SKODA Self Study Program 25 – Air conditioning of the FELICIA and OCTAVIA SSP-25-Octavia-climatronic

You will be familiar with the refrigerant circuit of an air conditioning
system from the manual air conditioning of the FELICIA and OCTAVIA.
The fundamental design of an air conditioning system was explained in
Self Study Programme No. 10, while Self Study Programme No. 11
presented the specific air conditioning system in the FELICIA.

The technical perfection of an air conditioning system is the Climatronic.
The main highlight of this version is the electronic control, which performs
the task of blending the cooled and heated air to the desired comfort
temperature, a task which is performed manually on the conventional air
conditioning system.
This also is why the system is called Climatronic.

The principal parameters of the electronic control are the constant
comparison of the temperature between set and actual for the purpose of
automatically regulating the temperature of the air flowing in, of the air
volume and the distribution.

Climatronic

E

S

This fully automatic air conditioning system is presented to you in this Self
Study Programme.
It provides you with information regarding the controls, the operation and
self-diagnosis.

2

Contents

Components 4

Control Unit 6

Control Panel 7

Survey of Systems 10

Temperature Control 12

Temperature output values
Location of temperature sensors

Sensors 14

Actuators 21

12
13

New System Control 24

Air Flow 28

Diagram of Refrigerant Circuit 30

Radiator Fan Circuit 33

Compressor Control 34

Self Diagnosis 36

Function Diagram 38

Climatronic
Fan control
Legend

Test Your Knowledge 44

38
40
41

You will find notes on inspection and
maintenance, setting and repair instructions
in the Workshop Manual.

Service

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Service

3

Components

The manual air conditioning

The manual air conditioning and the heater unit
are described in Self Study Programme 15 ­SKODA OCTAVIA.

A comparison with the Climatronic as a reminder:
– The comfort level in the vehicle is controlled

manually by the driver.

– The flaps for the air flow,

the temperature flap,
the central flap,
the footwell/Defrost flap,
are adjusted by bowden cables.

– The fresh air/recirculated air flap is operated

electrically.

– The recirculated air mode is limited

mechanically to certain positions of the rotary
switches.

Fresh air/recirculated air flap

SP25-60

SP25-61

The Climatronic

– The comfort level (climate in the interior of the

car) is regulated automatically by the control
unit (regulation of temperature and control of
the air volume).

– This is achieved by integrating the appropriate

sensors and positioning motors (actuators) at
the air conditioning unit.

– The fresh air/recirculated air mode and also

the ram air pressure flap are operated by a

common electric motor.
– The central flap is operated electrically.
– The system has a self-diagnosis capability.

Ram air pressure flap

Fresh air/recirculated air flap

SP25-30

SP25-1

4

Location of Climatronic
components (with refrigerant
circuit)

This general view indicates the installation points
in the engine compartment or interior:

1 Compressor
2 Condenser
3 Receiver/drier
4 Expansion valve
F14 Coolant temperature warning switch

(overheating)
F129 Air conditioning pressure switch
G17 Ambient temperature sensor
G56 Dash panel temperature sensor
G89 Fresh air intake duct temperature sensor
G107 Sunlight penetration photo sensor
J255 Climatronic control unit
J293 Radiator fan control unit
N25 Air conditioning magnetic clutch

(G65)* High-pressure sensor

(only with new system control, then

replaces F129)

4

F129

(G65)*

G89

G107

J255
+G56

F14

3

2

J293

N25

1

G17

SP25-20

This general view shows the components located
at the AC unit:

G89 Fresh air intake duct temperature sensor
G192 Footwell vent temperature sensor
J126 Fresh air blower control unit
V2 Fresh air blower
V68 Temperature flap positioning motor
V70 Central flap positioning motor
V71 Ram air flow flap and recirculated air flap

positioning motor
V85 Footwell/Defroster flap positioning motor

G192

V85

V68

V70

G89

V71

V2

J126

SP25-21

5

Control Unit

Control unit with operating and
display unit

Climatronic control unit J255

AUTO

ECON

CLIMATRONIC

Temperature sensor blower
V42

Function

The Climatronic control unit is supplied with
information from the electrical and electronic

components (sensors). This information is
processed in accordance with the set values
stored in the control unit. The output signals of
the control unit then operate the electrical
components (actuators).

The Climatronic control unit J255 is located
directly at the operating and display unit E87.
Both units form a single component which cannot
be disassembled.

The temperature sensor for the interior
temperature of the car is known as the "dash
panel temperature sensor" and is integrated in
the control unit.

A blower for extracting the air inside the control
unit is located directly at the temperature sensor.

Dash panel temperature sensor
G56

The temperature sensor is positioned in the air
flow of the blower in order to avoid incorrect
measurements.

The control unit features a fault memory.
This makes it possible to rapidly determine
whether a component has failed or whether an
open circuit exists, by means of the self-diagnosis
facility.

A fault which has a sustained effect on the
operation of the Climatronic, is stored and
displayed.
The fault is displayed when the ignition is
switched on by the entire display of the display
unit flashing for about 15 seconds.

No matter what type of fault occurs, the
Climatronic control unit maintains the set
operation in the emergency mode.

Operating and display unit
E87

SP25-6

6

Control Panel

Display for defrost, windshield, recirculated air,
air flow direction

Display of ambient temperature

Display of selected blower setting

Pushbutton for
defrosting windshield

Display of interior temperature

Display of selected operating
mode:

AUTO Automatic mode
ECON Cooling system off

Pushbutton for
automatic mode

Pushbutton for
recirculated air mode

Pushbuttons for
slower blower setting and
entire system "OFF"
and also
faster blower setting
(stepless control)

Pushbutton for air flow to head area

SP25-7

ECON pushbutton =
Cooling system off

Pushbutton for "colder" and

Pushbutton for "warmer"
(graduated control)

Pushbutton for air flow to footwell

7

Control Panel

Climatronic functions

°

The pushbuttons can be pressed either to alter
the desired interior temperature or to override the
Automatic mode in order to switch off the air flow,
the air volume, the cooling system or the entire air
conditioning system.

