Audi 2003 A8 Instruction manual

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Workshop Manual
Audi A8 2003 ➤
Air conditioning
Edition 09.2010
Service
Service Department. Technical Information

Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.
List of Workshop Manual Repair GroupsList of Workshop Manual
Repair GroupsList of Workshop Manual Repair Groups
Repair Group
87 - Air conditioning system
Technical information should always be available to the foremen and mechanics, because their
careful and constant adherence to the instructions is essential to ensure vehicle road-worthiness and
safety. In addition, the normal basic safety precautions for working on motor vehicles must, as a
matter of course, be observed.
Service
All rights reserved.
No reproduction without prior agreement from publisher.
Copyright © 2010 Audi AG, Ingolstadt A0051005620

Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.
Contents
87 - Air conditioning system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1 Safety precautions when working on vehicles fitted with an air conditioner and for handling
refrigerant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Safety precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Draining refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Working on refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.4 Painting work on vehicles fitted with an air conditioner . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.5 Further information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Notes on general repairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Note on vehicles with auxiliary heater (poor heating output) . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Notes on air conditioner self-diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3 Electrical checking of air conditioner components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 Servicing refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1 General view of components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2 Removing and installing air conditioner high-pressure sender G65 . . . . . . . . . . . . . . . . . . 10
3.3 Checking pressure signal from high-pressure sender G65 . . . . . . . . . . . . . . . . . . . . . . . . 10
3.4 O-rings for refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.5 Detaching compressor from holder/attaching on vehicles with 6-cyl. engine, 8-cyl. MPI engine
or 8-cyl. diesel engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.6 Checking activation signal for air conditioner compressor regulating valve N280 . . . . . . 16
4 Replacing compressor pulley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.1 Replacing pulley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.2 Detaching pulley from compressor/re-attaching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.3 Replacing pulley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.4 Detaching pulley from compressor/re-attaching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5 Components for control and regulation of air conditioner not located in passenger
compartment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.1 Components not located in passenger compartment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.2 Removing and installing dust and pollen filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.3 Dust and pollen filter with activated charcoal filter element . . . . . . . . . . . . . . . . . . . . . . . . 31
5.4 Cleaning air conditioner evaporator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.5 Removing and installing air quality sensor G238 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.6 Mode of operation of air quality sensor G238 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.7 Checking air quality sensor G238 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.8 Checking vent frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.9 Checking and cleaning plenum chamber water drain . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.10 Removing and installing intake housing with air flow flap . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.11 Removing and installing air flow flap control motor V71 with potentiometer G113 . . . . . . 45
5.12 Preparing adapter cables for control motor actuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
5.13 Removing and installing fresh air intake duct temperature sensor G89 . . . . . . . . . . . . . . 47
5.14 Removing and installing air recirculation flap control motor V113 . . . . . . . . . . . . . . . . . . . . 47
5.15 Removing and installing cover with air recirculation flap . . . . . . . . . . . . . . . . . . . . . . . . . . 52
5.16 Removing and installing fresh air blower V2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
5.17 Removing and installing fresh air blower control unit J126 . . . . . . . . . . . . . . . . . . . . . . . . 55
5.18 Removing and installing pump valve unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.19 Operation of solar roof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
6 Heated windscreen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
6.1 Operation of heated windscreen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
7 Electrical checking of components actuated by the air conditioner . . . . . . . . . . . . . . . . . . 65
7.1 Checking of heated rear window Z1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
7.2 Checking of heated seats and seat ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
7.3 Checking fuel-driven supplementary heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Audi A8 2003 ➤
Air conditioning - Edition 09.2010
Contents i

