Audi TT 24 User Manual
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Service
Workshop Manual
Audi 100 1991 ➤ , Audi 80 1992 ➤ ,
Audi A1 2011 ➤ , Audi A2 2001 ➤ ,
Audi A3 1997 ➤ , Audi A3 2004 ➤ ,
Audi A4 1995 ➤ , Audi A4 2001 ➤ ,
Audi A4 2008 ➤ ,
Audi A4 Cabriolet 2003 ➤ ,
Audi A5 Cabriolet 2009 ➤ ,
Audi A5 Coupé 2008 ➤ ,
Audi A5 Sportback 2010 ➤ ,
Audi A6 1995 ➤ , Audi A6 1998 ➤ ,
Audi A6 2005 ➤ , Audi A6 2011 ➤ ,
Audi A7 Sportback 2011 ➤ ,
Audi A8 1994 ➤ , Audi A8 2003 ➤ ,
Audi A8 2010 ➤ , Audi Cabriolet 1991 ➤ ,
Audi Q5 2008 ➤ , Audi Q7 2007 ➤ ,
Audi R8 2007 ➤ , Audi TT 1999 ➤ ,
Audi TT 2007 ➤
Air conditioner with refrigerant R134a
Edition 01.2011
Service Department. Technical Information
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Service
List of Workshop Manual Repair GroupsList of Workshop Manual
Repair GroupsList of Workshop Manual Repair Groups
Re pa ir G ro up
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.
All rights reserved.
No reproduction without prior agreement from publisher.
Copyright © 2011 Audi AG, Ingolstadt A0053300220
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.
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Air conditioner with refrigerant R134a - Edition 01.2011
Contents
87 - Air conditioning system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1 General information on air conditioning systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.3 Safety precautions for vehicles with a start/stop system . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.4 Other reference material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.5 Basics of air conditioning technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.6 Refrigerant R134a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.7 Properties of refrigerant R134a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.8 Refrigerant oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.9 How air conditioning works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.10 General work safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.11 Product properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.12 Handling refrigerant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.13 Handling pressure vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.14 Safety regulations for working with extraction and charging systems . . . . . . . . . . . . . . . . 13
1.15 Safety measures when working on vehicles with air conditioning and when working with
refrigerant R134a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.16 Basics for working on refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.17 Before starting up air conditioning system after fresh charging . . . . . . . . . . . . . . . . . . . . . . 17
2 General information on refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.1 Refrigerant circuit components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.2 Arrangement of the refrigerant circuit components and their influence on the high and low-
pressure ends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.3 Design of refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.4 Quick-release coupling connections in refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.5 Switches and senders in refrigerant circuit and related connections . . . . . . . . . . . . . . . . . . 31
2.6 Electrical components not installed in refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.7 Pressures and temperatures in refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.8 Test and measurement operations which can be performed with a pressure gauge . . . . 40
2.9 Air conditioner service and recycling units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
2.10 Repair information for refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3 Laws and regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.1 Laws and regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4 Refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.1 Important repair information for air conditioning systems . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.2 Converting refrigerant circuits from R12 refrigerant to R134a . . . . . . . . . . . . . . . . . . . . . . 48
4.3 Working with the air conditioner service station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.4 Blowing out refrigerant circuit with compressed air and nitrogen . . . . . . . . . . . . . . . . . . . . 60
4.5 Flushing (cleaning) refrigerant circuit with refrigerant R134a . . . . . . . . . . . . . . . . . . . . . . . . 64
4.6 Determining refrigerant circuit leaks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5 Problems with refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.1 Possible problems with refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
6 Connecting air conditioner service station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
6.1 Connecting air conditioner service station on vehicles with a connection on the low and high-
pressure end of the refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
6.2 Connecting air conditioner service station on vehicles with no connection on the low-pressure
end of the refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
7 Checking pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
