Volkswagen T3 other 1987 User Manual
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Diagnostic Service Manuals
DOMETIC
Dometic
MANUAL REFRIGERATOR
DIAGNOSTIC SERVICE
MANUAL
The
Corporate Office
Technical Services
Dometic
Warranty
Department
Department
Corporation
2320 Industrial Parkway
Elkhart, IN 46515
219-295-5228
205 E. Fenn St.
LaGrange, IN 46761
219-463-2191
509 S. Poplar St.
LaGrange, IN 46761
219-463-4858
OS1286
8/89
D-l
NOTES:
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D-2
MANUAL REFRIGERATOR
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DIAGNOSTIC SERVICE ‘MANUAL
Table of Contents
Diagnostic Flow Charts
Page
No Operation . . . . . . . . . . . . .
No
12OV
No Gas Operation (Piezo Igniter)
AC Operation . . . . . . . . .
. . . .
No Gas Operation (Automatic Reigniter)
Operation and Diagnosis
Dometic Manual Refrigerators.
Glossary of Terms
Service Bulletins
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . .
D-4-l
D-4-2
D-4-3
. .
D-4-4
D-6-
1
D-8-l
D-9-l
D-3
MANUAL REFRIGERATOR
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DIAGNOSTIC FLOW CHART
NO OPERATION
A.
Check Supply Voltage
1. 110 Volt Plug
2. Wire Size
OK
B.
Check Fuse
C.
Check wiring
V
OK
\/
1
I~>1
NOT OK
NOT OK
Correct as Necessary
Correct as Necessary
>
Replace if Defective
>
Correct as Necessary
1
OK
DD.
Check Switch
E.
Check Thermostat
V
OK
NOT OK
NOT OK
>
Correct as Necessary
(Page D-6-20,
, Correct as Necessary
’
Continuity Check
Para.
66)
D-4-l
MANUAL REFRIGERATOR
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DIAGNOSTIC FLOW CHART
A.
1. Check AC Power
2. Refrigerator Plugged in
3. Breaker
4. Coach
Plug
OK
NO 120 VOLT AC OPERATION
~=I
Correct as Necessary
i
B.
Check Selector Switch
c.
Check Thermostat
w
NOT OK
OK
V
NOT OK
OK
I
D.
Check 120 Volt Heater
If
NOT OK
Correct as Necessary
(Page D-6-20,
Correct as Necessary
Continuity Check
Correct as Necessary
B
Ohm’s Reading
Bulletin
(Page D-9-l 4, D-9-l 5)
#28
Para.
66)
D-4-2
NO GAS OPERATION - Models Equipped with Piezo igniter
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.
Check Gas Supply
9
B.
Check Switch
.C.
v
I
OK
OK
MANUAL REFRIGERATOR
DIAGNOSTIC FLOW CHART
Correct as Necessary
NOT OK
>
(Page D-6-20,
Para
66)
Check Thermostat
OK
D.
Check Gas Pressure
Check Flue & Burner
V
OK
I
OK
F.
Check Piezo Resistance
I
NOT OK
NOT OK
NOT OK
NOT OK
Correct as Necessary
=>
Continuity Check
Correct as Necessary
>
>
>
(Page D-6-13,
Correct as Necessary
No Obstructions
Correct as Necessary
(Page D-6-l 8,
Para.
Para.
37)
58)
OK
G.
Check Piezo Electrode
,H.
Check Spark Gap
of Electrode to Burner
V
V
r
Replace ElectrodPara
>
(Page D-6-18,
I
OK
NOT OK
NOT OK
D-4-3
Correct as Necessary
>
(Page D-6-19,
Para.
Para.
58)
62)
MANUAL REFRIGERATOR
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DIAGNOSTIC FLOW CHART
NO GAS OPERATION - Models Equipped with Automatic Reigniter
A.
>
Check Gas Pressure
NOT OK
I
OK
Correct as Necessary
(Page D-6-13,
Para
37)
B.
Check Gas Supply
C.
Check 12 Volt D.C.
Supply
V
I
I
v
I
OK
OK
I
Check Switch
I
OK
_E.
Check Thermostat
NOT OK
NOT OK
NOT OK
NOT OK
Correct as Necessary
>
>
B
>
(Page D-6-14,
Correct as Necessary
Correct as Necessary
(Page D-6-20,
Correct as Necessary
Check for Continuity
Para.
Para.
40)
66)
OK
F.
