................. 302

501 General Failure Symptoms ........................ .... ... ...... ... .... ... ... ... .... ... ... ... .... ... ... ... ... .... ... ...... .. ..

..................... 501

502 Failure Symptoms after Swit

ch-off upon Failure.. ... ... .... ... ... ... ................................................................... 502

503 Visual Inspection, Burner Real

Wall........................................................................................................... 503

504 Visual Inspection, Pilot Flame Exit Bore ....

................................................................................................ 504

505 Visual Inspection, Burner Assembly ..........

................................................................................................ 504

701 Pin Assignment..............................................................................................................

............................. 701

702 Circuit Diagram Automatic Control for

Thermo 90, 12 and 24 V with Triple Timer .................................... 702

703 Circuit Diagram Automatic Cont

rol Thermo 90-TRS, 24 V ........................................................................ 703

704 Circuit Diagram Automatic Control for

Thermo 90 S, 12 and 24 V with Standard Timer........................... 704

705 Circuit Diagram Automatic Control for

Thermo 90 S-TRS, 24 V................................................................ 705

706 Circuit Diagram Automatic Control for

Thermo 90 S-TRS, 24 V without Auxiliary Drive ........................... 706

801 Example for Heater Installation in Lorry

...................................... ... ... ... .... ... ... ............................................ 802

802 Fuel Supply.................................................................................................................

............................... 803

803 Webasto Fuel Tank Tap........................................................................................................

..................... 804

804 Fuel Tapping from Plastic Tank

(tapping via fuel drain plug)...................................... ... ... .... ... ... ... ... . ........ 804

805 Fuel Tapping from Plastic Tank (tapping via fitting plate).................................................................

......... 804

806 Pipe/Hose Connection ............... .......................................................................................

......................... 805

807 Dosing Pump, Installation Location and Att

achment ................................................................................. 805

808 Exhaust Muffler, Direction of Flow ........................................................................................

..................... 806

901 Electrical Connections ......................................................................................................

......................... 902

902 Replacement of Circulation Pump

............................................................................................................. 903

903 Replacement of Temperature Limiter and

Temperature Sensor ............................................................... 905

904 Replacement of Combustion Air Fan.............

............................................................................................ 906

905 Replacement of Burner, Flame Sensor,

and Glow Plug ............................................................................ 908

906 Replacement of Burner Head

.................................................................................................................... 909

Thermo 90 1 Introduction

101

1Introduction

1.1 Scope and Purpose

This repair shop manual is intended to support
familiarised personnel in the repair of Thermo 90 and
Thermo 90 S for the Diesel and fuel type.

The water heater may only be operated with the specified
fue

l (diesel or also fuel oil EL) and the relevant desig nated

type of electrical connection.

1.2 Meaning of Warnings, Cautions,
and Notes

WARNINGS, CAUTIONS, and NOTES in this manual
have the following meaning:

WARNING

This heading is used to highlight that non-compliance
with instructions or procedures may cause injuries or
le

thal accidents to personnel.

CAUTION

This heading is used to highlight that non-compliance
with instructions or procedures may cause damage to
eq

uipment.

NOTE

This heading is used to highlight and draw specific
attent

ion to information.

1.3 Additional Documentation
to be used

This workshop manual contains all information and
procedures necessary for the repair of heaters Thermo 90
and Thermo 90 S.
The use of additional documentation is

normally not
necessary.
Operating instructions/installation instructions and the
ve

hicle specific installation proposal may be used as

complementary information as necessary.

1.4 Safety Information and Regulations

The general safety regulations for the prevention of
accidents and the relevant operating safety instructions
have to be observed at all times.
"General Safety Regulations" beyond the scope of these
re

gulations are detailed in the following.

The specific safety regulations applicable to this manual
ar

e highlighted in the individual chapters by Warnings,

Cautions, and Notes.

1.4.1 General Safety Notes

Within the scope of the StVZO (Road Licensing
Regulations of the Federal Republic of Germany)
"Design General Approvals", laid down by the Federal­Office for Motor Traffic, exist for the Water Heater
Th

ermo 90 with the following official marks of conformity:

~S231 for water heater Thermo 90 and

Thermo 90 S Fuel Type BW 80

~S232 for water heater Thermo 90 and

Thermo 90 S Diesel Type DW 80 and
for water heater Thermo 90-TRS and
Thermo 90 S-TRS Diesel Type DW 80.

The installation of the heaters is to be performed in
accordance

with the installation instructions and must be
checked in case of
a) the vehicle type inspection in accordance with

§ 20 StVZO

b) the individual inspection in accordance with

§ 21 StVZO or

c) the examination in accordance with § 19 StVZO

p

erformed by an officially authorised expert or
examiner for road traffic, a vehicle inspector or a
public servant as per section 7.4a of Annex VIII to
the StVZO.

In the event of c) the installation must be certified
on the acceptance certificate included in the copy of the
"Gene

ral Operating License" giving details about
– manufacturer
– type of vehicle and
– vehicle identification number.
This validates the "Design General Approval". Th

e

acceptance certificate must be kept with the vehicle.

The year of first operation must be permanently
mark

ed on the identification label by removing the

relevant number of the year.

The heaters are cleared for heating the passenger and
driver cabins but not for he

ating compartments used for
the transportation of dangerous goods.
The use of the heater in special vehicles (e.g. vehicles for
the tran

sportation of dangerous goods TRS) or vehicles
not subject to the StVZO (e.g. ships) is partly governed by
regional regulations.

1 Introduction

102

For the installation of the Thermo 90-TRS or
Thermo 90 S-TRS in vehicles used for the transportation
of da

ngerous goods, in addition to the StVZO, the
requirements in TRS 002 and TRS 003 (Technical
Guidelines for the Transportation of Dangerous Goods on
Roads) must be met.

The heater may only be installed in motor vehicles or in
in

dependent heating systems with a minimum coolant

capacity of 6 litres.
The heater must not be installed in the passenger or

driver compartments of vehicles. Should the heater
neverthe

less be installed in such a compartment, the
installation box must be sealed tight against the vehicle
interior. There must be sufficient ventilation of the
installation box from the exterior in order not to exceed a
maximum temperature of 60° C in the installation box.
Excessive temperatures may

cause malfunctions.

WARNING
Due to the danger of poisoning and suffocation, the
hea

ter must not be operated in enclosed areas such
as garages or workshops without an exha ust venting
facility, not even if the start-up is activated by the
timer or telestart device.

At filling stations and fuel depots the heater must be
swit

ched off as there is a potential danger of

explosion.

CAUTION
Where flammable fumes or dust may build up
(e

.g. in the vicinity of fuel, coal, wood, cereal depots,

o

r similar installations) the heater must be switched

off to prevent explosions.

In the vicinity of the water heater a temperature of 85° C
m

ust not be exceeded under any circumstances
(e.g. during body paint work).
A violation of this temperature limit may cause permanent
da

mage to the electronics.

When checking the cooling water level, proceed in
accordan

ce with the vehicle manufacturer's instructions.
The water in the heating circuit of the heater must contain
a minimum of 10% of a quality brand anti-freeze.

Ignoring the installation instructions and its procedures
wil

l void the warranty granted by Webasto. The same

applies fo

r repairs performed by unskilled personnel and
repairs without using original spare parts. This will void the
water heater's "Official Marks of Conformity" and thus the
vehicle's permit of operation.

1.5 Legal Provisions for Installation

For testing the heater in accordance with § 19, 20, or 21
of the StVZO the following regulations are to be observed
in particular (§ 22 a StVZO):

Testing is performed upon presentation of the operating
a

nd installation instructions of the manufacturer. The
year of the initial operation must be durably marked on
the heater identification plate by the installing person.

Extracting combustion air from the

vehicle interior is not

permissible.
The exhaust line outlet is to be positioned at the top, at

the side, or in case of exhaust venting, below the vehicle
floor, to the ne

arest possible location of the vehicle's or
cockpit side or rear end. Exhaust pipes must be routed
so that exhaust fumes are unlikely to penetrate into the
vehicle's inter

ior. The function of any parts vital for
vehicle operation must not be impaired. Condensation
accumu

lation in the exhaust line must be directly
drained. A condensation drain hole may be provided as
re

quired.

In installations the openings of the combustion air inlet
an

d the exhaust outlet must not allow a ball of 16 mm in

d

iameter to be inserted.

Electrical lines, switch gear, and control gear of the
h

eater must be located in the vehicle so that their proper

fun

ction cannot be impaired under normal operating

conditions.
For the routing of fuel lines and the installation of

add

itional fuel tanks, §§ 45 and 46 of the StVZO are to be

adhered to. The most important regulations are:

• Fuel lines are to be designed in such a way that

they remain unaffected by torsional stresses in the
veh

icle, engine movement, and the like. They must be
protected against mechanical damage. Fuel-carrying
parts are to be protected against excessive heat and
are to be arranged so that any dripping or evaporating
fuel can neither accumulate nor be ignited by hot
components or electrical equipment.

• In busses, fuel lines and fuel tanks must not be located
in

the passenger area or in the driver's compartment.
In these type of vehicles the fuel tanks must be located
such that they do not pose a direct hazard to the exits
in the event of a fire. Fuel supply must not be by
means of gravity or pressurisation of the fuel tank.