7.1 Checking pressures in refrigerant circuit (with air conditioner service station) with ignition
switched off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
7.2 Checking pressures on vehicles with a restrictor and reservoir (with internally regulated air
conditioner compressor) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Contents i
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Air conditioner with refrigerant R134a - Edition 01.2011
7.3 Checking pressures on vehicles with an expansion valve and receiver (with internally
regulated air conditioner compressor) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
7.4 Checking pressures on vehicles with restrictor, reservoir and air conditioner compressor
regulating valve N280 (with externally regulated air conditioner compressor) . . . . . . . . . . 125
7.5 Checking pressures on vehicles with expansion valve, receiver and air conditioner
compressor regulating valve N280 (with externally regulated air conditioner compressor)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
8 Replacing components of refrigerant circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
8.1 Replacing components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
9 Capacities for refrigerant R134a, refrigerant oil and approved refrigerant oils . . . . . . . . . . 152
9.1 Capacities for refrigerant R134a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
9.2 Approved refrigerant oils and refrigerant oil capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
10 Test equipment and tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
10.1 List of testers, tools and materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
10.2 Tools and materials available from regional sales centre or importer . . . . . . . . . . . . . . . . 201
10.3 Commercially available tools and materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
10.4 Improvised tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
ii Contents
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Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Air conditioner with refrigerant R134a - Edition 01.2011
87 – Air conditioning system
1 General information on air condition‐
ing systems
1.1 General information
♦ Introduction ⇒ page 1
♦ Other reference material ⇒ page 2
♦ Basics of air conditioning technology ⇒ page 3
♦ Refrigerant R134a ⇒ page 5
♦ Properties of refrigerant R134a ⇒ page 6
♦ Refrigerant oil ⇒ page 9
♦ How air conditioning works ⇒ page 10
♦ General work safety ⇒ page 11
♦ Product properties ⇒ page 11
♦ Handling refrigerant ⇒ page 11
♦ Handling pressure vessels ⇒ page 13
♦ Safety regulations for working with extraction and charging
systems ⇒ page 13
♦ Safety measures when working on vehicles with air condition‐
ing and when working with refrigerant R134a ⇒ page 14
♦ Basics for working on refrigerant circuit ⇒ page 15
♦ Before starting up air conditioning system after fresh charging
⇒ page 17
1.2 Introduction
The purpose of this publication is to provide foremen and me‐
chanics with basic knowledge so that they can work in an expert
manner.
Note
This requires careful study of the manual, coupled with suitable
training on automotive air conditioning systems (with a qualifica‐
tion test if applicable) and the ability to apply the acquired exper‐
tise in practice.
This document is a compact reference work which should be kept
at the workplace. It should also be kept available for presentation
to the responsible supervisory agency upon request.
1. General information on air conditioning systems 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.
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Air conditioner with refrigerant R134a - Edition 01.2011
Vehicles with start/stop system
WARNING
Risk of injury due to automatic starting of engine on vehicles
with a start/stop system.
♦ The engine may start automatically if required on vehicles
with an activated start/stop system (indicated in the dash
panel insert).
♦ When working on the vehicle it should thus be ensured
that the start/stop system has been deactivated (switch off
ignition, switch on again if necessary).
All vehicles
Caution
Non-approved tools or materials (e.g. sealing additives) may
damage/impair the system.
Use is only to be made of tools and materials approved by the
manufacturer.
Warranty claims will be invalidated by the use of non-approved
tools or materials.
1.3 Safety precautions for vehicles with a start/stop system
WARNING
Risk of injury due to automatic starting of engine on vehicles
with a start/stop system.
♦ The engine may start automatically if required on vehicles
with an activated start/stop system (indicated in the dash
panel insert).
♦ When working on the vehicle it should thus be ensured
that the start/stop system has been deactivated (switch off
ignition, switch on again if necessary).
1.4 Other reference material
♦ Workshop manual for model-specific servicing work ⇒ Heat‐
ing, air conditioning; Rep. gr. 87 or ⇒ Air conditioning; Rep.
gr. 87 (vehicle-specific workshop manual) and ⇒ Current flow
diagrams, Electrical fault finding and Fitting locations
♦ Technical Service Handbook outlining action to be taken to
rectify current problems
♦ Self-study programmes, e.g. ⇒ Self-study programme No.