Automatic mode

ECON mode

Knowledge of the special features of how the
system operates is important for conducting
specific service measures.
This is also important in discussions with the
customer regarding operation of the system.

When the ignition is switched on, the Climatronic
operates in the automatic mode.
The selected interior temperature is regulated
fully automatically by altering the flow of air into
the interior of the car, as well as the blower speed
and the air distribution. It is possible to vary the
automatic control by means of the pushbuttons.

SP25-8

If the ECON button is pressed, the cooling system
is switched off. In this case, only the heating
system is controlled automatically, without the air
being cooled. The desired interior temperature is
rapidly reached and maintained at a constant
level.
The desired interior temperature, however, can
never be lower than the ambient temperature.
The ECON mode switches off automatically if the
pushbutton for defrosting the windshield is
pressed. To reactivate the ECON mode, once
again press the ECON button. The ECON mode
is also switched off when the AUTO mode is
switched on.

Selected interior temperature

8

SP25-9

SP25-10

The interior temperature can be selected to any
desired temperature using the "colder" and
"warmer" pushbuttons. The temperature selected
remains stored until a different setting is made.
The interior temperature can be set within the
range of +18
The system is controlled automatically within this
range.

C to +29 ° C.

Note:
The system is not controlled automati-

°

cally if a temperature below 18

°

higher than 29
In these limit settings, the Climatronic
operates constantly at its maximum
cooling or heating capacity.
These limit ranges appear in the dis­play panel as "LO" (below 18
"HI" (higher than 29

C is selected.

°

C).

C or

°

C) or

Blower speed

Switching off the system

It is possible to override the automatic control and
to vary the blower speed in all the programme
settings.

The current blower speed is displayed by means
of a bar chart.

By varying the blower speed, the air flow supplied
to the interior of the car is practically increased or
reduced.

SP25-11

The entire system is switched off by repeatedly
pressing the "lower blower speed" pushbutton
until the end of the display.

In this case the readout "OFF" appears in the
display.

This function should only be used in exceptional
cases, for example if there is a fault in the air
conditioning system.

Defrost setting

Recirculated air setting

SP25-12

SP25-13

If the pushbutton for defrosting the windshield is
pressed, the same symbol as on the pushbutton
appears in the display.
The ECON mode is switched off automatically in
this switch position.
This setting is used for defrosting the windshield
or preventing it from misting up. This also
provides a means of boosting the demisting and
defrosting effect for the windshield, for example,
before setting off if persons wearing damp
clothing get into the car.

To activate the recirculated air mode, press the
recirculated air pushbutton. The same symbol as
on the pushbutton appears in the display.

When this mode is activated, air is extracted from
the interior of the car without any supply of fresh
air from the outside, in the same way as with the
conventional heating/ventilation and manual air
conditioning system.

SP25-14

The recirculated air mode is switched off by once
again pressing the same pushbutton.

9

Survey of Systems

Sensors

Sunlight penetration photo sensor
G107

Dash panel temperature
sensor G56 with temperature
sensor blower V42

Ambient air temperature
sensor G17

Fresh air intake duct
temperature sensor G89

Footwell vent temperature
sensor G192

Air conditioning pressure switch F129
or high-pressure sensor G65 (with
new system control)

CLIMAtronic

AUTO

ECON

CLIMATRONIC

Additional signals:

- Vehicle speed signal

- Engine speed signal

- Stationary time signal

Coolant temperature warning
switch (overheating) F14

Radiator fan thermoswitch F18

10

v
n

t

h

Climatronic control unit J255
and operating and display
unit E87

Actuators

Footwell/Defroster flap
positioning motor V85 with
potentiometer G114

Central flap positioning motor V70
with potentiometer G112

AUTO

ECON

Temperature flap positioning
motor V68 with potentiometer G92

Ram air flow flap positioning
motor V71 and recirculated air
flap with potentiometer G113

Fresh air blower control unit J126
with fresh air blower V2

Additional signals:

- Engine control unit

- Control unit with display unit
in dash panel insert

Diagnostic connector T16

Magnetic clutch N25

Radiator fan
control unit J293

Radiator fan V7 and
auxiliary fan V35

SP25-15

11

Temperature Control

Temperature output values

Influence of sunlight

penetration on interior

°

°

°

°

Ambient temperature in

measured in front left of front end

Interior temperature in

measured in middle of vehicle at dash panel

Automatic temperature control

When the Climatronic system is operated,
different temperature conditions and driving
states are taken into account.

In addition to the various control variables of
the air conditioning, the system of course also
compares the actual temperatures with the
desired set temperature.

There are two measuring points for the actual
temperatures (both on the inside as well as on the
outside) and these are located at different points.

It is possible to vary the control of the system
in line with individual wishes in respect of
temperature, air flow, blower speed.

C,

Set temperature in

stored in Climatronic control unit

C,

C in interior of vehicle -

Ambient temperature sensors

The ambient temperature is one of the basic
parameters for controlling the temperature of the
system.
The ambient temperature is detected constantly
at two measuring points, independent of each
other.

The temperature/resistance characteristics of
both temperature sensors is identical.

The Climatronic control unit analyses the results
of the measurements supplied by the two ambient
temperature sensors.

The lower of the two temperatures measured is
used for the temperature control.

Ambient temperature in ° C,

measured in fresh air intake duct

Air temperature in

measured in outlet duct of AC unit

C,

12

If one of the sensors fails, the remaining
temperature supplied is used as the control
variable.
If both temperature sensors fail, a fixed
temperature is adopted by the system.

Location of the temperature sensors

Sunlight penetration photo
sensor G107

Fresh air intake duct
temperature sensor G89

Ambient air temperature
sensor G17

Interior temperature sensors

The interior temperatures selected and measured
are further basic parameters for automatic control
of the temperature.

The temperature inside the car is detected by two
separate interior temperature sensors.

It is the sensors which supply the information to
the Climatronic control unit regarding the actual
temperature in the interior of the car, while an
additional sensor detects the temperature of the
air flowing out of the heating/air conditioning unit.

Dash panel temperature
sensor G56

Footwell vent temperature
sensor G192

SP25-22

Sunlight penetration as a control variable

In addition to the ambient temperature, the level
of comfort felt by the occupants of the car is also
influenced by the heat created inside the car by
the direct penetration of the sun's rays.