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7.4 Checking electric supplementary heater for rear footwell . . . . . . . . . . . . . . . . . . . . . . . . . . 69
7.5 Checking actuation of heated windscreen Z2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
8 Components for control and regulation of air conditioner located in passenger
compartment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
8.1 Components located in passenger compartment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
8.2 Removing and installing left centre vent control motor V110 . . . . . . . . . . . . . . . . . . . . . . 76
8.3 Removing and installing right centre vent control motor V111 . . . . . . . . . . . . . . . . . . . . . . 79
8.4 Removing and installing centre vent temperature sender G191 . . . . . . . . . . . . . . . . . . . . 79
8.5 Removing and installing sunlight penetration photosensor G107 . . . . . . . . . . . . . . . . . . . . 80
8.6 Removing and installing temperature sensor blower V42 . . . . . . . . . . . . . . . . . . . . . . . . . . 80
8.7 Removing and installing front operating and display unit, Climatronic control unit J255 . . 80
8.8 Removing and installing rear left footwell heater element Z42 / rear right footwell heater
element Z43 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
8.9 Removing and installing rear left centre console temperature sensor G311 and rear right
centre console temperature sensor G312 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
8.10 Removing and installing rear left vent warm air and cold air flap control motor V220 . . . . 85
8.11 Removing and installing rear right vent warm air and cold air flap control motor V221 . . 87
8.12 Removing and installing rear Climatronic operating and display unit E265 . . . . . . . . . . . . 87
8.13 Removing, checking and installing condensation drain hose . . . . . . . . . . . . . . . . . . . . . . . . 90
8.14 Air conditioning unit components located in passenger compartment . . . . . . . . . . . . . . . . 92
8.15 Removing and installing defroster flap control motor V107 . . . . . . . . . . . . . . . . . . . . . . . . 93
8.16 Removing and installing centre vent control motor V102 . . . . . . . . . . . . . . . . . . . . . . . . . . 95
8.17 Removing and installing front left defroster and chest vent shut-off flap control motor V200
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
8.18 Removing and installing front right defroster and chest vent shut-off flap control motor V199
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
8.19 Removing and installing left footwell flap control motor V108 . . . . . . . . . . . . . . . . . . . . . . 101
8.20 Removing and installing right footwell flap control motor V109 . . . . . . . . . . . . . . . . . . . . . . 103
8.21 Removing and installing temperature flap control motor V68 . . . . . . . . . . . . . . . . . . . . . . 105
8.22 Removing and installing left vent temperature sender G150 . . . . . . . . . . . . . . . . . . . . . . 106
8.23 Removing and installing right vent temperature sender G151 . . . . . . . . . . . . . . . . . . . . . . 107
8.24 Removing and installing evaporator output temperature sender G263 . . . . . . . . . . . . . . . . 107
8.25 Removing and installing rear left vent control motor V218 and rear right vent control motor
V219 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
9 Removing and installing heat exchanger of air conditioning unit . . . . . . . . . . . . . . . . . . . . 111
9.1 Preparation for heat exchanger removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
9.2 Removing and installing right (front passenger side) heat exchanger . . . . . . . . . . . . . . . . 112
9.3 Removing and installing left (driver side) heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . 116
10 Block diagram of air distribution system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
10.1 Air intake and air routing in air conditioning unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
10.2 Air routing and air distribution in passenger compartment . . . . . . . . . . . . . . . . . . . . . . . . . . 120
11 Checking cooling output of air conditioner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
11.1 Prerequisites for checking cooling output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
11.2 Checking cooling output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
11.3 Measures to be taken if readout does not match specification . . . . . . . . . . . . . . . . . . . . . . 128
11.4 Measures to be taken in the event of temperature increase downstream of evaporator . . 130
12 Checking heat output of air conditioner and operation of pump valve unit . . . . . . . . . . . . . . 132
12.1 Checking operation of pump valve unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
13 Servicing refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
13.1 Servicing refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
13.2 Detaching refrigerant lines at compressor/attaching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
13.3 Removing and installing compressor (basic information) . . . . . . . . . . . . . . . . . . . . . . . . . . 140
13.4 Removing and installing compressor (on vehicles with 8-cyl. FSI engine) . . . . . . . . . . . . 141
13.5 Detaching compressor from holder/removing and installing (on vehicles with 12-cyl.
engine) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
13.6 Removing and installing compressor (on vehicles with 10-cyl. engine, Audi S8) . . . . . . . . 153
Audi A8 2003 ➤
Air conditioning - Edition 09.2010
ii Contents

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13.7 Checking/replacing compressor drive unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
13.8 Unfastening and tightening compressor drive shaft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
13.9 Removing and installing compressor drive shaft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
13.10 Detaching drive plate with overload safeguard/attaching . . . . . . . . . . . . . . . . . . . . . . . . . . 163
13.11 Checking concentricity of drive plate with overload safeguard/adjusting . . . . . . . . . . . . . . 164
13.12 Unscrewing drive plate from compressor/screwing on . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
13.13 Removing and installing drive plate with rolling bearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
13.14 Detaching refrigerant lines from condenser/re-attaching . . . . . . . . . . . . . . . . . . . . . . . . . . 166
13.15 Removing and installing condenser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
13.16 Removing and installing restrictor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
13.17 Removing and installing reservoir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
13.18 Detaching refrigerant lines at evaporator connection/attaching . . . . . . . . . . . . . . . . . . . . . . 171
13.19 Removing and installing evaporator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
13.20 Capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
13.21 Starting up air conditioner after charging refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . 177
14 Removing and installing air conditioning unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
14.1 Removing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
14.2 Installing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
15 Dismantling and assembling air conditioning unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
15.1 Removing and installing covers in plenum chamber, fresh air blower and evaporator . . . . 183
15.2 Dismantling and assembling bottom part of housing and air distribution housing . . . . . . . . 187
15.3 Dismantling and assembling air distribution housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
Audi A8 2003 ➤
Air conditioning - Edition 09.2010
Contents iii