208 ; Air conditioning systems in motor vehicles
♦ Video programmes for in-dealership training
♦ List of special tools and workshop equipment required for
servicing air conditioning systems ⇒ Workshop equipment
catalogue
♦ Service Organisation Handbook Vol. „1“ „Additional equip‐
ment“ ⇒ Audi-ServiceNet, Handbooks
2 Rep. gr.87 - Air conditioning system
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Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Air conditioner with refrigerant R134a - Edition 01.2011
♦ Air conditioner with refrigerant R12 Workshop Manual (for ve‐
hicles manufactured up to model year 1993; this Workshop
Manual is available in hardcopy form only)
1.5 Basics of air conditioning technology
♦ Physical principles ⇒ page 3
♦ Pressure and boiling point ⇒ page 3
♦ Vapour pressure table for refrigerant R134a ⇒ page 4
♦ Properties of refrigerant R134a ⇒ page 6
1.5.1 Physical principles:
The four familiar states of water apply to air conditioning refriger‐
ants as well.
1 - Gas (invisible)
2 - Vapour
3 - Liquid
4 - Solid
When water is heated in a vessel (heat absorption), water vapour
can be seen to rise. If the vapour is further heated through heat
absorption, the visible vapour turns into invisible gas. The process
is reversible. If heat is extracted from gaseous water -A-, it
changes first to vapour -B-, then to water and finally to ice.
A - Heat absorption
B - Heat emission
Heat always flows from a warmer to a colder substance
Every substance consists of a mass of moving molecules. The
fast moving molecules of a warmer substance give off some of
their energy to the cooler and thus slower molecules. As a result,
the molecular motion of the warmer substance slows down and
that of the colder substance is accelerated. This process contin‐
ues until the molecules of both substances are moving at the
same speed. They are then at the same temperature and no fur‐
ther heat exchange takes place.
1.5.2 Pressure and boiling point
The boiling point given in tables for a liquid is always referenced
to an atmospheric pressure of 1 bar. If the pressure acting on a
fluid changes, its boiling point also changes.
1. General information on air conditioning systems 3
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Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Air conditioner with refrigerant R134a - Edition 01.2011
Note
Pressure may be given in various units: 1 MPa (megapascal) cor‐
responds to 10 bar gauge pressure or 145 psi; 1 bar absolute
pressure corresponds to 0 bar gauge pressure, which is roughly
equivalent to atmospheric pressure.
For example, the lower the pressure, the lower the temperature
at which water boils.
The vapour pressure curves for water and refrigerant R134a show
for example that, at constant pressure, reducing the temperature
changes vapour to liquid (in the condenser) or that, for instance,
reducing pressure causes the refrigerant to change from the liquid
to the vapour state (in the evaporator).
Vapour pressure curve for water
A - Liquid
B - Gas
C - Vapour pressure curve for water
1 - Pressure acting on liquid in bar (absolute)
2 - Temperature in °C
Vapour pressure curve for refrigerant R134a
A - Liquid
B - Gas
D - Vapour pressure curve for refrigerant R134a
1 - Pressure acting on liquid in bar (absolute)
2 - Temperature in °C
1.5.3 Vapour pressure table for refrigerant R134a
The vapour pressure table for every refrigerant is published in
literature for refrigeration system engineers. This table makes it
possible to determine the vapour pressure acting on the column
of liquid in a vessel if the temperature of the vessel is known.
As there is a known characteristic vapour pressure table for every
refrigerant, the type of refrigerant can be identified by way of
pressure and temperature measurement.
4 Rep. gr.87 - Air conditioning system
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Air conditioner with refrigerant R134a - Edition 01.2011
Note
♦
At absolute pressure, „0 bar“ corresponds to an absolute vac‐
uum. Normal atmospheric pressure corresponds to „1 bar“
absolute pressure. On the scales of most pressure gauges, „0
bar“ corresponds to an absolute pressure of 1 bar (this is in‐
dicated by the value „-1 bar“ below „0“).