The light striking a photo sensor is analysed in
the Climatronic control unit and the temperature
control is varied accordingly.

If one of the sensors fails, a fixed value is adopted
as the control variable.
The air conditioning system continues to operate.

13

Sensors

Dash panel temperature sensor G56
with blower temperature sensor V42

The temperature sensor is integrated directly in
the control unit and supplies the actual interior
temperature to the Climatronic control unit.
It is located in the air flow of the blower for
extracting the interior air.

The blower is operated by the operating and
display unit.
It extracts the interior air in order to avoid any
incorrect measurements at the temperature
sensor.

Use of signal

The measured value is used for a comparison
with the set value.
The temperature flap and the fresh air blower are
controlled accordingly.

Dash panel temperature
sensor G56

Blower temperature sensor V42

CLIMATRONIC

°

°

AUTO

ECON

SP25-6

Effects in the event of signal failure

If the signal is not received, a substitute value of

C is adopted. The air conditioning system

+24
continues to operate.
The temperature sensor has a self-diagnosis
capability.

Footwell vent temperature sensor
G192

What is measured is the temperature of the air
which flows out of the heating/air conditioning unit
(and flows into the interior). The temperature is
detected by means of a temperature-responsive
(negative temperature coefficient) resistor.
When the temperature drops, the electrical
resistance increases.

Use of signal

The signal is analysed in the Climatronic control
unit. It is used for controlling the defrost/footwell
air flow and the air delivery of the fresh air blower.

Effects in the event of signal failure

In the event of a signal failure, the control unit
calculates a substitute value of +80
The air conditioning system continues to operate.
The temperature sensor has a self-diagnosis
capability.

SP25-26

NTC resistor

C.

14

Ambient temperature sensor G17

The temperature sensor is positioned in the front
end of the vehicle.
It detects the actual temperature of the outside air
(ambient temperature).

Use of signal

The Climatronic control unit varies the position of
the temperature flap and the speed of the fresh
air blower in line with the temperature measured.

Effects in the event of signal failure

In the event of a signal failure, the temperature
supplied by the fresh air intake duct temperature
sensor G89 is used as a substitute.
If this temperature sensor also fails, the system
continues operating by adopting a substitute
temperature of +10
is possible in this case.
The temperature sensor has a self-diagnosis
capability.

C. No recirculated air mode

SP25-24

°

Fresh air intake duct temperature
sensor G89

The temperature sensor is positioned directly in
the fresh air intake duct.
It is the second measuring point for the actual
outside air temperature (ambient temperature).

Use of signal

The Climatronic control unit varies the position of
the temperature flap and the speed of the fresh
air blower in line with the temperature measured.

Effects in the event of signal failure

In the event of a signal failure, the temperature
measured by the ambient air temperature sensor
G17 is used as a substitute.
The temperature sensor has a self-diagnosis
capability.

SP25-25

15

Sensors

Sunlight penetration photo sensor
G107

The temperature control of the air conditioning
system is influenced with the aid of the sunlight
penetration photo sensor.

This sensor detects the direct penetration of the
sun's rays on the vehicle occupants.

Function

The sunlight passes through a filter and an optical
element before striking a photo diode. The filter
has the same effect as sun glasses and prevents
the sunlight damaging the photo diode.

The photo diode is a light-sensitive
semiconductor element. If no sunlight penetrates
as far as the photo diode, only a slight current is
able to flow through the diode.
If the sunlight penetration intensifies, the flow
of current increases. The greater the sunlight
penetration, the higher is the current which flows
through the diode.

Consequently, the Climatronic control unit is
able to deduce that the sunlight penetration has

intensified from the increase in the current and
can vary the interior temperature accordingly. The
position of the temperature flap and the speed of
the fresh air blower are controlled accordingly.

SP25-70

Housing cover

Filter

Optical
element

Photo diode

Housing

Effects in the event of signal failure

The Climatronic control unit operates with an
assumed fixed value.

Self-diagnosis/Fault message

Open circuit/short circuit to positive.
Short circuit to earth.

16

SP25-62

Compensating for position of sun

Function if sunlight is striking vehicle at an
oblique angle

The occupants' sense of heat is increased
particularly if the sunlight penetrates the vehicle
from the front at an angle and thus is shining
directly on the occupants of the vehicle.

The optical element ensures that a greater
portion of the sunlight is deflected onto the photo
diode if the light penetrates the vehicle at an
angle.
The cooling capacity of the system is increased in
order to compensate for the greater effect of heat
on the body.

Filter

Optical element

Photo diode

SP25-63

Function if sunlight is striking vehicle directly
from above

The roof of the car acts as a shield when the
sunlight strikes the vehicle directly from above.

The optical element deflects less light to the
photo diode. It is possible to reduce the cooling
capacity of the air conditioning system as the
occupants of the car are not exposed to the direct
sun's rays.

Electric circuit

J225 Climatronic control unit
G107 Sunlight penetration photo sensor
Pin 9 Signal earth
Pin 18 Signal

The optical element
intensifies the screening
effect when the sun is
positioned directly
above.

SP25-64

J255

20/18 12/9

G107

SP25-23

17

Sensors

Air conditioning pressure switch
F129

The air conditioning pressure switch constantly
monitors the pressures in the refrigerant circuit of
the Climatronic system.
It is a triple switch.

Its functions are required for safety reasons
(a similar type of switch is also fitted to the
manual air conditioning system).

Tasks and function

– The switch closes if the rising pressure is

greater than 1.6 MPa (16 bar). The radiator
fan is switched to the next higher stage by the
radiator fan control unit in order to achieve an
optimum condenser efficiency.

SP25-44

– The switch opens if the pressure is too high

(e.g. if engine cooling is inadequate) from a
pressure of 3.2 MPa (32 bar). The air
conditioning system is then switched off.

– The switch opens if the pressure is too low,

below 0.2 MPa (2 bar) - e.g. in the event of a
loss of coolant. The air conditioning system is
switched off.

It is possible to remove the pressure switch from
the refrigerant circuit without first of all having to
extract the refrigerant.