Check Flue & Burner
,G.
Check Electrode
V
V
I
I
OK
NOT OK
NOT OK
Clean Assembly
>
Orifice as Necessary
Replace Electrode
>
(Page D-6-19,
&
Para.
62)
NOTES:
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D-5
OPERATION
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&
DIAGNOSIS
OF
DOMETIC
MANUAL REFRIGERATORS
D-6-1
This is Dometic’s Manual Refrigeration Diagnosis and Troubleshooting program. In this program
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(1)
we will discuss the way an absorption cooling unit operates, and the diagnostic procedures
used to troubleshoot the complete refrigerator system.
Before we begin extensive troubleshooting
procedures on the cooling unit, let’s take a few
minutes to see how it operates.
(3)
The sealed combustion unit contains a
(2)
mixture of ammonia, water and
inhibiting agent. After this solution is
introduced into the coils, this unit is
pressurized with hydrogen gas. When
this system is in operation, the ammonia vaporizes in the hydrogen atmosphere and absorbs heat from inside
the refrigerator.
a rust
THE ABSORPTION SYSTEM
GAS
TEMPERATURE
EXCHANGER
ABSORBER
EVAPORATOR
Lil I
VESSEL
D-6-2
BOILER
.
The cooling unit parts that accomplish this
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(4)
‘cooling’ or heat extraction process, include the:
Boiler or Generator
\
/
BOILER
PUMP
(5)
Condenser
l-------------
GAS
TEMPERATUR
EXCHANGER
------------
WATER
SEPARATOR
-l
I
I
I
I
I
_-.I
1
(6)
Evaporator
D-6-3
(7)
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Absorber
ABSORBER
Because the self-contained cooling unit
does not utilize an electric compressor
or pump, the cooling coils can be operated from a variety of heat sources. LP
gas, 120 volts AC and 12 volts DC
heating elements are the most commonly used heat sources for recreational vehicle applications.
THE ABSORPTION
TEMPERATURE
EXCHANGER
TEMPERATURE
EXCHANGER
SYSTEM
CONDENSER
EVAPORATOR
_
Before this cooling system can properly
(9)
extract heat from the cabinet of the
THREE REQUIREMENTS
FOR PROPER OPERATION
refrigerator, three requirements for proper refrigerator operation must be met.
These are precise heat, specified ventilation and proper leveling.
D-6-4
1. Level
2. Air Flow (Ventilation)
3. Heat
(10)
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We will now take a closer look at how the
cooling unit functions in normal operation.
When proper heat is supplied to the boiler,
ammonia vapor is produced and rises in the
siphon pump, carrying with it a weak liquid
ammonia solution. As seen from this drawing,
the siphon pump, or pump tube, is an internal
arrangement within the boiler section. The boiler
section utilizes the ammonia-water liquid solution in the absorber and as it is heated, turns
the solution into a strong ammonia vapor, which
is needed to operate the system. This strong
ammonia vapor rises from the pump tube to the
condenser coil.
Any deviation from the listed amount of
heat to the absorption system will alter the
ammonia to water ratio, which, in turn, will
decrease the cooling unit’s overall efficiency.
The weak ammonia solution which remains
behind is diverted to the top of the absorber
coils to perform a function that we will discuss
in further detail later in the program.
c---_-------____---------__----_-__-7
I
I
i
I------------------------~
WATER
ENSER
PUMP
/
P
I
1
I
(11)
The air that passes through the condenser fins,
from the venting system, removes heat from the
ammonia vapor, causing it to condense into a
strong liquid ammonia solution. As a liquid, it
then flows to the low temperature evaporator, or
freezer companment, where it comes into
contact with a hydrogen atmosphere. When this
occurs, the ammonia begins to evaporate which
draws heat from inside the freezer section, to
the rear of the cooling unit.
(12)
This heat is then dissipated out through the
upper vent, which allows the refrigerators
interior temperature to properly maintain food
storage requirements. Not all of the liquid
ammonia evaporates in the freezer. What is left
continues to evaporate as it flows to the high
temperature evaporator, or food storage com-
partment.
COLD INTERIOR
D-6-5
U
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As this process continues, the ammonia and
hydrogen vapors become intermixed and flow
downward into the absorber vessel. As the
ammonia vapor comes in close contact to the
liquid ammonia solution in the absorber vessel,
the ammonia is absorbed into the liquid
solution, allowing the hydrogen vapor to rise up
through the absorber coils. After this absorption
process, the vapor consists of mostly hydrogen
with some traces of ammonia.