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Audi A8 2003 ➤
Air conditioning - Edition 09.2010
iv Contents

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87 – Air conditioning system
1 Safety precautions when working on
vehicles fitted with an air conditioner
and for handling refrigerant
The air conditioner assemblies and piping system are filled with
the following refrigerant:
1.1.1.2 tetrafluoroethane (CF3-CH2F or CH2F-CF3)
This refrigerant is currently known in Germany by the trade names
R134a, H-FKW 134a, SUVA 134a and KLEA 134a (other trade
names may be used in other countries).
1.1 Safety precautions
The following safety precautions are to be heeded in Germany for
this refrigerant (additional regulations may apply in other coun‐
tries).
The refrigerant circuit is to be drained first should repair work re‐
quire the refrigerant circuit to be opened ⇒ page 2 . All contact
with liquid refrigerant or refrigerant vapours is to be avoided.
Should refrigerant escape despite compliance with all safety pre‐
cautions, take care never to inhale the mixture of refrigerant and
air which forms.
Extraction systems are therefore to be switched on and use made
of rubber gloves and safety goggles.
Reason:
Intensive exposure to refrigerant would cause frostbite on unpro‐
tected parts of the body.
WARNING
It is advisable to keep an eye bath to hand.
Should liquid refrigerant come into contact with the eyes, rinse
them thoroughly with water for about 15 minutes.
Then apply eye drops and consult a doctor immediately, even
if no pain is felt.
The doctor should be informed of the type of refrigerant which
caused the frostbite.
Should refrigerant come into contact with other parts of the body
despite compliance with all safety precautions, these must like‐
wise be thoroughly rinsed without delay for at least 15 minutes
with cold water.
Although refrigerants do not represent a fire hazard, smoking,
welding, soldering and brazing are not permitted in areas exposed
to refrigerant.
Reason:
The high temperature of a naked flame or hot objects causes re‐
frigerant gas to undergo chemical decomposition. The inhalation
of the toxic decomposition products results in dry coughing and
nausea.
Audi A8 2003 ➤
Air conditioning - Edition 09.2010
1. Safety precautions when working on vehicles fitted with an air conditioner and for handling refrigerant 1

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permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.
1.2 Draining refrigerant circuit
Refrigerant must not be allowed to escape into the environment.
It should be extracted from the refrigerant circuit by means of a
suction unit or service station. The refrigerant removed is then
either to be re-processed on site or returned to the manufacturer
for proper disposal (different or additional regulations may apply
in other countries). For this reason, the vehicle is to be taken to a
workshop equipped with the necessary tools where the work can
be performed by appropriately qualified personnel ⇒ Air condi‐
tioner with refrigerant R134a .
Reason:
Should it escape into the earth's atmosphere, refrigerant R134a
will have a detrimental effect in terms of »global warming«.
Note
♦ Refrigerant R134a has far less of a greenhouse effect than
refrigerant R12.
♦ The refrigerant R134a does not affect the ozone layer in the
earth's atmosphere ( -R134a- is an H-FC with no chlorine
atoms). The depletion of the ozone in the upper atmosphere
is however only caused by the splitting of carbon-chlorine
bonds (as is the case, for example, with the refrigerant R12).
After draining the air conditioner, unplug the connector from the
air conditioner compressor regulating valve -N280- or from the
high-pressure sender -G65- .
Reason:
The air conditioner compressor regulating valve -N280- is then no
longer actuated and the compressor runs at idle. The compressor
is designed such that lubrication of the compressor components
is guaranteed by way of an internal oil circuit at idle (provided
there is sufficient refrigerant oil in the compressor).
1.3 Working on refrigerant circuit
Work on the refrigerant circuit is only to be performed in well ven‐
tilated areas. Care should be taken to ensure that there are no
inspection pits, shafts or cellar entrances within a radius of 5 me‐
tres. Extraction systems are to be switched on.
Reason:
The refrigerant which emerges is not only colourless and odour‐
less, but also heavier than air and therefore displaces oxygen.
Should refrigerant gas escape despite compliance with all safety
precautions, there will be a previously impercepible risk of as‐
phyxiation in poorly ventilated areas and inspection pits.
Note
The mixture of gas and air which forms when refrigerant gas es‐
capes is not to be inhaled. It must be extracted using suitable
extraction systems (workshop extractor).
Welding, brazing and soldering operations are not to be per‐
formed on air conditioner components when filled. The same
applies to welding and soldering work on the vehicle if there is a
risk that parts of the air conditioner could become warm.
Audi A8 2003 ➤
Air conditioning - Edition 09.2010
2 Rep. gr.87 - Air conditioning system