Self-diagnosis

The 0.2 MPa/3.2 MPa (2 bar/32 bar) operating
part of the pressure switch is tested in the self­diagnosis in function 02 - Interrogating fault
memory.
The 1.6 MPa (16 bar) operating part is not
included.

Note:
The coolant temperature warning
switch F14 is also incorporated in the
safety circuit for switching off the air
conditioning system.
The air conditioning system is
switched off by this component if the

coolant temperature rises to 119 °C,

and is switched on again once the

temperature has dropped to 112 °C.

Electric circuit

+

15

J255 J293

12/2 16b/2 10b/2 10b/8

F129

F14 Coolant temperature warning switch

(overheating)
F129 Air conditioning pressure switch
J255 Climatronic control unit
J293 Radiator fan control unit

106/2

F14

SP25-43

18

Additional signals: stationary-time
signal

The Climatronic control unit J255 is supplied with
information regarding the "stationary time of the
vehicle" from the control unit with display unit
J285 (in dash panel insert).

Stationary time = ignition off until engine is
restarted

This information is always provided when the
"restart" event occurs.

4

3

1/min x 1000

2

1

5

6

7

120

100

140

km/h

80

60

40

20

160

240

180

220

200

J285

Why is this information needed?

When the vehicle is stationary, the temperatures
measured by the ambient air temperature sensor
G17 and by the fresh air intake duct temperature
sensor G89 are influenced to a greater or less
extent by the heat radiated in line with the time
during which the vehicle is stationary.
The result is that the actual ambient temperature
of the vehicle may be falsified.

Consequently, the analysis electronics of the
Climatronic control unit does not use the "current
falsified" temperature measurements for the

temperature control, but the temperature
measurements which were detected during last
operation of the Climatronic system, before the
engine was switched off.

This makes it possible for the system to more
rapidly reach the "comfort temperature" and to
prevent any risk of undercooling.
This signal is also important, for example, when
driving in slow moving traffic or when in a traffic
jam if the engine is switched off.

Temperature
measured at
"ignition off"

J255

SP25-4

35 °C

21 °C

SP25-5

Temperature
measured at
"restart" as a result
of radiated heat

19

Sensors

Additional signal: vehicle speed "v"

The current signal of the vehicle speed is required
in order to control the ram air flow flap.

The signal used is that supplied by the
speedometer sensor G22 in the gearbox,
which also exists at the control unit with display
J285 where it is converted for controlling the
temperature. The signal passes along a direct
signal wire to the ram air flow flap positioning
motor V71.

The vehicle speed signal is also tested by the
self-diagnosis capability.

Faults are only detected if no vehicle speed signal
is measured within 4 minutes after the engine is
started during 5 driving cycles (start, driving at a
speed of more than 15 km/h, switching off engine.

4

3

1/min x 1000

2

1

5

6

7

120

100

140

km/h

80

160

60

40

20

240

180

220

200

J285

J255

V71/G113

SP25-41

Additional signal: engine speed "n"

The Climatronic control unit has to be provided
with information regarding the current engine
speed.

The engine speed is detected from the signal
which is supplied by the control unit with display
J285.

The air conditioning magnetic clutch N25 is
thereupon operated by the radiator fan control
unit, e.g. no engine speed signal = engine not
running, AC compressor is switched off.

The engine speed signal is displayed in the
self-diagnosis in function 08 - Reading measured
value block.

4

3

1/min x 1000

2

1

5

6

7

120

100

140

km/h

80

160

60

40

20

240

180

220

200

J285

J255

J293

20

N25

SP25-42

Fresh air blower V2 and fresh air
blower control unit J126

Task

The interior of the vehicle is supplied with the
necessary quantity of air by the fresh air blower.

The fresh air blower can be steplessly controlled.
The control voltage for the fresh air blower is

computed in the Climatronic control unit. The
fresh air blower is operated and controlled by
the fresh air blower control unit in line with this
voltage:

– stabilised voltage at earth side
– unstabilised voltage at positive side.

Actuators

SP25-53

Fresh air blower V2

The actual voltage at the fresh air blower is fed
back to the Climatronic control unit.
The blower speed is constantly adjusted by the
fresh air blower control unit in line with this
information.

The fresh air blower control unit features heat
sinks.
The air flow upstream of the evaporator
constantly flows around these heat sinks, which
has the effect of cooling the power components in
the control unit.

The current blower speed is shown in the display
of the operating and display unit in the form of a
bar chart.

Substitute function

No substitute function.
In the event of damage to the blower or control
unit, the compressor is switched off.

Heat sinks

Fresh air blower control unit J126

Electric circuit

J255

16b/16

16b/11

16b/14

SP25-45

Self-diagnosis

The fresh air blower and the control unit are
integrated in the self-diagnosis.

J126 V2

M

SP25-34

21

Actuators

Positioning motors
for temperature flap V68
for central flap V70
for footwell/defrost V85
with potentiometer

Task

The positioning motor for the temperature
flap is operated in line with the selected interior
temperature while the positioning motors for the
central flap and defrost are operated in line with
the selected air flow, and these in turn alter the
position of the flaps.
The motors are located close to the particular
shaft of the flap at the heating/air conditioning
unit.

SP25-27

All the motors are supplied with the appropriate
control signals by the Climatronic control unit.

Each motor features a potentiometer.
This signals the position of the flap to the control
unit by means of a feedback value.

Self-diagnosis

All the positioning motors are integrated in the

self-diagnosis.
The end positions are adaptive.
What this means is that you have to perform
function 04 - Basic setting after installing a new
motor.
When you this, the motors move to the end
positions and the system "learns" these positions.

Note:
The mechanism for altering position of
the flaps varies (arrangement of crank)
and is matched to the rotating angle of
individual flaps.
You should note this point when
replacing the positioning motors.

Crank of positioning motor

Electric circuit

M

V68/G92
V70/G112
V85/G114

J255

SP25-33

22

Ram air flow flap positioning motor
V71

The positioning motor is located at the heating/air
conditioning unit next to the fresh air intake duct.

Connection to fresh air/
recirculated air flap shaft

Task

The positioning motor alters the position of the
ram air flow flap and of the fresh air/recirculated
air flap.