3)
I--
I
1
I
I
I
I
I
I
To remove the remaining amounts of ammonia
vapor still present in the hydrogen, a
continuous flow of weak ammonia solution is
fed, by gravity, to the top of the absorber coil
from the boiler. As this weak ammonia solution
flows downward through the absorber, it
absorbs the ammonia vapor from the mixture,
allowing the hydrogen vapor to rise through the
absorber coil and return to the evaporator. With
the hydrogen returned to the evaporator and
the ammonia remixed into solution in the
absorber vessel, the cooling process can
continue.
Now that we have a basic understanding of
proper cooling unit flow and operation, let’s
take a step-by-step look at the three requirements for proper cooling unit operation. Please
note it is essential that these three requirements
be diagnosed before attempting to diagnose
the cooling unit. A problem with leveling, heat
input or ventilation may lead you to think that
the cooling unit is faulty, when actually it is not.
This
causes an
customer, and valuable shop time is wasted
because of incorrect diagnosis, By following
and checking the three unit requirements, costly
diagnostic errors can be eliminated.
increased expense to you, the
(14)
(15)
-------
I
---
__------
Ll_____i
THREE REQUIREMENTS
FOR PROPER OPERATION
1. Level
2.
Air Flow (Ventilation)
3. Heat
__A
I
D-6-6
Since the absorption system utilizes no
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(16)
mechanical pumps or compressors to circulate
the refrigerant within the system, proper leveling
is required to provide correct refrigerant flow in
the gravity-feed system. Without proper leveling,
refrigerant within the cooling coils will collect
and stagnate at certain areas. When this
happens the cooling process will stop.
(17)
On the older style cooling units equipped with
square boiler box covers, this condition can
cause permanent cooling unit failure. As we can
see from this drawing, square boiler box
cooling units utilize an exposed siphon pump
tube which will become excessively super-
heated in an out-of-level condition. This can
allow the rust inhibiting agent to chemically
break down and permanently block or restrict
the normal refrigerant flow through the pump.
Shaking, tipping or so called ‘burping the
refrigerator will not loosen or dislodge the
blockage. The only recommended service
procedure is to replace the cooling unit. To
prevent this occurrence, proper leveling is of
utmost importance when the RV is parked for
any length of time.
THREE REQUIREMENTS
FOR PROPER OPERATION
1.
Level
(18)
To level these units, the spirit or bubble level
should be placed in the approximate front and
center of the floor of the freezer compartment.
The coach should then be positioned so that at
least 3/4 of the bubble is within the required
mark while the refrigerator is in operation.
REMEMBER: Failure to property
boiler box can result in a lack of cooling or
permanent
the vehicle is moving, leveling is not critical as
the rolling and pitching movement of the RV will
keep the solution in motion, preventing the
solution from accumulating in the piping.
damage to the coding unit. When
level
a square
REFRIGERATOR IS TO BE LEVEL
--
-
m
-_C==Z
_
LEVELS
-5
D-6-7
In recent years
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type of cooling unit that utilizes an improved
siphon pump tube design which drastically
reduces the possibility of permanent damage to
the coils if operated in an out-of-level condition,
or too much heat is generated at the boiler
section. As we can see from this drawing, the
siphon pump tube is enclosed in the design
and is surrounded by a weak ammonia solution,
which will protect the pump tube from abnormally over-heating. This type of unit; however,
does not eliminate the need for proper leveling.
The unit still requires gravitational flow to
provide the proper cooling process, and if
leveling is outside the necessary limits, cooling
will dramatically slow down or stop completely.
The cooling coils are not normally damaged in
this fashion and once proper leveling is maintained, the cooling process will resume.
Dometic
has engineered a new
(19)
I
I
\
PUMP
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Spirit or bubble levels are no longer being
(20)
supplied with the new style refrigerators as the
RV or vehicle only needs to be leveled so it is
comfortable to live in, with no noticeable sloping
of the floor or walls. For diagnosis, the new
style
protection boiler system, can be differentiated
from the older style coils by the shape and
design of the outer boiler box cover on the rear
of the cooling unit. These units will incorporate
a circular metal cover,
cooling
while the older style utilizes a square
. . .
shaped enclosure.
and troubleshooting of these units in more
detail later in the program.
units that incorporate the
We will discuss diagnosis
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