Thermo 90 1 Introduction

103

• Installation Instructions for Webasto fuel tanks for the
fuel supply of water heaters in vehicles:
In busses the installation is not permit

ted in the

passengers or driver's compartment.

• The fuel filler neck must not be located in the
passen

gers or driver's compartment of any vehicle.

• Fuel containers for carburettor fuel must not be
located imme

diately behind the front panelling of the
vehicle. They must be separate from the engine so
that even in case of an accident the inflammation of
fuel is unlikely to be expected. This does not apply
for towing vehicles with an open cockpit.

All fuel containers offered in the Webasto
Accessories Catalogue are suitable for a maximum
o

perating pressure of 0.15 bar overpressure.

All fuel containers offered in the Webasto
Accessories Catalogue are subjected during
ma

nufacture to individual pressure testing with at least

0.3 bar overpressure.

• The fuel containers must either be equipped with a
ven

t cap or be ventilated in another way (ventilation

line).
Only filler caps in accordance with DIN 73400 may be

us

ed.

• The operational state of the heater, i.e. an indication
"on

" or "off", must be easily and clearly visible.

1.6 Corrections and Improvements

Deficiencies, improvements, or proposals for correction of
this workshop manual are to be mailed to:

Webasto Thermosysteme International GmbH
Abt. Technische Dokumentation
D-82131 Stockdorf
Telefon: 0 89 / 8 57 94 - 5 42
Telefax: 0 89 / 8 57 94 - 7 57

1 Introduction

104

Page free for notes

Thermo 90 2 General Description

201

2 General Description

The water heater Webasto Thermo 90 and Thermo 90 S
in combination with the vehicle's own heating system is
used to:

– heat the cabin
– defrost the windshields
– preheat water-cooled engines.

The water heater operates independent from the vehicle
en

gine and is connected to the cooling system, the fuel

system, and the electrical system of the vehicle.
The heater, designed to the evaporator principle,

op

erates intermittently and is controlled by the

temperature sensor.
Dependent on the deviation of the current coolant

temp

erature from the rated value of the temperature
sensor, combustion performance is continuously
controlled within the range from 1.8 to 7.6 kW for Diesel
operated heaters and within 2.0 to 7.6 kW for fuel
operated water heaters. For an extremely high heating
performance requirement (preheating) the maximum
performance of 9.1 kW is available in case of Diesel
operated water heaters for up to 2 hours after equ ipme nt
activation.

The water heater Thermo 90 and Thermo 90 S basically
consists of:

– combustion air fan
– heat exchange
– burner insert with combustion tube
– circulation pump

For control and monitoring a
– control unit (external)

– flame sensor
– glow plug
– temperature sensor
– temperature limiter

are located inside the unit.
On the Thermo 90 S heater the control unit may also be

flang

ed to the combustion air fan.

Fuel supply is provided externally by a fuel dosing pump.

Heater Thermo 90

Thermo 90

1 Combustion Air Fan
2 Fuel Connection
3 Temperature Sensor
4 Temperature Limiter
5 Heat Exchanger
6 Inlet, Coolant
7 Circulation Pump
8 Outlet, Coolant
9 Outlet, Exhaust

10 Inlet, Combustion Air

1

2

3

4

5

6

7

8

9

10

NOTE

One of the newer models shown. Older
models have the cable of the temperature
sensor located on the side.

2 General Description Thermo 90

202

Heater Thermo 90 S

2.1 Combustion Air Fan

The combustion air fan delivers the air required for
combustion from the combustion air inlet to the burner
insert.

2.2 Heat Exchanger

The heat exchanger dissipates the heat provided by
combustion to the coolant circuit.

Heat Exchanger

Thermo 90 S

1

2

3

4

5

6

7

8

9

10

11

1 Combustion Air Fan
2 Fuel Connection
3 Temperature Sensor
4 Temperature Limiter
5 Heat Exchanger
6 Inlet, Coolan t
7 Circulation Pump
8 Outlet, Coolant

9 Outlet, Exhaust
10 Inlet, Combustion Air
11 Control unit (may also

be located externally
in the vehicle)

Temperature Limiter

Temperature Sensor

Thermo 90 2 General Description

203

2.3 Temperature Sensor

The temperature sensor senses the coolant temperature
in the heat exchanger of the heater unit as electrical
resistance. This signal is fed to the control unit for
processing.

2.4 Temperature Limiter

The overheat protection (bimetal) protects the heater unit
from excessive operating temperatures. The overheat
protection responds at a coolant temperature higher than
105° C to switch off the heater.

2.5 Burner Insert

Within the burner insert fuel is distributed in the
combustion tube across the burner cross-section.

2.6 Glow Plug

The glow plug ignites the fuel/air mixture at the start of
heater operation. The glow plug is acting as an electrical
resistor and is located in the burner insert opposite to the
flame source.

2.7 Flame Sensor

The flame sensor is a low-Ohm PTC resistor, changing
its resistance dependent on its heating by the flame.
Th

e signals are routed to the control unit for processing.
The flame sensor monitors the flame operating condition
ove

r the complete duration of heater operation.

2.8 Combustion Tube

Inside the combustion tube the combustion of the fuel/air
mixture takes place, heating up the heat exchanger.

2.9 Circulation Pump

The circulation pump provides for circulation of the
coolant in the vehicle and heater circuits. The control unit
switches the pump on for operation throughout the enti re
time of heater operation (also in control idle).

Circulation Pump

2.10 Control Unit

The control unit is the central controlling device for
functional sequencing and monitoring of the combustion
operation. It is located externally in the vehicle, but may
also be flanged to the combustion air fan on Thermo 9 0 S
heaters.

2.11 Dosing Pump

Fuel supply to the heater and its dosing is ensured
externally by a dosing pump. When the heater is
deactivated, it also serves as a shut-off facility.
The magnetic coil of the dosing pump receives the pulses
fro

m the microprocessor of the control unit.

Burner Insert

Glow Plug

Flame Sensor

2 General Description Thermo 90

204

Page free for notes

Thermo 90 3 Functional Description

301

3 Functional Description

(Fig. 301)

3.1 Switch-on

When operating the push button "Immediate Heating",
the "Operating Indicator" on the

timer illuminates
or
by activation with the switch, the operating indicator

integrated in the

switch illuminates.

Circulation pump, glow plug, and combustion air fan are
pu

t into operation.

3.2 Heating Operation

After approx. 50 seconds, combustion commences with
the automatically controlled heating operation in full load
for a maximum of 2 hours.

The vehicle's own heating blower s

tarts to operate only
after the heat carrier (coolant) has accumulated enough
heat. After reaching the pre-coded rated temperature
(see table Control Temperatures) heating performance
precision

control will take over in stages down to the

lowest part load operation.

3.3 Control Operation

If the coolant temperature rises up to the control idle
threshold, the heater enters the control idle phase.
The circulation pump, the vehicle's own blower, and the
op

erating indicator remain in operation during the control
idle period.
After the coolant has cooled down to the precoded
r

eactivation temperature, the heater resumes operation.

Diesel Operated Water heaters

If the water heater'

s water temperature is above the
rated temperature but has not yet reached the threshold
for

control idle with the temperature dropping within
10 minutes back to rated temperature (after reaching it for
the

first time), the water heater reverts to the 9.1 kW
heating stage. Should the rated temperature be obtained
after 10 minutes, there will be an automatic reactivation
only up to heating stage 7.6 kW.

Fuel Operated Water Heaters

The maximum heating performance of fuel operated
water

heaters is always 7.6 kW.

3 Functional Description Thermo 90

302

3.4 Switch-off

When switching the heater off, the operation indicator
on the timer/switch extinguishes. Com

bustion ends and
run-down is initiated. Circulation pump and combu stion air
fan, however, continue operation to cool down the heater
(run-down) and are automatically deactivated after about
90 seconds. A reactivation of the heater during run-down
is permitted.

Room temperature control by me

ans of the vehicle's own
heating blower may be provided in addition to employing
a room thermostat.

3.5 Functions of the Heater in TRS

Vehicles

The heater is started using the switch. A TRS condition
(forced deactivation) will be released after

– the vehicle engine is turned off
– a conveyor facility is started

with the short run-down termi

nating after 20 seconds.

Then the control unit is in the "error lockout" mode. Prior
t

o reactivation the On/Off switch must be set to "Off".

The isolation switch (emergency off switch) must only be
ope

rated in case of emergency, as the heater is switched

off without run-down (overheating possible).