This combined movement of the flaps is
performed by a drive plate by means of two
guide points.

The positioning motor is operated by the
Climatronic control unit as a function of vehicle
speed and fan speed.

The ram air flow flap is used to reduce the flow
cross-section in the intake duct at higher vehicle
speeds.
When this is done, the flow of fresh air remains
practically constant.
It is thus possible to more easily maintain the
interior temperature at a constant level.

The potentiometer (G113) in the positioning
motor signals the position of the ram air flow
flap to the Climatronic control unit by means of

a feedback value.

Drive plate

Guide points

SP25-28

Operating lever for ram
air flow flap

Electric circuit

Self-diagnosis

The positioning motor is integrated in the
self-diagnosis.
The end position is adaptive.
What this means is that you have to perform
function 04 - Basic setting after installing a new
motor.
When you this, the motors move to the end
positions and the system "learns" these positions.

M

V71/G113

J255

SP25-32

23

New System Control

On vehicles fitted with the 1.6-ltr./74 kW engine
and the 1.4-ltr./44 kW engine, the system for
monitoring the refrigerant circuit has been

J285

4

3

1/min x 1000

5

2

1

A

υ

J255/E87

6
7

120

100

140

km/h

80

160

60

40

20

240

T

tnvn

M

digital signal

T

180

v

200

220

n

KB
KK

p

KK (in)

technically modified with effect from Model Year

1999.
It is also envisaged for further engines in this form.

J220

PWM

G65

J293

new signal paths

The technical highlights:

– Coolant temperature warning switch F14

discontinued.

– The coolant temperature signal T

by the combination processor J218 in the
dash panel insert.

– The air conditioning pressure switch F129 is

discontinued.
The new high-pressure sensor G65 is used in
its place.

– The radiator fan control unit J293 has

undergone further technical development
and has been matched in functional terms to
the new high-pressure sensor. It is installed
together with the high-pressure sensor.
Distinguishing feature:
modified connector terminals

is supplied

M

SP25-59

– The radiator fan control unit and the engine

control unit analyse a pulse width-modulated
(PWM) signal supplied by the new high­pressure sensor.

List of range of signals

ϑA Ambient temperature (data message)

to ambient temperature display in

instrument cluster

n Engine speed (frequency-modulated)
v Vehicle speed (frequency-modulated)
tn Stationary signal (data message)
KB AC standby mode
KK AC compressor ON/OFF (bi-directional)
KK (in) AC compressor on
T Kühlmitteltemperatur
T

M

Coolant temperature

Coolant temperature warning lamp

(overheating)

p Pressure

o.k. = positive signal

not o.k. = no signal

24

High-pressure sensor G65

A new generation for monitoring the refrigerant
circuit.

The high-pressure sensor is an electronic
pressure sensor and is installed in the high­pressure line.

It detects the refrigerant pressure and converts
the physical quantity of pressure into an electric
signal.
In contrast to the air conditioning pressure switch,
it is not only that the defined pressure thresholds
are detected, but the refrigerant pressure is also
monitored throughout the entire operating cycle.

SP25-65

Use of signal

in engine control unit and
in radiator fan control unit

Substitute function

Advantages

The signals are analysed to detect
the engine load resulting from the air conditioning
system and the pressure conditions in the
refrigerant circuit.

The next higher stage of the radiator fan and of
the compressor magnetic clutch are switched on
and off by the radiator fan control unit.

If the radiator fan control unit detects that no
signals have been received, the compressor is
switched off for safety reasons.

– This enables the engine speed within the

idling range to be exactly matched to the
particular power consumption of the
compressor.

– The different radiator fan stages are switched

on and off offset by a brief time delay.
Consequently, any change in speed in the
radiator fan is scarcely felt when the engine is
idling.

Self-diagnosis "fault message"

Any fault at the high-pressure sensor is stored
memory of the engine electronics.

e.g.: 00819 High-pressure sensor G65

"Signal too small"

25

New System Control

Function of high-pressure sensor

Low pressure

PWM signal
Microprocessor

The refrigerant pressure is directed to a silicone
crystal. Depending on the pressure level, the
crystal is "misshapen" to a greater or lesser
extent.

A property of the silicone crystal is that its
electrical resistance changes when it undergoes
a change in shape. Consequently, any voltage
supplied to the silicone crystal also varies in line
with the pressure pattern.

This change in voltage is passed on at the
high-pressure sensor to a microprocessor
(integrated in the high-pressure sensor) and
converted into a pulse width-modulated (PWM)
signal.

At a low pressure the change in shape of the
crystal is only slight. Consequently, the voltage
applied to the crystal is matched only by a low
electrical resistance.

PWM signal

Period 20 ms

Pulse width 2.6 ms

Voltage
Silicone crystal

SP25-66

The microprocessor of the high-pressure sensor
outputs a slight pulse width when the pressure is
low.

The PWM signals are generated with a frequency
of 50 Hz.
This corresponds to a period of 20 ms = 100 %.

At a low pressure of 0.24 MPa, the pulse width is

2.6 ms.
This corresponds to 13 % of the period.

26

SP25-67

High pressure (rising)

At a high (rising) pressure, the shape of the
crystal alters to a greater extent, which in turn
results in an increase in the electrical resistance.

The voltage is reduced by the same ratio.

PWM signal
Microprocessor
Voltage
Silicone crystal

SP25-68

PWM signal

Period 20 ms

The pulse width increases in the same ratio to the
increasing pressure.

At a high pressure of 0.37 MPa the pulse width is
18 ms. This corresponds to 90 % of the period.

Pulse width 18 ms

SP25-69

Note:
It is possible to visualise the PWM
signal with the digital memory
oscilloscope of the new vehicle
diagnosis system VAS 5051.

27

Air Flow

Heat exchanger

Footwell/Defrost
positioning motor V85

Temperature flap
positioning motor V68

Central flap positioning
motor V70

Ram air flow flap

Fresh air/recirculated air
flap

Ram air flow
flap positioning
motor V71

Fresh air blower V2

Evaporator

Air flow

The air flow as well as the function of the blower
and the recirculated air mode of the Climatronic

are similar in design to the manual air condition­ing system of the OCTAVIA.
You can find a function description of this in
Self Study Programme No. 15 of the SKODA
OCTAVIA.