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Reason:
Heat generation causes considerable pressure to build up in the
system and this could lead to rupturing of the system.
Remedy:
Drain the refrigerant circuit ( ⇒ page 2 ).
Note
Damaged or leaking air conditioner components are not to be re‐
paired by welding or soldering, but should be replaced.
When servicing the air conditioner, all open components and pipe
connections are to be immediately re-sealed.
Reason:
Moisture will ingress into the air conditioner components if they
are left open for a lengthy period. If this is the case, air condition‐
ers cannot be re-filled without having to replace parts of the
system.
1.4 Painting work on vehicles fitted with an
air conditioner
When performing paintwork repairs, the temperature in the drying
booth or preheating zone must not exceed 80 °C.
Reason:
Heat generation causes considerable pressure to build up in the
system and this could lead to rupturing of the system.
1.5 Further information
♦ In the vehicle diagnostic, testing and information system -
VAS 5051 A- , „Guided fault-finding“ routine ⇒ "Guided fault-
finding" function of vehicle diagnostic, testing and information
system VAS 5051.
♦ The appropriate current flow diagrams can be found in the
Current flow diagrams, Electrical fault-finding and Fitting lo‐
cations binder ⇒ Current flow diagrams, Electrical fault finding
and Fitting locations.
♦ A label in the engine compartment indicates the refrigerant
used as well as the capacity.
♦ Further information on repair work for vehicles fitted with an
air conditioner and on handling refrigerant is stored in ⇒ Air
conditioner with refrigerant R134a .
Audi A8 2003 ➤
Air conditioning - Edition 09.2010
1. Safety precautions when working on vehicles fitted with an air conditioner and for handling refrigerant 3

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permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.
2 Notes on general repairs
DANGER!
Remove the appropriate fuse(s) before working on wiring.
Note
Disconnect batteries before starting electric welding work on the
vehicle ⇒ Electrical system; Rep. gr. 27
It is only permissible if so required by the pertinent safety regu‐
lations ( ⇒ page 2 ), or if parts of the air conditioner refrigerant
circuit have to be replaced, to drain and open the air conditioner
refrigerant circuit ( ⇒ page 2 ).
The air conditioner refrigerant circuit must remain closed during
all other normal vehicle repair operations.
Service work which can be performed on the heater and air con‐
ditioner without opening the refrigerant circuit is described in this
Workshop Manual ⇒ page 26 .
Note
The connections for the senders/switches described in this Work‐
shop Manual are fitted with a valve which closes automatically
when the switches are unscrewed. These switches can therefore
be replaced at any VW/Audi workshop without draining the re‐
frigerant circuit.
Air conditioner servicing work which requires drainage of the re‐
frigerant circuit and which thus cannot be performed at all Audi
and VW workshops is also described in this workshop manual
⇒ page 135 (for drainage of the refrigerant circuit, the vehicle is
to be taken to a workshop equipped with the necessary tools
where the work can be performed by appropriately qualified per‐
sonnel ⇒ Air conditioner with refrigerant R134a ).
2.1 Note on vehicles with auxiliary heater
(poor heating output)
In the event of problems with poor heat output, check the air con‐
ditioner heat output and operation of the pump valve unit
⇒ page 132 .
In the event of problems relating to poor or inadequate heat output
at low engine speeds on vehicles fitted with an auxiliary heater as
optional extra, check actuation of the auxiliary/supplementary
heater circulation pump -V55- by the supplementary heater con‐
trol unit -J364- ⇒ Auxiliary/supplementary heater; Rep. gr. 82
and ⇒ "Guided fault-finding" function of vehicle diagnostic, testing
and information system VAS 5051 (auxiliary heater guided fault-
finding).
♦ Actuation of the circulation pump -V55- increases the flow of
coolant through the air conditioner heat exchanger at low en‐
gine speeds and thus improves heat output.
♦ The supplementary heater control unit -J364- switches on the
circulation pump -V55- for example if it receives the following
information via the convenience data bus system (⇒ Auxiliary/
supplementary heater; Rep. gr. 82 and ⇒ "Guided fault-find‐
Audi A8 2003 ➤
Air conditioning - Edition 09.2010
4 Rep. gr.87 - Air conditioning system