Fig. 301 Functional Sequence

Functional Sequence for Thermo 90

Switch-on
Configuration Check
Preheating 40 sec. (cycled)
Dosing Pump Priming 5 - 7 sec. (1)
Dosing Pump / Part Load (1/4)
Flame Sensor Take-over
Stabilisation Time
Full Load
Vehicle Blower »On«
Control Range
Control Idle
Flame Sensor »cold« (0)
Run-down completed
Preheating 15 – 20 sec. (cycled)

Dosing Pump Priming 5 – 7 sec. (1)
Dosing Pump / Part Load (1/4)
Flame Sensor Take-over
Stabilisation Time
Coolant Temperature down
Full Load
Switch-off (run-down)
Flame Sensor "cold" (0)
Run-down completed

A Glow Plug
B Dosing Pump
C Com

bustion Air Fan

D F

lame Sensor

E Oper

ation Indicator Light

F Circulation Pump

A
B

C

D
E
F
G

1
0
1

0

0

0

0

0

0

1

1

1

1

1

1

/4

1

/2

1

/4

*

30 80 90 75 70 °C

2

3

22

212019171614131110

181512

986431

2 5 7

Sicherheitszeit

❏

* In case of a no-flame-

condition automatic restart
is initiated (20 sec. cycled
preheating, 90 sec. safety
time)

o Possible codeable control

temperatures, see table
below

1
2
3
4
5
6
7
8

9
10
11
12
13
14

15
16
17
18
19
20
21
22
23

Thermo 90 3 Functional Description

303

G Vehicle Blower
Setting of Control Temperatures Thermo 90

On the standard wiring harness B6 is not in use.

NOTE

The selected control idle temperature of the heater
should be below the opening temperature of the cooler
the

rmostat!

Setting of Control Temperatures Thermo 90 S

Connection of signal "motor on"/ "m

otor off" (terminal D+)
to the control unit (connector X12, contact 7) will enable
different thereshold values.

If the signal terminal D+ is not conn

ected, temperatures

will be those linke for "motor off".

NOTE

The selected control idle temperature of the heater
should be below the opening temperature of the cooler
the

rmostat!

3.6 Malfunctions

3.6.1 Switch-off upon Failure

In case of a no-flame condition fuel is delivered for a
max. of 180 seconds.

In the event of a flame-out during operation fuel is
de

livered for a max. of 90 seconds.

Should an overheat condition exist

(after response of the

temperature limiter), no fuel will be delivered.
After switch-off by low voltage protection

for more than 20 seconds there

will be no fuel supply.

After removal of the fault there will be an

error lock-out.

Reset by switch-off and reactivation of the heater.

In case of overheating, the knob of the temperature limiter
ha

s to be reset after the unit has cooled down.

CAUTION

To avoid damage to the component, do not attempt to
re

set the temperature limiter by force while hot.

3.6.2 Diagnosis after Switch-off upon Failure
(Thermo 90)

When operated with switch or triple timer the type of error
lock-out condition is indicated by an operation indicator
light flash code while the heater is in run-down.

After five short signals the following long flash pulses are
coun

ted:

1x No start (after 2 start attempts)
2x Flame-out during operation (repeated > 5)
3x Voltag e to o low
4x Premature flame detection
5x Flame sensor open or short circuit
6x Temperature sensor open or short circuit
7x Dosing pump open or short circuit
8x Fan motor open or short circuit or wrong speed of

fan motor

9x Glow plug open or short circuit

Table

Rated Temp.

at Sensor

Control

Idle

Reactivation

af

ter

Control Idle

Minus to B6
B6 not used
Plus to B6

80° C
72° C
65° C

90° C
82° C
75° C

75° C
67° C
60° C

Table

Rated Temp.

at Se

nsor

Control

Idle

Reactivation

af

ter

Control Idle

"Motor on"
"Motor off"

72° C
80° C

82° C
90° C

67° C
75° C

Thermo 90 Thermo 90 S
12 Volt 10.5 V ± 0.5 V 10.5 V – 0.5 V
24 Volt 21 V ± 1 V 21 V – 1 V

3 Functional Description Thermo 90

304

3.6.3 Diagnosis after Switch-off upon Failure
(Thermo 90 S)

When equipped with a standard timer an error will cause
an output to the timer display:

F 01 No start (after 2 start attempts)
F 02 Flame-out during operation (repeated > 5)
F 03 Voltage too low or too high
F 04 Premature flame detection
F 05 Flame sensor open or short circuit
F 06 Temperature sensor open or sho rt cir cuit
F 07 Dosing pump open or short circuit
F 08 Fan motor open or short circuit or wrong speed

of fan mo

tor
F 09 Glow plug open or short circuit
F10 Overheating
F 11 Circulation pump open or short circuit

When operated with switch the type of error lock-out
co

ndition is indicated by an operation indicator light flash

code while the heater is in run-down.
After five short signals the following long flash pulses are

co

unted:

1x No start (after 2 start attempts)
2x Flame-out during operation (repeated > 5)
3x Voltage too low or too high
4x Pre m at ur e flam e det ec tio n
5x Flame sensor open or short circuit
6x Temperature sensor open or short circuit
7x Dosing pump open or short circuit
8x Fan motor open or short circuit or wrong speed of

fan motor
9x Glow plug open or short circuit
10x Overheating
11x Circulation pump open or short circuit

Thermo 90 3 Functional Description

305

Page free for notes

Thermo 90 4 Technical Data

401

4 Technical Data

As long as no threshold values are given, the following
technical data are understood to include tolerances of
±10% usual for heaters at an ambient temperature of
+20° C and at nominal voltage and conditions.

Electrical Components:

Control unit, combustion air fan motor and dosing pump,
g

low plug, control switch and timer are either of the 12 V
or 24 V type.
The components temperature limiter, temperature sensor,
a

nd flame sensor are identical in the 12 V and 24 V units.
* not for Thermo 90-TRS

1)

Thermo 90-TRS 24 Volts only

2)

Thermo 90-S with control unit mounted on heater

Water Heater Operation Thermo 90 Fuel Thermo 90 Diesel

Thermo 90-TRS

Type BW 80 DW 80
Mark of conformity ~ S231 ~ S232
Heater type Water heater with

Ferro-Tec-Technology

Heat flow max.

control range 2.0 – 7.6 kW

9.1 kW

1

.8 – 7.6 kW
Type of fuel Benzin Diesel
Fuel consumption max.

control range 0.25 – 1.0 l/h

1.1 l/h

0.19 – 0.9 l/h

Nominal voltage 12 Volt 12 or 24 Volt

1)

Operating voltage range 10 ... 15 Volt 10 ... 15 or 20 ... 30 Volt
Rated power consumption with

circulation pump (without vehicle blower)

max.
control range 37 W – 83 W

90 W

3

7 W – 83 W

Permitted ambient temperature:
Heater – operation

– storage

Control unit – operation

– storage

Dosing pump – operation

– storage

–40 ... +110° C
–40 ... +130° C

–40 ... + 75° C
–40 ... + 85° C

–40 ... +20° C –40 ... +40° C

–40 ... + 85° C
Permitted overpressure (heat exchanger) max. 2.0 bar
Heat exchanger capacity 0.15 l
Max. combustion air intake temperature +40° C
Coolant circuit minimum capacity 6.00 l
Volume flow of circulation pump

against 0.15 bar

1650 l/h

CO

2

in exhaust

(perm. operating range)

max. 10 ... 12.0 Vol.-%

CO

2

-setting values at approx. +20° C and

geograph. height above SL

max.

0 m 500 m 1000 m
10 % 10.6 % 11.3 %

Dimensions heater
(Tolerance ± 3 mm)

Length 310 mm (355 mm)

2)

Width 133 mm
Height 220 mm

Weight 4.8 kg

4 Technical Data Thermo 90

402

Page free for notes

Thermo 90 5 Troubleshooting

501

5 Troubleshooting

5.1 General

This section describes troubleshooting procedures for the
Water Heater Thermo 90 and Thermo 90 S.

CAUTION

Troubleshooting requires profound knowledge about
str

ucture and theory of operation of heater components

and may only be performed by skilled personnel.
In cases of doubt refer to Sections 2 or 3 for functional

inte

rrelations.

CAUTION

Troubleshooting is normally limited to the isolation of
de

fective components.
The following defects are not included in the trouble
shoo

ting procedures. Before troubleshooting, check for

and eliminate these defects:

• corrosion on connector

• loose contact on connector

• wrong crimping on connector

• corrosion on electrical wiring and fuses

• corrosion on battery terminals

After any correction of a failure a functional test has to be
pe

rformed in the vehicle; before switch the heater off and
on again.

5.2 General Failure Symptoms

The following table (Fig. 501) lists possible, general failure
symptoms.

Fig. 501 General Failure Symptoms

NOTE

In many cases the probable cause of failure may be the
bur

ner. Perform a visual inspection according to 5.4.

Failure Symptom Failure Symptom Remedy

Heater switches
off automatically

No combustion after start or repeat
st

art

Control unit goes to error lock-out.
Switch heater off and on again

Flame extinguishes during operation If a no-heating condition persists

con

tact Webasto service agent

Heater overheats due to lack/loss of
cool

ant

Replenish coolant.
After cool-down of unit, push button of
temp

erature limiter before reactivation

or replace temperature limiter

Low voltage condition for more than
20 seconds

Check fuses, connections, and charge
of ba

ttery.

Switch-off caused by temperature
limiter

After cool-down of unit, push button
of temperature limiter before
r

eactivation or replace temperature

limiter.

5 Troubleshooting Thermo 90

502

5.3 Failure Symptoms after Switch-off
upon Failure

NOTE

When operated with a switch the type of failure is
ind

icated by a flash code of the operation indicator light

during heater run-down.
After five short signals the long flash pulses are counted.

The heater Thermo 90 S with standard timer outputs
errors to

the timer display for indication (see 3.6.3).
The following table may also be used as representative
re

ference.