Ram air flow flap and fresh air/
recirculated air flap

Fresh air mode

In the fresh air mode, the ram air flow flap and the
fresh air flap are fully open at a vehicle speed of
less than 20 km/h.

SP25-39

A new feature of this system are the positioning
motors for each flap and for the ram air flow flap.
They are operated jointly with the fresh air/
recirculated air flap by a positioning motor.

The fresh air flows unobstructed into the interior.

28

SP25-35

Ram air flow mode

When the car is travelling at higher speeds, the
ram air flow flap prevents too much air flowing
into the passenger compartment.

The ram air flow flap is opened and closed in line
with the speed of the vehicle according to a
defined map.

The position of the ram air flow flap is also
influenced by the difference between the set and
actual temperatures in the passenger compart­ment. If the temperature difference is extremely
high, the opening cross-section remains open
even when vehicle speed rises in order to more
rapidly attain the desired temperature.

The ram air flow flap is closed in accordance with
the map from a defined vehicle speed.

SP25-36

Only a small portion of fresh air flows through the
remaining narrow gap to the fresh air duct and
into the passenger compartment, the fresh air
flow, however, remains practically constant.
This makes it possible to more easily maintain the
interior temperature at a constant level.

Recirculated air mode

Both flaps are closed in the recirculated air mode.
The fresh air supply is shut off.
In this mode, air is only extracted from the
passenger compartment.

SP25-37

Recirculated air

SP25-38

29

Diagram of Refrigerant Circuit

Diagram of refrigerant circuit of the
SKODA OCTAVIA

Expansion valve

Fresh air blower

Low-pressure
service connection

Evaporator

High-pressure
service connection

Receiver with drier

You will be familiar with the basic operating
principle of an air conditioning system from Self
Study Programme No. 10.

The Climatronic fitted to the OCTAVIA has the
same basic design of the refrigerant circuit:

– Self-regulating compressor
– Receiver with drier
– Expansion valve
– Condenser
– Evaporator (in heating/AC unit)
– 1 service connection each in high-pressure

– System filled with environmentally-compatible

High pressure

Low pressure

and in low-pressure part of the refrigerant
circuit

refrigerant R134a

Compressor with
magnetic clutch

Condenser

Radiator fan and
auxiliary fan

SP25-48

The radiator fan and an auxiliary fan ensure
proper cooling of the engine in the engine cooling
circuit and of the condenser in the refrigerant
circuit when the air conditioning system is
operating.

Protective circuits (mechanical/electrical) are
provided for protecting the entire operation of the
air conditioning system and of the vehicle engine.

All the safety precautions regarding carrying out
work on vehicles fitted with air conditioning and
on handling refrigerants apply in full to the
refrigerant circuit of the Climatronic system.

30

Expansion valve with internal
thermo head

The expansion valve is located directly upstream
of the evaporator between the high-pressure and
low-pressure sides of the refrigerant circuit,
exactly as on the FELICIA air conditioning
system.

Control unit

From condenser
(liquid)

Thermo head with
gas filling

The control unit is a compact design. All of the
refrigerant flowing back from the evaporator to
the condenser flows around the thermo head with
its gas filling.

Ball valve

To evaporator
(pressure-relieved)

Tappet rod

Pressure
compensating drilling

To compressor

Operating principle

The flow of liquid refrigerant is atomised at the
valve, the stress is released and it cools down.

The valve regulates the refrigerant flow in such a
way that the vapour does not become gaseous
until it reaches the evaporator, in line with the
heat flow.
The expansion valve is controlled thermostatically
for this purpose.

Diaphragm

Low-pressure
evaporator outlet

SP25-54

It features the control unit with thermo head and
ball valve for this purpose.
The thermo head contains a special gas filling on
the one side of the diaphragm.
The opposite side is connected by means of
pressure compensating drillings to the evaporator
outlet (low-pressure side).
The ball valve is operated by a tappet rod.

31

Diagram of Refrigerant Circuit

The variable valve opening (depending on the
evaporator temperature which exists) makes it
possible to achieve an alternating cross section of
the expansion valve.

Increase in cooling load results in - higher

temperature at evaporator outlet

consequently

Pressure rise (p

The cross section at the ball valve

is enlarged by means of the diaphragm

and tappet rod.

A greater quantity of refrigerant

flows to evaporator and absorbs heat

as it passes from the high-pressure

to the low-pressure side.

The air flowing through is cooled down

in the evaporator.

) of gas filling in thermo

a

head

p

a

SP25-55

SP25-56

p

b

If the temperature of the refrigerant at

the evaporator outlet drops, this results in a

pressure drop (p

) in the thermo head

b

The cross section at the ball valve and thus

the flow to the evaporator are reduced; a

smaller quantity of the refrigerant flows to the

evaporator.

32

SP25-57

SP25-58

Circuit of the fan for cooling the
engine/condenser

Radiator Fan Circuit

Operation of the fan is a basic condition for
proper function of the Climatronic system
(refrigerant circuit) and of the engine
(coolant circuit).
To ensure adequate cooling capacity, the
auxiliary fan V35 also runs when the air
conditioning is in operation. Radiator fan V7 and
auxiliary fan V35 ensure an adequate flow of
fresh air at the radiator and at the condenser.

Radiator fan V7 Auxiliary fan V35

Radiator fan control unit J293

Thermoswitch F18

The fan is controlled by the radiator fan control
unit J293.

Both fans are controlled in line with the
temperature of the coolant and with the pressure
in the refrigerant circuit.