♦
Pressure may be given in various units: 1 MPa (megapascal)
corresponds to 10 bar gauge pressure or 145 psi; 1 bar ab‐
solute pressure corresponds to 0 bar gauge pressure, which
is roughly equivalent to atmospheric pressure.
Temperature in °C Pressure in bar R134a
-45 -0,61
-40 -0,49
-35 -0,34
-30 -0,16
-25 0,06
-20 0,32
-15 0,63
-10 1,00
-5 1,43
0 1,92
5 2,49
10 3,13
15 3,90
20 4,70
25 5,63
30 6,70
35 7,83
40 9,10
45 10,54
50 12,11
55 13,83
60 15,72
65 17,79
70 20,05
75 22,52
80 25,21
85 28,14
90 31,34
1.6 Refrigerant R134a
Vehicle air conditioning systems make use of the vaporisation and
condensation process. Use is made of a substance with a low
boiling point, referred to as refrigerant.
The refrigerant used is tetrafluoroethane R134a, which boils at
-26.5°C at a vapour pressure of „1 bar“.
♦ Physical data of refrigerant R134a ⇒ page 6
♦ Critical point ⇒ page 6
1. General information on air conditioning systems 5
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Air conditioner with refrigerant R134a - Edition 01.2011
♦ Environmental aspects of refrigerant R134a ⇒ page 6
1.6.1 Physical data of refrigerant R134a
Chemical formula CH2F–CF3 or CF3–CH2F
Chemical designation Tetrafluoroethane
Boiling point at 1 bar -26.5 °C
Solidification point -101.6 °C
Critical temperature 100.6 °C
Critical pressure 40.56 bar (absolute)
1.6.2 Critical point
The critical point (critical temperature and critical pressure) is that
above which there is no longer a boundary between liquid and
gas.
A substance above its critical point is always in the gaseous state.
At temperatures below the critical point, all types of refrigerant in
pressure vessels exhibit both a liquid and a gas phase, i.e. there
is a layer of gas above the liquid.
As long as both liquid and gas are present in the vessel, the pres‐
sure is governed by ambient temperature ⇒ page 4 „Vapour
pressure table“.
Note
Different types of refrigerant are never to be mixed. Exclusive use
is to be made of the refrigerant specified for the respective air
conditioning system.
1.6.3 Environmental aspects of refrigerant R134a
♦ R134a is a fluorocarbon and contains no chlorine.
♦ R134a has a shorter atmospheric lifespan than refrigerant
R12.
♦ R134a does not damage the ozone layer, the ozone depletion
potential is zero.
♦ The global warming potential (GWP) of R134a is 1300 (the
GWP of carbon dioxide = 1).
♦ The global warming effect of R134a is „10“ times less than that
of refrigerant R12.
1.7 Properties of refrigerant R134a
♦ Trade names and designations ⇒ page 7
♦ Colour ⇒ page 7
♦ Vapour pressure ⇒ page 7
♦ Physical properties of R134a ⇒ page 7
♦ Effects on metal ⇒ page 7
♦ Critical temperature / critical pressure ⇒ page 7
♦ Water content ⇒ page 8
♦ Combustibility ⇒ page 8
♦ Charge factor ⇒ page 8
6 Rep. gr.87 - Air conditioning system
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with respect to the correctness of information in this document. Copyright by AUDI AG.
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Air conditioner with refrigerant R134a - Edition 01.2011
♦ Detecting leaks ⇒ page 8
1.7.1 Trade names and designations
The refrigerant R134a is currently available under the following
trade names:
♦ H-FKW 134a
♦ SUVA 134a
♦ KLEA 134a
Note
♦
Different trade names may be used in other countries.
♦
Of the wide range of refrigerants available, this is the only one
which may be used for vehicles. The names Frigen and Freon
are trade names. They also apply to refrigerants which are not
to be used in vehicles.
1.7.2 Colour
Like water, refrigerants are colourless in both vapour and liquid
form. Gas is invisible. Only the boundary layer between gas and
liquid is visible (liquid level in indicator tube of charging cylinder
or bubbles in sight glass). Liquid refrigerant R134a may have a
coloured (milky) appearance in a sight glass. This cloudiness is
caused by partially dissolved refrigerant oil and does not indicate
a fault.