Fig. 502 Failure Symptoms after Switch-off upon Failure (Sheet 1 of 2)

Failure Symptom Failure Symptom Remedy

No function Electrical wiring,

fuses

Check fuses
Check battery connections
+ at A5 / – at A3 / + from A1
(Thermo 90)
+ at 12 / – at 9 / + at 3, connector X12
(T

hermo 90 S)

Control unit defective Replace control unit

1 Flash pulse

(no start)

Fuel system Check fuel level

Check fuel filter
Bleed fuel system

Combustion air/exhaust duct Check combustion air/exhaust duct for

f

oreign matter and clean as required

Burner Clean burner or replace as necessary

2 Flash pulses

(flame-out during operation)

Fuel supply Check fuel level

Check fuel filter
Bleed fuel system

Burner Clean burner or replace as necessary

3 Flash pulses

(low voltage)

Electrical power supply Check battery

Check electrical connections

4 Flash pulses

(flame sensor continuously
hot)

Flame sensor defective Replace flame sensor

5 Flash pulses

(flame sensor defective)

Wiring Check wiring for damage,

open connections or short circuit

Flame sensor defective Replace flame sensor

6 Flash pulses

(temperature sensor defective)

Wiring Check wiring for damage,

open connections or short circuit

Temperature sensor Replace temperature sensor

7 Flash pulses (dosing pump

d

efective / overheat protection

defective)

Coolant circuit Check coolant level

Bleed coolant circuit
Reset temperature limiter

Wiring Check wiring for damage,

open connections or short circuit

Dosing pump defective Rep lace dosing pump

Thermo 90 5 Troubleshooting

503

Fig. 502 Failure Symptoms after Switch-off upon Failure (Sheet 2 of 2)

5.4 Visual Inspection for Assessment
of Burner Condition

Burner and evaporator have specific features indicating
their need for replacement or their serviceable condition.
The following describes the criteria

for a correct

inspection.

5.4.1 Burner Housing

• The starting air bore (Fig. 502) must not be clogged,
otherwise there will be no start.

Remedy

Carefully remove any contamination (e.g. with a wire
o

f 1.5 mm diameter). Remove glow plug first.

Fig. 503 Visual Inspection, Burner Real Wall

Failure Symptom Failure Symptom Remedy

8 Flash pulses

(combustion air fan defective)

Wiring Check wiring for damage,

open connections or short circuit

Combustion air fan defective Replace combustion air fan

9 Flash pulses

(glow plug defective)

Wiring Check wiring for damage,

open connections or short circuit

Glow plug defective Replace glow plug

1 Combustion Tube
2 O-Ring
3 Flame Sensor
4 Insulation
5 Glow Plug
6Housing
7Screw
8 Bracket
9 Starting Air Bore

1

2

3

4

5

6

7

8

9

5 Troubleshooting Thermo 90

504

5.4.2 Rear Wall with Metal Evaporator

• The pilot flame exit bore (Fig. 504) must not be
clogged, otherwise there will be no start.

Remedy

Replace burner

• Cracks, delaminations, as well as black or other
dis

colorations of the evaporator do not cause a burner

failure and are meaningless.

• Coke deposits on the evaporator surface (except
for the pilot flame exit bore) are usual and must not be
r

emoved. When the load changes from full load
to part load and vice versa the burner normally is
self-cleaning.

Fig. 504 Visual Inspection, Pilot Flame Exit Bore

5.4.3 Combustion Chamber

• The combustion chamber (Fig. 505) should not be
damaged (e.g. dented).
A combustion chamber with dents may cause
in

sufficient combustion or coking of the heater.

Remedy

Replace burner

• The air bores (Fig. 505) in the combustion chamber
mu

st not be coked. Coked air bores may cause a

no-start or insuffici

ent combustion.

Remedy

Removal of coke deposit

s by careful scraping.

5.4.4 Burner Assembly

• The cables of glow plug and flame sensor must be
routed as shown in Fig. 503.

• The screwed connection of th e ho us ing an d
com

bustion chamber must be secure (Fig. 505).

• Housing and combustion chamber (Fig. 505) must be
con

nected securely without any play (check by slight

movement of fuel pipe).

• The O-ring must have a tight fit around the fuel
cha

mber upper edge (Fig. 503) and must seal

completely.

• The gap between housing edge and combustion
cha

mber upper edge (Fig. 505) must not be equal

around the entire circumference.

• The insulation (Fig. 503) must be present.

Fig. 505 Visual Inspection, Burner Assembly

Pilot Flame Exit Bore

Metal Evaporator, Fuel

Pilot Flame Exit Bore

Metal Evaporator, Diesel

Combustion

Swirl Ring

Air Bores

Gap between Housing and
Combustion Chamber

Chamber

Thermo 90 6 Functional Tests

601

6 Functional Tests

6.1 General

This section describes the on-vehicle and off-vehicle
testing of the heater to check its proper operation.

WARNING

The heater shall not be operated in enclosed areas like
ga

rages or workshops not provided with exhaust venting

facilities.

6.2 Adjustments

6.2.1 Adjustment of the CO2 Contents

A change of the combustion air volume set by the
manufacturer may be performed by rotating the air set
screw.

Setting Procedure

Clockwise rotation: CO

2

value decreases (prior to
measurement; heater must have been in operation for at
least 5 min).
Coarse setting: Rotate air

set screw clockwise fully in

and then back one turn.

6.3 Components Testing

6.3.1 Temperature Sensor Resistance Check

During electrical testing of the temperature sensor using
a digital multimeter, the followin

g readings should be

obtained:
Resistance at 25° C: 990 ... 1010 Ω

Test current: < 1 mA

6.3.2 Glow Plug Resistance Test

During electrical testing of the glow plug using a digital
multimeter, the following readings should be obtained:

Glow plug: 12 Volt (red) 24 Volt (green)
Resistance at 25° C: 0.3 ... 0.6 Ω 1.3

... 1.44 Ω

Test current: < 5 mA < 5 mA

6.3.3 Flame Sensor Resistance Test

During electrical testing of the flame sensor using a digital
multimeter, the following readings should be obtained:

Cold test:

Resistance at 25° C: 2.6 ... 3.4 Ω
Test current: < 5 mA

Hot test:

Resistance at 800 – 1000° C: 12 ... 15 Ω
(ceramic rod red hot over a length of approx. 20 mm)
Test current: < 5 mA

6.3.4 Combustion Air Fan Test

The motor speed check must be performed with the
heater assembled and within the operating voltage range.
During the test check for grinding noises.

NOTE

For the motor speed check the fan cover must be
r

emoved. Prior to re-installation the gasket is to be

renewed.

CAUTION

Pay attention not to break off the lo

cking cams, otherwise

renew cover and gasket.
Speed in control range min. 1800 min

-1

(± 9%)

Speed in control range max. 6100 min

-1

(± 9%)

In case speed values are out of tolerance replace
comb

ustion air fan (see 9.2.5).

NOTE

On the Thermo 90 the function of the combustion air fan
can be

checked with the diagnostic computer or the
components tester.
On the Thermo 90 S the check is performed by means of
the PC heater d

iagnosis.

6 Functional Tests Thermo 90

602

Page free for notes

Thermo 90 7 Circuit Diagrams

701

7 Circuit Diagrams

7.1 General

The circuit diagrams (Figs. 702 and 703) show possible
circuits of the heater Thermo 90 with

– 3-times-clock
– TRS equipment

The circuit diagrams (Figs. 704 through 706) show
po

ssible circuits of the heater Thermo 90 S with

– standard timer
– TRS equipment
– TRS equipment without aux

iliary drive

Fig. 701 shows the pin assignment (X1) for Thermo 90
an

d Thermo 90 S.

CAUTION

The –poles must not be looped or reversed as some
co

mponents are controlled by negative polarity.