Air conditioning pressure

switch F129

Monitoring functions

– Coolant temperature

The signal sensor is the radiator fan
thermoswitch F18.
The thermoswitch is located in the vehicle
radiator. Radiator fan without operation of
AC
1st stage on 92 ... 97 °C

off 84 ... 91 °C

2nd stage on 99 ... 105 °C

off 91 ... 98 °C

– Pressure in refrigerant circuit

The signal sensor is the air conditioning
pressure switch F129
at a pressure greater than 1.6 MPa (16 bar)
both fans operate in stage 2
at a pressure greater than 3.2 MPa (32 bar)
the air conditioning is switched off
at a pressure less than 0.2 MPa (2 bar) the
air conditioning is switched off

Operating combinations

– Air conditioning is switched on,

consequently compressor also switched on
and pressure in refrigerant circuit greater
than 0.2 MPa (2 bar) = both fans operate in
stage 1

– High pressure in refrigerant circuit greater

than 1.6 MPa (16 bar) and/or coolant
temperature greater than 99 °C = both fans
operate in stage 2

– If pressure in refrigerant circuit drops below

1.6 MPa (16 bar) and coolant temperature
is below 99 °C = both fans again operate in
stage 1

– Only the radiator fan operates when engine

is running with air conditioning off.

33

Compressor Control

Air conditioning magnetic clutch
N25

The magnetic clutch is operated by the
Climatronic control unit through the radiator fan
control unit.

It switches the compressor on or off.
In order to protect the engine (effect on engine

cooling) and the air conditioning system, the
compressor control not only integrates the control
components of the Climatronic system but also
the additional components of the coolant
temperature warning switch (overheating) F14
and the air conditioning pressure switch F129.

In addition, on a vehicle fitted with an automatic
gearbox, the kickdown signal is used for
switching the compressor off and on.
There are a number of switch-off conditions with
which it is important to be familiar for performing
service work.

SP25-49

AC magnetic clutch N25 Compressor

Compressor switch-off conditions

– Safety switch-off (through F129) if excessively

high pressure in refrigerant circuit

– Safety switch-off (through F129) if excessively

low pressure in refrigerant circuit
– No engine speed signal
– Air conditioning mode switched off with the

"minus" button for fresh air blower speed

(through E87)
– ECON mode (cooling system switched off

manually through E87)
– Ambient temperature below approx. 3 °C
– Automatic gearbox control unit (kickdown

function)
– Insufficiently low supply voltage (below 9.5 V)

– Safety switch-off (through F14) if excessively

high coolant temperature (disengaged at
119 °C, re-engaged at 112 °C)

– AC compressor switched off by engine control

unit (through Climatronic control unit)

– AC compressor switched off by automatic

gearbox control unit (through Climatronic
control unit)

– Safety switch-off if fresh air blower V2 or fresh

air blower control unit is faulty

Note:
Most of these switch-off conditions
can be tested by using the self­diagnosis, function 08 - Reading
measured value block.

34

Diagram of compressor control in
the integrated component system

The diagram of the compressor control illustrates
the influence of the main components regarding
the switch-off/switch-on conditions of magnetic
clutch N25 when the air conditioning/Climatronic

J...

Engine

CLIMATRONIC control unit

J255

Radiator fan control unit

J293

is operating.
In addition, the chart illustrates how the
components are integrated with the other
control units in the vehicle

E87

J217

(Kick-down)

F129

F14

N25

The Climatronic can therefore not be regarded as
a totally stand-alone system.

That is why the Climatronic control unit J255 is
linked over signal wires to the other vehicle
control units (engine control unit, automatic
gearbox control unit).

The Climatronic control unit "manages" the
information for the other linked control units and
transmits it in order to control the other systems
and components (see compressor switch-off
conditions).

SP25-50

Legend of diagram:

E87 Climatronic operating and display unit
F14 Coolant temperature warning switch

(overheating)
F129 Air conditioning pressure switch
J... Engine control unit
J217 Automatic gearbox control unit
J255 Climatronic control unit
J293 Radiator fan control unit
N25 Air conditioning magnetic clutch

35

Self Diagnosis

The Climatronic control unit features a fault
memory to enable any failure of the component in
the Climatronic system or an open circuit in the
wiring to be rapidly detected.

Self-diagnosis can be performed using the
vehicle system tester V.A.G 1552, the fault
reader V.A.G 1551 or with the vehicle diagnosis,
measurement and information system VAS 5051.

If faults occur in the sensors or components
monitored, the faults are stored in the fault
memory (permanent memory) with an indication
of the type of fault.

1

2

3

4

5

6

7

8

9

C

O

HELP

Q

V.A.G.

1552

202_CZ_002

SP17-29

If a fault which has a continuous influence on the
operation of the Climatronic system is stored, all
the symbols in the display panel of the operating
and display unit E87 flash for about 15 seconds
after the ignition is switched on.

The address word for self-diagnosis of the
Climatronic system is:

08 - AC/heating electronics

The following functions are possible:
01 - Interrogating control unit version

02 - Interrogating fault memory
03 - Final control diagnosis
04 - Basic setting
05 - Erasing fault memory
06 - Ending output
07 - Coding control unit
08 - Reading measured value block

SP25-46

It is necessary to code the Climatronic control unit
each time it is installed.
The coding varies according to the particular
country.

In addition, it is also necessary to initiate function
04 - Basic setting each time the positioning
motors are replaced.

36

This is done by moving the positioning motors
into the end positions. The Climatronic control
unit then stores the values of the potentiometers
of the positioning motors and thus adopts their
basic setting.

CLIMAtronic

AUTO

ECON

CLIMATRONIC

AUTO

ECON

v

n

t

h

SP25-47

All the components illustrated in colour are
monitored by the self-diagnosis.

The following additional signals

– stationary time signal "t
– vehicle speed signal "v"
– engine speed signal "n"

are also incorporated in the self-diagnosis.
The temperature sensor blower V42 is not

covered by the test.

Use of self-diagnosis

The Climatronic system is not controlled when
final control diagnosis is in progress.
Final control diagnosis should be performed
when the engine is not running,
ignition switched on and
Climatronic system switched off.

The ambient temperature should be at least
12 °C.

"

h

The control of the Climatronic system is in
operation in function 08 - Reading measured
value block.

Interrelationships between electrical and
mechanical causes of faults are basically
possible, just as in other vehicle components,
e.g. engine management systems.

What this means is that a positioning motor which
is indicated as being faulty, may be operating
completely properly electrically although it is
"jamming" mechanically.

A faulty lever connection of a positioning motor is
not detected electrically as the motor is still able
to operate freely.

Note:
Please refer to the Workshop
Manual OCTAVIA, Heating and Air
Conditioning, for the exact procedure
for self-diagnosis.