1.7.3 Vapour pressure
In a partially filled, closed vessel, the quantity of refrigerant evap‐
orating from the surface equals the quantity returning to the liquid
state as vapour particles condense. This state of equilibrium oc‐
curs under the influence of pressure and is often called vapour
pressure. Vapour pressure is a function of temperature
⇒ page 4 „Vapour pressure table“.
1.7.4 Physical properties of R134a
As the vapour pressure curves of R134a and other refrigerants
are often very similar, unequivocal identification cannot be made
simply on the basis of pressure.
When using R134a, the air conditioner compressor is lubricated
by means of special synthetic refrigerant oils, e.g. PAG oils (pol‐
yalkylene glycol oils).
1.7.5 Effects on metal
In its pure state, refrigerant R134a is chemically stable and does
not corrode iron or aluminium.
However, contamination of the refrigerant, e.g. with chlorine com‐
pounds, leads to the corrosion of certain metals and plastics. This
can result in blockage, leaks or deposits at the air conditioner
compressor piston.
1.7.6 Critical temperature / critical pressure
The refrigerant R134a remains chemically stable up to a gas
pressure of 39.5 bar (corresponding to a temperature of 101 °C).
Above this temperature, the refrigerant decomposes (refer to
"Combustibility").
1. General information on air conditioning systems 7
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1.7.7 Water content
Only very small amounts of water are soluble in liquid refrigerant.
On the other hand, refrigerant vapour and water vapour mix in
any ratio.
Any water in the refrigerant circuit will be entrained in droplet form
once the dryer in the receiver or reservoir has absorbed as little
as approx. 7 g of water. This water flows as far as the expansion
valve nozzle or the restrictor and turns to ice. The air conditioner
no longer provides any cooling effect.
Water destroys the air conditioner because at high pressures and
temperatures it combines with other impurities to form acids.
1.7.8 Combustibility
Refrigerant is non-flammable. In fact it has a fire-inhibiting or fireextinguishing effect. Refrigerant decomposes when exposed to
flames or red-hot surfaces. UV light (occurring for example during
electric welding) also causes refrigerant decomposition. Products
of such decomposition are poisonous and must not be inhaled.
However, these chemicals irritate the mucous membranes, giving
adequate warning of their presence.
1.7.9 Charge factor
A vessel must have space for vapour as well as liquid. As the
temperature rises, the liquid expands. The vapour-filled space
becomes smaller. At a certain point, there will only be liquid in the
vessel. Beyond this, even a slight increase in temperature causes
great pressure to build up in the vessel as the liquid attempts to
continue expanding despite the absence of the necessary space.
The resultant force is sufficient to rupture the vessel. To stop ves‐
sels being overfilled, regulations governing the storage of com‐
pressed gases specify the number of kilograms of refrigerant with
which a vessel may be filled per litre of internal vessel volume.
The product of multiplying this charge factor by the internal vol‐
ume of the vessel is the permissible capacity. The figure for the
refrigerant used in motor vehicles is 1.15 kg/litre.
1.7.10 Detecting leaks
External damage, for example, can cause a leak in the refrigerant
circuit. The small quantity of refrigerant escaping from minor leaks
can be detected for example using an electronic leak detector or
by introducing a leak detection additive into the refrigerant circuit.
Electronic leak detectors are capable of registering leaks with re‐
frigerant losses of less than 5 g per year.
Note
Use must be made for the various refrigerants of leak detectors
designed for the composition of the refrigerant concerned. For
example, a leak detector for R12 refrigerant is not appropriate for
R134a, as R134a refrigerant has no chlorine atoms and the leak
detector therefore does not respond.
8 Rep. gr.87 - Air conditioning system
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1.8 Refrigerant oil
Caution
♦ For handling of refrigerant oil, refer to ⇒ Audi-ServiceNet,
HSO Environmental Protection (or ⇒ Volkswagen-Serv‐
iceNet, Handbooks, Service Handbook; Environmental
Protection; Immission Protection ).