Fig. 701 Pin Assignment

789101112

654321

1 = Glow Plug +
2 = Temperature Limiter +
3 = Flame Sensor +
4 = Temperature Sensor +
5 = Circulation Pump +
6 = Combustion Air Fan +
7 = Combustion Air Fan –
8 = Circulation Pump –

9 = Temperature Sensor –
10 = Flame Sensor –
11 = Temperature Limiter –
12 = Glow Plug –

View from rear

7 Circuit Diagrams Thermo 90

702

Fig. 702 Circuit Diagram Automatic Control for Thermo 90, 12 and 24 V with Triple Timer

ϑϑ

bl
br
ge
gn
gr
or
rt
sw
vi
ws

Wire colors

blue
brown
yellow
green
gray
orange
red
black
violet
white

Wire gauges

< 7.5 m 7.5 - 15 m

0.75 mm

2

1.0 mm

2

1.5 mm

2

2.5 mm

2

4.0 mm

2

1.5 mm

2

1.5 mm

2

2.5 mm

2

4.0 mm

2

6.0 mm

2

For fuel heaters remove this connection
Temperature coding (temperature at water outlet):

see table page 302
Timer P:

with plus at connection 4 = permanent operation in immediate heating
without plus at connection 4 = heating period 1 hour

1
2

3

Item Nomenclature Remark

A1 Heater Thermo 90
A2 Control Unit SG 1569
B1 Flame Sensor
B2 Temperature Sensor
B3 Temperature Limiter
B4 Room Thermostat
E Glow Plug
F1 Fuse 20 A Flat Fuse SAE J 1284
F2 Fuse 5 A Flat Fuse SAE J 1284
F3 Fuse 20 A Flat Fuse SAE J 1284
H1 Symbol for “Heating” in Display Operation indication (in item P)
H3 Light Symbol illumination (in item P)
H4 LED max. 20 mA Flame indication ( option)
K1 Relay (in item A2) Master relay
K2 Relay (in item A2) for circulation pump
K5 Relay for vehicle blower
K6 Relay only required for battery switch

in minus

Item Nomenclature Remark

M1 Motor Combustion air fan
M2 Motor Circulation pump
M3 Motor Vehicle blower
P1 Test Unit for diagnosis
P Timer 1529 for pre-timed operation
R Resistor Resistor for H4
S1 Switch for Circulation Pump for separate switch-on
S2 Switch Battery switch in plus
S3 Switch Battery switch in minus
V106 Transistor in item A2
V107 Transistor in item A2
V108 Transistor in item A2
X1 Connection 12-pole on item A1
X2 Connection 8-pole on item P
X4 Connection 2-pole
Y Dosing Pump

Thermo 90 7 Circuit Diagrams

703

Fig. 703 Circuit Diagram Automatic Control Thermo 90-TRS, 24 V

ϑϑ

For fuel heaters remove this connection
Temperature coding (temperature at water outlet):

see table page 302
Switch S6 must be installed so that plus or minus potential is appl ied to the

relevant control inputs of the control unit when a conveyor facility is put i nto
operation.

1

2

3

bl
br
ge
gn
gr
or
rt
sw
vi
ws

Wire colors

blue
brown
yellow
green
gray
orange
red
black
violet
white

Wire gauges

< 7.5 m 7.5 - 15 m

0.75 mm

2

1.0 mm

2

1.5 mm

2

2.5 mm

2

4.0 mm

2

1.5 mm

2

1.5 mm

2

2.5 mm

2

4.0 mm

2

6.0 mm

2

Item Nomenclature Remark

A1 Heater Thermo 90
A2 Control Unit SG 1569
B1 Flame Sensor
B2 Temperature Sensor
B3 Temperature Limiter
B4 Room Thermostat
E Glow Plug
F1 Fuse 20 A Flat Fuse SAE J 1284
F2 Fuse 5 A Flat Fuse SAE J 1284
F3 Fuse 20 A Flat Fuse SAE J 1284
H2 Light in item S4 Operation indication (max. 2 W)
H4 LED max. 20 mA Flame indication (option)
K1 Relay (in item A2) Master relay
K2 Relay (in item A2) for circulation pump
K5 Relay for vehicle blower
M1 Motor Combustion air fan
M2 Motor Circulation pump
M3 Motor Vehicle blower

Item Nomenclature Remark

P1 Test Unit for diagnosis
R Resistor Resistor for H4
S1 Switch for Circulation Pump for separate switch-on
S4 Switch ON / OFF
S5 Isolation Switch 1-pole or 2-pole Emergency off switch electr. or pneum.
S6 Switch on Conveyor Facility to plus or minus
V106 Transistor in item A2
V107 Transistor in item A2
V108 Transistor in item A2
X1 Connection 12-pole on item A1
X4 Connection 2-pole
Y Dosing Pump

7 Circuit Diagrams Thermo 90

704

Fig. 704 Circuit Diagram Automatic Control for Thermo 90 S, 12 and 24 V with Standard Timer

ϑϑ

Temperature coding (temperature at water outlet):
see table page 302

Timer P2:
with plus at connection 10 = permanent operation in instant heating
without plus at connection 10 = heating period programmable

= (10 min to 120 min);
= basic setting 120 min

2

4

bl
br
ge
gn
gr
or
rt
sw
vi
ws

Wire colors

blue
brown
yellow
green
gray
orange
red
black
violet
white

Wire gauges

< 7.5 m 7.5 - 15 m

0.75 mm

2

1.0 mm

2

1.5 mm

2

2.5 mm

2

4.0 mm

2

1.5 mm

2

1.5 mm

2

2.5 mm

2

4.0 mm

2

6.0 mm

2

Item Nomenclature Remark

A1 Heater Thermo 90 / Thermo 90 S
A2 Control Unit
B1 Flame Sensor
B2 Temperature Sensor
B3 Temperature Limiter
B4 Room Thermostat
E Glow Plug
F1 Fuse 20 A Flat Fuse SAE J 1284
F2 Fuse 5 A Flat Fuse SAE J 1284
F3 Fuse 20 A Flat Fuse SAE J 1284
H1 Symbol for “Heating” in Display Operation indication

(in item P1 or P2)
H3 Light Symbol illumination (in item P1 or P2)
H6 LED red (in item P2) Illumination instant heat switch,

standby indication, on indication
K5 Relay for vehicle blower
M1 Motor Combustion air fan
M2 Motor Circulation pump
M3 Motor Vehicle blower

Item Nomenclature Remark

P2 Standard Timer (1531) for pre-timed operation
S8 Switch Button Instant heat switch remote control
X1 Connection 12-pole on item A1
X3 Connection 12-pole on item P2
X5 Connection 12

-pole

X6 Connection 12

-pole Diagnosis
X11 Connection 12-pole on item A2 (ST 1)
X12 Connection 12-pole on item A2 (ST 2)
X13 Connection 12

-pole on item A2 (ST 3)
Y1 Dosing Pump

Thermo 90 7 Circuit Diagrams

705

Fig. 705 Circuit Diagram Automatic Control for Thermo 90 S-TRS, 24 V

ϑϑ

Temperature coding (temperature at water outlet):
see table page 302

2

bl
br
ge
gn
gr
or
rt
sw
vi
ws

Wire colors

blue
brown
yellow
green
gray
orange
red
black
violet
white

Wire gauges

< 7.5 m 7.5 - 15 m

0.75 mm

2

1.0 mm

2

1.5 mm

2

2.5 mm

2

4.0 mm

2

1.5 mm

2

1.5 mm

2

2.5 mm

2

4.0 mm

2

6.0 mm

2

Item Nomenclature Remark

A1 Heater Thermo 90 / Thermo 90 S
A2 Control Unit
B1 Flame Sensor
B2 Temperature Sensor
B3 Temperature Limiter
B4 Room Thermostat
E Glow Plug
F1 Fuse 20 A Flat Fuse SAE J 1284
F2 Fuse 5 A Flat Fuse SAE J 1284
F3 Fuse 20 A Flat Fuse SAE J 1284
H2 Light in item S4 Operation indication (max. 2 W)
H5 Lamp, at least 1.2 W On indication conveyor equipment
K5 Relay for vehicle blower
M1 Motor Combustion air fan
M2 Motor Circulation pump
M3 Motor Vehicle blower
S4 Switch ON / OFF
S5 Isolation Switch 1-pole or 2-pole Emergency off switch electr. or

pn

eum.

Item Nomenclature Remark

S7 Switch conveyor equipment to Plus
X1 Connection 12-pole on item A1
X5 Connection 12-po

le

X6 Connection 12-po

le Diagnosis
X11 Connection 12-pole on item A2 (ST 1)
X12 Connection 12-pole on item A2 (ST 2)
X13 Connection 12-po

le on item A2 (ST 3)
Y1 Dosing Pump
Y2 Solenoid valve for conveyor equipment

7 Circuit Diagrams Thermo 90

706

Fig. 706 Circuit Diagram Automatic Control for Thermo 90 S-TRS, 24 V without Auxiliary Drive

ϑϑ

Temperature coding (temperature at water outlet):
see table page 302

2

bl
br
ge
gn
gr
or
rt
sw
vi
ws

Wire colors

blue
brown
yellow
green
gray
orange
red
black
violet
white

Wire gauges

< 7.5 m 7.5 - 15 m

0.75 mm

2

1.0 mm

2

1.5 mm

2

2.5 mm

2

4.0 mm

2

1.5 mm

2

1.5 mm

2

2.5 mm

2

4.0 mm

2

6.0 mm

2

Item Nomenclature Remark

A1 Heater Thermo 90 / Thermo 90 S
A2 Control Unit
B1 Flame Sensor
B2 Temperature Sensor
B3 Temperature Limiter
B4 Room Thermostat
E Glow Plug
F1 Fuse 20 A Flat Fuse SAE J 1284
F2 Fuse 5 A Flat Fuse SAE J 1284
F3 Fuse 20 A Flat Fuse SAE J 1284
H2 Light in item S4 Operation indication (max. 2 W)
K5 Relay for vehicle blower
M1 Motor Combustion air fan
M2 Motor Circulation pump
M3 Motor Vehicle blower
S4 Switch ON / OFF
S5 Isolation Switch 1-pole or 2-pole Emergency off switch electr. or

pne

um.

Item Nomenclature Remark

X1 Connection 12-pole on item A1
X5 Connection 12

-pole

X6 Connection 12

-pole Diagnosis
X11 Connection 12-pole on item A2 (ST 1)
X12 Connection 12-pole on item A2 (ST 2)
X13 Connection 12

-pole on item A2 (ST 3)
Y1 Dosing Pump

Thermo 90 8 Servicing

801

8 Servicing

8.1 General

This section describes t he servicing pr ocedures that may
be performed with the heater installed.