37

Function Diagram

Climatronic

30
15

X

31

V68

M

16a/10

20/8

G17

G56 V42 E87 L75 L76

12/8

20/18 16a/11

G107

K

M

12/1

J255

16a/3

20/10

G112G114G92

M

V85

16a/12

M

V70

16a/4

20/916a/2

38

31

30
15

31

X

c

v

n

16b/4 16b/6 20/13 20/1 12/11 16a/6 16a/7 12/3 16b/12

16a/5

16a/13

20/17

12/9

J285

12/7

t

h

12/8

20/5

16b/16

J126G192G89 V2G113

16b/11

16b/14

J220
J248
J361

16a/15

16b/10

J220
J248
J361

12/2 16b/2

F129

M

V71

in out

M

Refer to page 37 for the
designation of the components

a

b

31

SP25-2

39

Function Diagram

Radiator fan control

30
15

X

31

c

Connection to
display unit

10b/2 10b/8 4a/210b/6 4a/1 10b/10

D/15 D/30

S5
7,5A

10b/9 10b/4 4a/4 4a/3

S16
10A

15

A/+

S164
30A

J293

S180
30A

10b/7

F18

30
15

31

X

F14

Connection to
Climatronic
control unit
J255

a

b

31

V7

V35

M

in out

N25

M

31

SP25-3

40

Legend of function diagram

Components

The function diagram represents a simplified
current flow diagram.

It shows all the links of the Climatronic system
components including the radiator fan control
unit.

Additional signals

v Vehicle speed signal
n Engine speed signal
t

h

Colour coding

Stationary time signal

Input signal
Output signal
Positive
Earth
K diagnosis wire

A Battery +
D Ignition/starter switch terminal 30 or

terminal 15
E87 Climatronic operating and display unit
F14 Coolant temperature warning switch

(overheating)
F18 Radiator fan thermoswitch
F129 Air conditioning pressure switch
G17 Ambient air temperature sensor
G56 Dash panel temperature sensor
G89 Fresh air intake duct temperature sensor
G92 Potentiometer of temperature flap

positioning motor V68
G107 Sunlight penetration photo sensor
G112 Potentiometer of central flap positioning

motor V70
G113 Potentiometer of ram air flow flap

positioning motor V71
G114 Potentiometer of footwell/defrost flap

positioning motor V85
G192 Footwell vent temperature sensor
J126 Fresh air blower control unit
J220 Motronic control unit
J248 Diesel direct injection system control unit
J255 Climatronic control unit
J285 Control unit with display in dash panel

insert
J293 Radiator fan control unit
J361 Simos control unit
L75 Digital display illumination
L76 Pushbutton illumination
N25 Air conditioning magnetic clutch
S... Fuse with number
V2 Fresh air blower
V7 Radiator fan
V35 Right coolant fan (auxiliary fan)
V42 Temperature sensor blower
V68 Temperature flap positioning motor
V70 Central flap positioning motor
V71 Ram air flow flap positioning motor
V85 Footwell/defrost flap positioning motor

41

?

Test Your Knowledge

Which answers are correct?
Sometimes only one.
Perhaps also more than one - or all!

1. Which of the following statements regarding the Climatronic
system are correct?

A. The temperature is regulated electronically.
B. The electronics system is not able to take into account

individual wishes.

C. The temperature control is not able to compensate for

the effect of the sun's rays.

2. A recirculated air mode can be individually selected on the manually regulated air conditioning
system.

A. The Climatronic system does not have a recirculated air mode; a ram air pressure flap is

provided instead.

B. A recirculated air mode can be achieved on the Climatronic system by a combination of the

air flow and defrost settings.

C. A recirculated air mode can also be selected individually with the Climatronic system.

3. The ram air flow flap is used for
A. shortening the response time of the air conditioning control

B. avoiding wind noises in the AC unit at high speeds
C. reducing the flow cross section in the intake duct of the fresh air at high speeds.

?

4. What is the task of the dash panel temperature sensor?
A. Providing information to the Climatronic control unit regarding the temperature of the air

which is flowing through the dash panel vent.

B. Providing information to the Climatronic control unit regarding the intensity of the sunlight

above the dash panel.

C. Providing information regarding the interior temperature measured in the vehicle.

5. The temperature control takes into account the signals supplied by several temperature sensors.
Which answers are not correct?

A. Sunlight penetration photo sensor G107
B. Thermoswitch F18
C. Ambient air temperature sensor G17
D. Footwell vent temperature sensor G192

42

?

6. The fresh air blower V2
A. is also operated by the radiator fan control unit

B. is operated and controlled by the fresh air blower control unit in line with the calculated

control voltage

C. can be also set individually to any desired setting, in addition to the automatic control.

7. What are the operating conditions in which the radiator fan operates in stage 2?
A. Coolant temperature higher than 99 °C

B. High pressure in refrigerant circuit greater than 1.6 MPa (16 bar)
C. Coolant temperature warning switch (overheating) F14 operates

8. The Climatronic control unit is linked to form a single unit
A. with the radiator fan control unit

B. with the fresh air blower control unit
C. with the operating and display unit
D. with the dash panel temperature sensor.

9. Most of the Climatronic components have a self-diagnosis capability.
A. The Climatronic control unit features a fault memory for this purpose.

B. If a fault exists which has a continuous effect on operation of the Climatronic system, the

10. In certain environmental conditions, the Climatronic system may be switched off even though

symbols in the display unit come on and remain on.

C. If a fault exists which has a continuous effect on operation of the Climatronic system, the

symbols in the display unit come on for 15 seconds after the ignition is switched on.

there is no fault in the system.
A. Ambient temperature higher than 40 °C

B. Ambient temperature lower than 3 °C
C. Coolant temperature of engine higher than 119 °C

7. A., B.; 8. C., D.; 9. A., C.; 10. B., C.

1. A.; 2. C.; 3. C.; 4. C.; 5. B.; 6. B., C.;

Answers

C

M

I

N

O

R

C

I

ON

T

R

R

O

A

N

IC

C

L

I

M

A

A

M

I

L

C

I

L

C

SP25-51

43