Refrigerant oil mixes with the refrigerant (about 20 - 40 %, de‐
pending on compressor type and amount of refrigerant) and
circulates constantly in the system, lubricating the moving parts.
Special synthetic refrigerant oils, e.g. polyalkylene glycol (PAG)
oil, are used in conjunction with R134a air conditioning systems.
This is necessary as mineral oil, for example, does not mix with
R134a. In addition, the materials of the R134a air conditioning
system could be corroded as a result of mixture flowing through
the refrigerant circuit under pressure at high temperatures or
breakdown of the lubricating film in the air conditioner compres‐
sor. The use of non-approved oils can lead to the failure of the air
conditioning system; exclusive use is therefore to be made of au‐
thorised oils.
⇒ Electronic parts catalogue
Type of oil for R134a in motor vehicles: PAG. (polyalkylene glycol)
Note
♦
Do not store refrigerant oils in open containers as they are
extremely hygroscopic (water-absorbing).
♦
Always keep oil container sealed.
♦
Do not re-use old refrigerant oil. It must be disposed of as used
oil of unknown origin ⇒ Audi-ServiceNet, HSO Environmental
Protection (or ⇒ Volkswagen-ServiceNet, Handbooks, Serv‐
ice Handbook; Environmental Protection; Immission Protec‐
tion ).
♦
Ester-based oils are only intended for use with large systems
(not for motor vehicle air conditioners).
♦ Properties of refrigerant oil ⇒ page 9
1.8.1 Properties of refrigerant oil
The most important properties are a high degree of solubility with
refrigerant, good lubricity, absence of acid and minimal water
content. It is therefore only permissible to use certain specified
oils. For a list of approved refrigerant oils and capacities, refer to
⇒ page 174 .
PAG oils, which are appropriate for refrigerant R134a, are highly
hygroscopic and do not mix with other oils. Opened containers
should therefore be closed again immediately to prevent ingress
of moisture. Moisture and acids promote the ageing of refrigerant
oil, causing it to become dark, viscous and corrosive towards
metals.
1. General information on air conditioning systems 9
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Note
♦
On account of its chemical properties, the refrigerant oil is not
to be disposed of together with engine or gear oil. Refrigerant
oil must be disposed of as used oil of unknown origin ⇒ AudiServiceNet, HSO Environmental Protection (or ⇒ Volkswa‐
gen-ServiceNet, Handbooks, Service Handbook; Environ‐
mental Protection; Immission Protection ).
♦
Only oil approved for the air conditioner compressor is to be
used for refrigerant circuits containing refrigerant R134a ⇒
Electronic parts catalogue and capacities ⇒ page 174 .
1.9 How air conditioning works
The temperature in the passenger compartment depends on the
amount of heat radiated through the windows and conducted by
the metal parts of the body. In hot weather some of the heat must
be pumped off to achieve a more comfortable temperature for the
occupants.
As heat spreads into cooler areas, the passenger compartment
is fitted with a unit for generating low temperatures in which re‐
frigerant is constantly evaporated. The heat required for this is
extracted from the air flowing through the evaporator.
After absorbing heat, the refrigerant is pumped off through the air
conditioner compressor. The work of compression of the air con‐
ditioner compressor increases the heat content and temperature
of the refrigerant. Its temperature is now substantially higher than
that of the surrounding air.
The hot refrigerant flows with its heat content to the condenser,
where the refrigerant dissipates its heat to the surrounding air via
the condenser due to the temperature gradient between the re‐
frigerant and the surrounding air.
The refrigerant thus acts as a heat transfer medium. As it is reused, the refrigerant is returned to the evaporator.
For this reason all air conditioning systems are based on the re‐
frigerant circulation principle. There are however differences in
the composition of the units.
♦ Comfort ⇒ page 10
♦ Environmental aspects ⇒ page 11
1.9.1 Comfort
A basic requirement for concentrated and safe driving is a feeling
of comfort in the passenger compartment. Especially when it is
hot and humid, comfort can only be attained through the use of
air conditioning. Comfort can of course also be enhanced by
opening windows/the sun roof or increasing the air output. Such
a course of action is however associated with certain drawbacks
for the occupants of the vehicle, e.g. more noise, draughts, ex‐
haust fumes and unfiltered pollen (unpleasant for allergy suffer‐
ers).