8.2 Work on the Heater

Prior to performing any work, it is mandatory to disconnect
the vehicle battery main lead. As long as the heate r is
in operation or in run-down, the battery main supply must
no

t be disconnected due to the danger of overheating
resulting in a response of the overheat protection . Wh en
performing extensive repairs on the heater, a complete
removal is advisable. After work on the heating circuit,
a coolant mixture consisting of water and anti-fre e ze
mu

st be replenished in accordance with manufacturer

instru

ctions followed by a careful bleeding of the heating
circuit.
When performing repairs requiring a relocation of the
installation pos

ition, the relevant installation instructions
and the vehicle-specific installation proposal have to be
observed.

8.3 Work on the Vehicle

CAUTION

In the vicinity of the heater, a temperature of 130° C must
no

t be exceeded under any circumstances (e.g. during

body paint work).

8 Servicing Thermo 90

802

8.4 Heater Test Run

WARNING

The heater must not be operated, not even with timer, in
en

closed areas like garages or workshops not equipped

with an exhaust venting facility.

8.5 Servicing

Before or after each heating season the following
servicing should be performed to maintain the he at er 's
functional reliability:

• Clean heater exterior (prevent the ingress of water).

• Examine electrical connections for corrosion of
c

ontacts and for security.

• Check exhaust combustion air lines for damage and
for

foreign matter and contamination.

• Check fuel lines and fuel filter for leakage.

• Check coolant circuit and circulation pump for
le

akage.

• Check hoses for cracks.

• Replace fuel filter if installed.

Thermo 90 8 Servicing

803

NOTE

Manufacturer mounts control unit of
heaters Thermo 90 S to combustion
air fan.

With Check Valve and Thermostat

Without Check Valve

1 Heat Exchanger,

Vehicle Heating System

2 Blower Switch

Vehicle Heating System
3 Relay for Vehicle Blower
4Timer
5 Fuse Box in Vehicle
6 Check Valve with Drain Hole
7 T-Junction
8 Vehicle Engine
9 Heater Unit

10 Circulation Pump
11 Water Pump
12 Radiator
13 Regulating Valve
14 Control Unit
15 Exhaust Muffler
16 Dosing Pump
17 Combustion Air In take Line
18 Thermostat

Cable Loom
Fuel Line
Exhaust Line
Coolant Circuit

8 Servicing Thermo 90

804

Fig. 801 Example for Heater Installation in Lorry

8.6 Visual Inspections and Installation
Regulations

8.6.1 Connection to the Vehicle's Cooling
System

In thermostat circuits only thermostats opening at < 65° C
are to be used.

The installation of the heater should be in a location as
low as possible to ensure self-venting of the heater and
ci

rculation pump. This applies in particular for the

circulation pump, which is not self-sucking.
The heater is to be connec

ted to the cooling system
according to Fig. 801. The amount of coolant in the
cooling system must be at least 6 litres.

As a rule, the coolant hoses supplied by Webasto
to

gether with the heater are to be used. Otherwise the

ho

ses must at least meet the requirements of DIN 73411.
The hoses must be routed without kinking, and for prop er
venting where possible in an upwards direction.

Hose connections must be sec

ured with hose clamps to

prevent slippage.

NOTE

Hose clamps must be torqued to 1.5 Nm (clamps
pr

eviously in use) or to 5.0 Nm (new, wide clamps).

Prior to first operation of the heater or after replacement
of the coolant, bleed the cooling circuit. Heater and lines
ha

ve to be installed so that a static venting is guarantee d.
Insufficient venting during heating operation may cause

fa

ilure due to overheating.

Proper venting is indicated by a circ

ulation pump almost
noiseless in operation. Insufficient venting during heating
operation may cause release of the resettable
temperature limiter.

8.6.2 Connection to the Vehicle's Fuel System

Fuel is tapped from the fuel reservoir of the vehicle or from
a separate fuel container.

The rated pressure at the fuel tapping location is shown
in the following table.

Fig. 802 Fuel Supply

previous new

Permissible fuel feed

height H (m)

at max. permissible over-

pressure (bar) in fuel tank

0.00 0.20

1.00 0.11

2.00 0.03

Permissible fuel suction

heig

ht S (m)

at max. permissible low

pressure (bar) in fuel tank

0.00 – 0.10

0.50 – 0.06

1.00 – 0.02

max. 3 m

i ø 2 mm

i ø 2 mm

S

H

i ø 2 mm

l

1

l

1

i ø 2 mm

l

2

l

2

HG

HG

l1 + l2≤ 10.0 m
l

1

≤ 1.2 m

l

2

≤ 8.8 m

Thermo 90 8 Servicing

805

8.6.2.1 Fuel Tapping

Fuel tapping must be from the fuel reservoir or from a
sep

arate tank (Figs. 803, 804, and 805). This separate

fuel tapping avoids an influence on the pressure.

Fig. 803 Webasto Fuel Tank Tap

* Use fuel tank tap only on metal fuel tanks

Fig. 804 Fuel Tapping from Plastic Tank

(

tapping via fuel drain plug)

Fig. 805 Fuel Tapping from Plastic Tank

(tap

ping via fitting plate)

NOTE

The fitting plate must be made of sheet metal.

Vehicles with Fuel Engines

In combination with carburettor or fuel injection engines
with

return line the heater's fuel system integration must

be in the return.
Carburettor engines without return line must

have the
heater integrated in the fuel supply between the vehicle's
fuel tank and fuel pump.

NOTE

• A fuel supply line can normally be identified by an

installed fuel

filter.

• If an exhalation vessel is installed in the vehicle's

fuel system, fuel tapping must be upstream of the
exh

alation vessel.

For fuel tapping from the supply or return line only the
specific

Webasto fuel tap, e.g. Ident. No. 470 910 for
Ø 8 mm may be used. The fuel tap must be mounted so
that th

e air or gas bubbles can escape towards the fuel
tank. Air or gas bubbles may build up in the vehicle fuel
line in case of a leak in the vehicle's carburettor or fuel
pump or when environmental temperatures are higher
than the fuel evaporation temperature.

> 25 mm

25

Hole Pattern

Gasket

Plastic Tank

Gasket

Tank Fitting Plate

Fuel Tank Tap

8 Servicing Thermo 90

806

The fuel tap should not be located in the engine
compartment because the radiation of en g ine hea t ma y
cause gas bubbles to build up in the fuel lines causing
malfunctions in the combustion operation.

When installing the heater in vehicles with fuel injection
system the

fuel pump's location within or outside the fuel
tank must be investigated first.
If the fuel pump is fitted insid

e the fuel tank, the fuel may
be tapped only from the return line ensuring that the return
line is routed almost to the tank floor. If this is not the case
the fuel line may be lengthened.
In case of a fuel pump mounted externally to the tank the
f

uel tap can be located between fuel tank and fuel pump.

8.6.2.2 Fuel Lines

Fuel lines may only be steel, copper, or plastic lines
mad

e of unhardened, light and temperature s

tabilised

PA 11 or PA 12 (e.g. Mecany

l RWTL) according to
DIN 73378. As in most cases a permanently rising fuel
line

routing cannot be ensured, the inner diameter must
not exceed a certain value. Starting from an inside
diameter of 4 mm, air or gas bubbles accumulate resulting
in malfunctions should the lines be descending or having
sags. The diameters specified in Fig. 802 ensure a
non-accumulation of air bubbles.

A descending line routing from the dosing pump to the
he

ater should be avoided.

Loose fuel lines must be secured in order to avoid
sa

gging. The installation must ensure protection against

stone impacts and undue temperatures (exhaust line).
The fuel line joints are to be secured against loosening

wit

h hose clamps.

Connection of 2 Pipes with Hose

The proper connection of fuel lines with hoses is shown in
Fig. 806

.

Fig. 806 Pipe/Hose Connection

8.6.3 Dosing Pump

The dosing pump is a combined delivery, dosing, and
shut-off system and is subject to certain installation
criteria (see Figs. 802 and 807).

Thermo 90, 12 Volt – Fuel

Thermo 90, 12 Volt and 24 Volt – Diesel DP 30

Installation Position Horizontal only

Fig. 807 Dosing Pump, Installation Location and

A

ttachment

correct

wrong

clamp

bubble bubble

0-90°

0°

0-90°

Thermo 90 8 Servicing

807

8.6.3.1 Installation Location

It is advantageous to mount the dosing pump in a cool
lo

cation as near as possible to the tank. The ambient
temperature must never exceed +20° C for fuel and
+40° C for Diesel operated installations at any time while
in o

peration. The maximum pressure at the tapping

location must be below 1.5 bar.
Dosing pump and fuel lines must not be installed in

loca

tions exposed to heat radiated by hot vehicle

components. A heat shield is to be provided as required.

8.6.3.2 Installation and Attachment

The dosing pump is to be attached with anti-vibration
mounts.

The installation location is limited according to
Fig. 807 to ensure sufficient self-venting capability. Due
to the danger of corrosion the plug

connection between
dosing pump and dosing pump cable loom may only use
Webasto original parts.

8.6.4 Fuel Filter

If there is the probability of contaminated fuel, only the
Webasto filter, Order No. 487 171, may be used. The
filter can be installed anywhere between the vertical and
ho

rizontal positions, but must be installed in the direction

of flow.

8.6.5 Combustion Air Supply

Combustion air must under no circumstances be
extracted from rooms with persons. The combustion air
inlet must not point towards the forward direction of
motion. It must be located so that no clogging by
contamination, impact of snow, or intake of splash water
is possible.

The combustion air intake line (inner diameter at least
30 mm) may have a length from 0.5 m to 5 m with several
be

nds of a total of 360°. Smallest bending radius is

45 mm.
The combustion air inlet must not be located abov e th e

exh

aust outlet.

NOTE

The combustion air intake line is to be routed in a
downwards

direction. If this is not possible, a water drain

hole (4 mm Ø) must be provided at the lowest point.
If the heater is located near

the fuel tank in a common
installation compartment, combustion air must be taken
in from, and the exhaust routed to, the exterior. The
feed-throughs must be splash waterproof.

If the heater is located in a closed installation box,
a vent port of at least 6 cm

2

is required. If the temperature
in the installation box exceeds the permitted ambient
temperature of the heater (see Technical Data), the vent
port must be enlarged consulting Webasto.

8.6.6 Exhaust Line

The exhaust line (inner diameter 38 mm) may have a
length from 0.5 m to 5 m and be routed with several bends
(a total of 360°, smallest bending radius 85 mm). The
exhaust muffler is mandatory and to be mounted near the
heater.

In order to ensure the angle of 90° ± 10°, an attachment
is required not further than 150 mm away measured from
the

exhaust pipe end.

Fig. 808 Exhaust Muffler, Direction of Flow

The exhaust pipe outlet opening must not point in the
dir

ection of motion (see Fig. 808).

The exhaust pipe outlet opening mu

st be located so as not

to allow clogging by snow or mud.
Rigid exhaust-line pipes can be mode of unalloyed or

allo

yed steel, but must have a minimum wall thickness of

1.0 mm. Flexible exhaust pipes must be made only of
alloyed steel. The exhaust pipe is secured to the air heater
with a clamp. For further requirements refer to official
regulations.

For Thermo 90 TRS only: For official regulations
concerning the exhaust pipe installation refer to Technical
Information E3 - 5.10 (Order No. 776 623).

10°

10°

Exhaust exit direction
nearly vertical 90° ± 10°

8 Servicing Thermo 90

808

8.7 Removal and Installation

CAUTION

In installed condition, only

the following removal and
disassembly procedures are allowed as long as the top
cover is accessible for removal and sufficient space for
removal is available:

– replacement of circulation pump
– replacement of temperature limiter
– replacement of temperature sensor
– replacement of combustion air fan
– replacement of control unit (Thermo 90 S)

8.7.1 Heater, Removal and Installation

8.7.1.1 Removal

1. Disconnect battery terminal leads.

NOTE

On heater Thermo 90 S with control unit flanged
to combustion air fan only connectors X12 and X13
r

equire disconnection from control unit.

2. Remove top cover.

3. Disconnect plug of cable loom from heater.

4. Disconnect fuel inlet on heater.

5. Loosen hose clamps and di

sconnect coolant hoses

from heater.

6. Disconnect connections of combustion air intake and

ex

haust outlet on heater.

7. Remove three nuts and washers from heater mount.

8. Remove heater.

8.7.1.2 Installation

1. Locate heater in installation position and secure with

th

ree nuts and washers.

2. Reconnect coolant hoses and secure with hose

clam

ps. Torque tighten clamps with 5 Nm.

3. Secure connection for fuel inlet on heater.

4. Secure connections for combustion air inlet and

ex

haust outlet on heater.

NOTE

On heater Thermo 90 S with control unit flanged to
com

bustion air fan reconnect connectors X12 and

X13 to control unit.

5. Connect plug of cable loom to heater.

6. Plug on top cover and arrest.

7. Reconnect battery terminal leads.

8. Bleed fuel supply system.

9. Bleed coolant circuit.

8.7.2 Replacement of Circulation Pump

NOTE

The procedure for replacement of the circulation pump is
iden

tical with the heater removed or installed.

Replacement is to be performed in accordance with 9.2.2.

8.7.3 Replacement of Temperature Limiter

NOTE

The procedure for replacement of the temperature limiter
is

identical with the heater removed or installed.

Replacement is to be performed in accordance with 9.2.3.

8.7.4 Replacement of Temperature Sensor

NOTE

The procedure for replacement of the temperature se nsor
is

identical with the heater removed or installed.

Replacement is to be performed in accordance with 9.2.4.

8.7.5 Replacement of Combustion Air Fan

NOTE

The procedure for replacement of the com b us tio n air fan
is

identical with the heater removed or installed.

Replacement is to be performed in accordance with 9.2.5.

8.8 First Operation

After installation of the heater, the fuel supply system
and the cooling circuit must be thoroughly bled observing
th

e vehicle manufacturer's instructions. During the test
run of the heater all connections are to be checked for
leakage and tight fit. Should the heater during operation
assume an error lock-out condition, perform trouble­shooting (see Section 5).

Thermo 90 8 Servicing

809

Page free for notes

Thermo 90 9 Repair

901

9 Repair

9.1 General

This section describes the repairs that may be performed
on the heater Thermo 90 when removed. Any further
disassembly will void the warranty.
For re-assembly only Webasto-authorised spare parts kits
ar

e to be used.

9.1.1 Work on Components afterDisassembly

CAUTION

All gaskets located between disassembled components
mu

st always be replaced and discarded.

9.1.1.1 Cleaning

• All disassembled components must be cleaned.

9.1.1.2 Visual Inspection

• Examine all components for damages (cracks,
d

eformation, wear, etc.) and replace as necessary.

• Examine connectors and wiring for corrosion,
loose contacts, wrong crimping, etc. and repair as
necessary

.

• Check terminals for corrosion and contacts for
se

curity. Repair as required.

9 Repair Thermo 90

902

9.2 Disassembly and Assembly

9.2.1 Electrical Connections (Fig. 901)

9.2.1.1 Disconnecting Electrical Connections
(Connection X1)

NOTE

All electrical connections are joined in the connector.
Prior to removal of a component, the relevant electrical
c

onnections first have to be disconnected.

On heater Thermo 90 S with flanged combustion air fan
co

nnector X1 on heater and connection X12 on control
unit must be disconnected and reconnected after making
electrical connections.

1. Remove top cover from heater.

2. Using removal tool (hook end) withdraw lock

wedge

from connector.

3. Using removal tool (screw driver end) press down
r

elevant locking tab and keeping tab depressed

withdraw cables from connector.

9.2.1.2 Making Electr

ical Connections

1. Slide cable into relevant contact pocket until locked.

2. Using removal tool (screw driver end) insert lock
we

dge in connector and press in until locked.

3. Fit top cover.

Fig. 901 Electrical Connections

Thermo 90

Lock Wedge

Locking Tab
(12 off)

Top Cover

Removal Tool

Supplier of Removal Tool
(Order No. DT RT1)

Compagnie Deutsch GmbH
Fraunhoferstr. 11b
82152 Martinsried
Tel. 0 89 / 8 99 15 70
Fax 0 89 / 8 57 46 84

NOTE

One of the newer models Thermo 90 shown. Older
models have the cable of the temperature limiter located
on the side.
Heater Thermo 90 S may have the control unit located on
the combustion air fan.

Thermo 90 9 Repair

903

9.2.2 Replacement of Circulation Pump

9.2.2.1 Removal

1. Remove heater (see 8.7.1.1).

2. Disconnect electrical conn

ections (see 9.2.1.1).

3. Remove screws (4, Fig. 902).

4. Remove clamp (3) and circulation pump (2).

5. Perform procedures on components after
disasse

mbly (see 9.1.1).

9.2.2.2 Installation

1. Apply acid free grease (Vaseline) to gasket
(1

, Fig. 902)

2. Bring circ ula tio n pu m p (2 ) in ass em b ly pos itio n an d
sec

ure using clamp (3) and screws (4).

3. Torque screws (4) to 3 Nm ± 10%.

4. Make electrical connections (see 9.2.1.2).

5. Install heater (see 8.7.1.2).

Fig. 902 Replacement of Circulation Pump

Thermo 90

NOTE

One of the newer models Thermo 90 shown.
Older models have the cable of the temperature
limiter located on the side.
Heater Thermo 90 S may have the control unit
located on the combustion air fan not affecting
the replacement of the circulation pump.

1 Gasket
2 Circulation Pump
3Clamp
4Screw (2)

1

2

3

4

9 Repair Thermo 90

904

9.2.3 Replacement of Temperature Limiter

9.2.3.1 Removal

NOTE

Perform the following procedure only when the tempera­ture limiter needs replacement.
A functional check has to be performed when the temper­ature limiter is installed.

1. Remove heater (see 8.7.1.1).

2. Disconnect electrical co

nnections (see 9.2.1.1).

3. Remove clamp (2, Fig. 903) and withdraw protective
ca

p (1).