Climate control together with a good heating and ventilation sys‐
tem concept can create a sense of wellbeing and comfort by
regulating the temperature, humidity and air circulation in the
passenger compartment to suit ambient conditions, with the ve‐
hicle both stationary and moving.
Other important advantages of air conditioning are:
10 Rep. gr.87 - Air conditioning system
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♦ Purification of the air supplied to the passenger compartment
(dust and pollen, for example, are washed out by the moist fins
of the evaporator and removed with the condensate).
♦ Temperatures in a mid-size car (example: after short travelling
time, ambient temperature 30 °C in the shade and vehicle ex‐
posed to sunlight).
With air conditioning Without air condi‐
tioning
At head height 23 °C 42 °C
At chest level 24 °C 40 °C
In footwell 30 °C 35 °C
1.9.2 Environmental aspects
As of around 1992, the air conditioning systems of newly manu‐
factured cars have been successively changed to refrigerant
R134a. This refrigerant contains no chlorine and therefore does
not deplete the ozone layer.
Until about 1992, the air conditioning systems were equipped with
refrigerant R12. Due to its chlorine atoms, this CFC had a high
ozone depletion potential as well as potential for intensifying the
greenhouse effect.
Conversion programmes are available for old existing systems
filled with the ozone-depleting substance R12 ⇒ Workshop Man‐
ual for air conditioners with refrigerant R12 (this Workshop Man‐
ual is available in hardcopy form only).
For environmental protection reasons, refrigerants must not be
released into the atmosphere ⇒ page 43 (laws and regulations).
1.10 General work safety
♦ As per VBG 20, German industrial liability insurance associa‐
tion (other regulations may apply in other countries)
♦ Heed the workplace-specific instructions ⇒ Audi-ServiceNet,
HSO Environmental Protection , which are to be displayed at
refrigerant workplaces.
1.11 Product properties
Refrigerants used in motor vehicle air conditioning systems be‐
long to the new generation of refrigerants based on chlorine-free,
partially fluorinated hydrocarbons (H-FKW, R134a; other names
may be used in other countries).
With regard to their physical properties, these are refrigerants
which have been liquified under pressure. They are subject to the
regulations governing pressure vessels and use is only to be
made of approved and appropriately marked containers.
Compliance with specific conditions is required to ensure safe and
proper use.
1.12 Handling refrigerant
If refrigerant vessels are opened, the contents may escape in liq‐
uid or vapour form. The higher the pressure in the vessel, the
more vigorous the process.
How high the pressure is depends on two factors:
• The type of refrigerant in the vessel. „Rule: The lower the boil‐
ing point, the higher the pressure.“
• The temperature „Rule: The higher the temperature, the high‐
er the pressure.“
1. General information on air conditioning systems 11
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WARNING
♦ There is a risk of icing-up.
♦ The refrigerant may emerge in liquid or vapour form.
♦ Do not open vessels containing refrigerant.
Wear safety goggles
Put on safety goggles to prevent refrigerant getting into the eyes,
as this could cause severe injury through frostbite.
Wear protective gloves and an apron
Greases and oils dissolve readily in refrigerants. They would
therefore destroy the protective layer of grease if allowed to come
into contact with the skin. Degreased skin is however sensitive to
the cold and germs.
Do not allow liquid refrigerant to come into contact with the skin
The refrigerant draws heat for evaporation from the surrounding
area - even if this is the skin. This may give rise to extremely low
temperatures and result in local frostbite (boiling point of R134a:
-26.5 °C at ambient pressure).
Do not inhale refrigerant vapours
If highly concentrated refrigerant vapour escapes, it mixes with
the surrounding air and displaces the oxygen necessary for
breathing.
Smoking is absolutely prohibited
A burning cigarette can cause refrigerant to decompose. The re‐
sultant substances are toxic and must not be inhaled.