4. Using screw driver, lever off retaining clip an

d remove

temperature limiter (3).

5. Perform procedures on components after
dis

assembly (see 9.1.1).

NOTE

Whenever the temperature limiter is removed, it must be
re

newed.

9.2.3.2 Installation

CAUTION

Wrong installation will caus

e melting of the heat

exchanger.

1. Insert the temperature limiter (3, Fig 903) into the heat
ex

changer (4) and press down retaining clip.

NOTE

Make sure the retaining clip is

heard to click fully in
place. Only then will the temperature limiter be in proper
installation position.
If clip does not audibly engage

• clean seat of the temperature limiter on the heat

ex

changer

• clean groove on heat exchanger

• ensure that the locking cams are present on both

side

s of the spring. Renew temperature limiter if

necessary.

2. Fit protective cap (1) and secure with clamp (2).

3. Torque tighten hose clamp with 1 Nm ± 10%.

4. Make electrical connections (see 9.2.1.2).

5. Install heater (see 8.7.1.2).

9.2.4 Replacement of Temperature Sensor

9.2.4.1 Removal

1. Remove heater (see 8.7.1.1).

2. Disconnect electrical connections (see 9.2.1.1).

WARNING

Escaping hot coolant may cause burns.

3. Unscrew temperature sensor (6, Fig. 903) and
re

move together with O-ring (5).

4. Perform procedures on components after
dis

assembly (see 9.1.1).

9.2.4.2 Installation

1. Apply acid free grease (Vaseline) to O-ring
(5

, Fig. 904).

2. Screw temperature sensor (6) with O-ring (5) into
h

eat exchanger (4) and torque tighten with

1.5 Nm ± 10%.

3. Make electrical connection

s (see 9.2.1.2).

4. Install heater (see 8.7.1.2).

Thermo 90 9 Repair

905

Fig. 903 Replacement of Temperature Limiter and Temperature Sensor

Thermo 90

6

5

1

2

3

4

1 Protective Cap
2 Clamp
3 Temperature Limiter
4 Heat Exchanger
5 O-Ring
6 Temperature Sensor

NOTE

One of the newer models Thermo 90 shown.
Older models have the cable of the temperature
limiter located on the side. Heater Thermo 90 S
may have the control unit located on the
combustion air fan not affecting the replacement
of the temperature limiter and temperature
sensor.

9 Repair Thermo 90

906

9.2.5 Replacement of Combustion Air Fan

9.2.5.1 Removal

1. Remove heater (see 8.7.1.1).

2. Disconnect electrical conne

ctions (see 9.2.1.1).

3. Remove screws (2, Fig. 904).

4. Pull combustion air fan (1) from burner head (4) and
r

emove together with profiled packing ring (3).

NOTE

On heater Thermo 90 S with flanged control unit
r

emove control unit as required.

5. Perform procedures on components after
dis

assembly (see 9.1.1).

9.2.5.2 Installation

NOTE

Locate packing ring (3, Fig. 904) properly; do no t
sq

ueeze.

1. Bring combustion air fan (1) with new profiled
pack

ing ring (3) in assembly position and secure with

screw

s (2).

2. Torque tighten screws (2) with 3 Nm ± 10%.

NOTE

On heater Thermo 90 S with flanged control unit install
control unit as

required.

3. Make electrical connection

s (see 9.2.1.2).

4. Install heater (see 8.7.1.2).

Fig. 904 Replacement of Combustion Air Fan

Thermo 90

Thermo 90 S

Control Unit

1

2

3

4

1

NOTE

One of the newer models Thermo 90 shown.
Older models have the cable of the
temperature limiter located on the side.

1 Combustion Air Fan
2 Screw (2)
3 Profiled Packing Ring
4 Burner Head

Thermo 90 9 Repair

907

9.2.6 Replacement of Burner, Flame Sensor,
and Glow Plug

9.2.6.1 Removal

1. Remove heater (see 8.7.1.1).

2. Remove combustion air

fan (see 9.2.5.1).

3. Remove screw (5, Fig. 905) and washer (4).

4. Remove nuts (10) and withdraw bracket.

5. Withdraw grommets (11 and 12) from slots in housing

of com

bustion tube (3).

6. Withdraw grommet (13) and burner (1) from burner

hea

d and remove together with swirl ring (2).

7. Pull flame sensor (7) and glow plug (6) out of burner

(1

) and remove.

8. Perform burner visual inspect

ion for assessment of

condition (see 5.3).

9. Perform procedures on components after

disasse

mbly (see 9.1.1).

9.2.6.2 Installation

1. Locate swirl ring (2, Fig. 905) on burner (1).

2. Carefully and fully insert flame sensor (7) and glow

plug

(6) into burner against stop and slide grommets
(11 and 12) down slots in housing of combustion
tube (3).

3. Position burner (1) and grommet (13) in burner
hea

d (3).

CAUTION

When performing the following step ensure that cables of
flame

sensor (7) and glow plug (6) are routed as shown in

figure.

4. Slide insulation (9) onto bracket and locate
bracket (8) in assembly position.

NOTE

Route cables of flame sensor and glow plug as shown
in Figure!

5. Secure bracket (8) using nuts (10). Torque nuts to
3 Nm ± 10%.

6. Secure fuel line with screw (5) and washer (4). Torque
screw

to 3 Nm ± 10%.

7. Mount combustion air fan (see 9.2.4.2).

8. Make electrical connections (see 9.2.1.2).

9. Install heater (see 8.7.1.2).

Glow Plug

Flame Sensor

9 Repair Thermo 90

908

Fig. 905 Replacement of Burner, Flame Sensor, and Glow Plug

Thermo 90

1Burner
2 Swirl Ring
3 Burner Head
4 Washer
5Screw

6 Glow Plug
7 Flame Sensor
8 Bracket

9 Insulation
10 Nut (2)
11 Grommet
12 Grommet
13 Grommet

NOTE

One of the newer models
Thermo 90 shown.
Older models have the cable of
the temperature limiter located
on the side.
Illustration is also applicable
for heater Thermo 90 S.

11

12

6

7

8

9

10

13

1

3

5

4

2

Thermo 90 9 Repair

909

9.2.7 Replacement of Burner Head

9.2.7.1 Removal

1. Remove heater (see 8.7.1.1).

2. Remove combustion air

fan (see 9.2.5.1).

3. Remove burner, flame sensor, and glow plug
(see 9.2.6.1).

4. Remove attachment screw of V-clamp (2, Fig. 906)
and

pull off clamp.

5. Withdraw burner head (1) from heat exchanger (3)
a

nd remove.

6. Perform procedures on components after
disasse

mbly (see 9.1.1).

9.2.7.2 Installation

NOTE

Burner head and exhaust outlet pipe

can still be aligned

during installation in vehicle.

1. Insert burner head (1, Fig. 906) into heat exchanger
(

3), align as necessary and secure with V-clamp (2).

2. Torque attachment screw of V-clamp to 3 Nm ± 10%
as re

quired.

3. Install burner, flame sensor, and glow plug
(se

e 9.2.6.2).

4. Install combustion air fan (see 9.2.5.2).

5. Install heater (see 8.7.1.2).

Fig. 906 Replacement of Burner Head

Thermo 90

1 Burner Head
2V-Clamp
3 Heat Exchanger

1

2

3

NOTE

One of the newer models Thermo 90 shown. Older
models have the cable of the temperature limiter located
on the side.
Illustration is also applicable for heater Thermo 90 S.

9 Repair Thermo 90

910

9.2.8 Replacement of Heat Exchanger

9.2.8.1 Removal

1. Remove heater (see 8.7.1.1).

2. Remove circulation pump (see 9.2.2.1).

3. Remove temperature limiter (see 9.2.3.1).

4. Remove temperature sensor (see 9.2.4.1).

5. Remove combustion air fan (see 9.2.5.1).

6. Remove burner, flame sensor, and glow plug
(see 9.2.6.1).

7. Remove burner head (see 9.2.7.1).

8. Remove connector and connector housing.

9. Perform procedures on components after
dis

assembly (see 9.1.1).

9.2.8.2 Installation

1. Clip connector housing onto heat exc

hanger and

engage connector in connector housing.

2. Install burner head (see 9.2.7.2).

3. Install burner, flame sensor, and glow plug
(see 9.2.6.2).

4. Install combustion air fan (see 9.2.5.2).

5. Install temperature sensor (see 9.2.4.2).

6. Install temperature limiter (see 9.2.3.2).

7. Install circulation pump (see 9.2.2.2).

8. Install heater (see 8.7.1.2).

Thermo 90 10 Packaging/Storage and Shipping

1001

10 Packaging/Storage and

Shipping

10.1 General

The heater and its components shipped to Webasto
Thermosysteme GmbH for inspection or repair are to be
cleaned and packaged so that they are protected against
damage during handling, transportation, and storage.

CAUTION

Should a complete heater assembly be shipped it must be
totally emp

tied. When packaging or shipping it must be

ensured that no fuel or coolant is able to escape.
The coolant pipe joints are to be sealed with plugs.
In storage, ambient temperatures detailed in Section 4

mu

st not be exceeded.

10 Packaging/Storage and Shipping Thermo 90

1002

Page free for notes