Welding and soldering on refrigeration systems
Before performing welding or soldering work on vehicles in the
vicinity of air conditioning system components, extract refrigerant
and remove remnants by blowing out with nitrogen.
The products of decomposition of the refrigerant arising from the
effect of heat are not only toxic, but also highly corrosive and can
therefore damage pipes and sections of the system. The principal
substance is hydrogen fluoride.
Pungent odour
A pungent odour indicates that the products of decomposition
mentioned above are already present. Avoid inhaling these sub‐
stances under all circumstances, as otherwise the airways, lungs
and other organs could be damaged.
First aid
• Following contact with eyes or mucous membranes, immedi‐
ately rinse with copious amounts of running water and consult
an eye specialist.
• Following contact with the skin, immediately remove clothing
affected and rinse skin with copious amounts of water.
• Following inhalation of highly concentrated refrigerant va‐
pours, the person concerned is to be taken immediately into
the open air. Call a doctor. Administer oxygen in the event of
breathing difficulties. If the person affected is having great dif‐
ficulty breathing or is not breathing at all, tilt back the head and
administer artificial respiration.
♦ Handling pressure vessels ⇒ page 13
12 Rep. gr.87 - Air conditioning system
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1.13 Handling pressure vessels
Secure vessels to prevent them falling over.
Secure upright cylinders to stop them falling over and cylinders
lying flat to stop them rolling away.
Vessels are never to be thrown.
If dropped, the vessels could be so severely deformed that they
rupture. The refrigerant evaporates immediately, liberating con‐
siderable force. Flying fragments of cylinders can cause severe
injuries.
To protect the cylinder valves, cylinders are only to be transported
with the protective cap screwed on.
Cylinder valves may break off if not properly transported.
Never store in the vicinity of radiators,
as high temperatures may occur in these areas. High tempera‐
tures are also accompanied by high pressures and the maximum
permissible vessel pressure may be exceeded.
Never heat to above 50 °C
To avoid possible risk, pressure vessel regulations specify that
vessels are not to be heated to in excess of 50 °C.
Do not heat in an uncontrolled manner
Do not heat with a naked flame under any circumstances. Local‐
ised overheating can cause structural changes in the vessel
material, which then reduce its ability to withstand pressure.
There is also a danger of the refrigerant decomposing due to lo‐
calised overheating.
Seal empty vessels
Empty refrigerant containers must always be closed to prevent
the penetration of moisture. Moisture causes steel containers to
rust. Rust weakens the container walls. In addition, rust particles
which ingress into refrigeration systems from containers cause
malfunctions.
1.14 Safety regulations for working with ex‐
traction and charging systems
• Before connecting the charging system to the air conditioning
system, ensure that the shut-off valves are closed.
• Before disconnecting the charging system from the air condi‐
tioning system, ensure that the process has been completed
so that no refrigerant can escape into the atmosphere.
• Once the purified refrigerant from the charging system has
been filled into an external compressed-gas cylinder, close the
hand shut-off valves at the cylinder and charging system.
• Do not expose the charging system to moisture or use it in a
wet environment.
• Before performing service work on the charging system, dis‐
connect the power supply.
• To reduce the danger of fire, avoid using an extension cable.
If the use of an extension cable is unavoidable, the minimum
cross-section should be 2.5 mm2.
• In case of fire, remove the external cylinder.
• Entrained oil from the air conditioning system drawn off by the
suction unit into the measurement vessel supplied is subse‐
quently to be transferred to a sealable container, as it contains
1. General information on air conditioning systems 13
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a small quantity of refrigerant which must not be released into
the environment.
• Following shutdown, the air conditioner service station is to be
secured to stop it rolling away.
1.15 Safety measures when working on ve‐
hicles with air conditioning and when
working with refrigerant R134a
Vehicles with start/stop system
WARNING
Risk of injury due to automatic starting of engine on vehicles
with a start/stop system.
♦ The engine may start automatically if required on vehicles
with an activated start/stop system (indicated in the dash
panel insert).
♦ When working on the vehicle it should thus be ensured
that the start/stop system has been deactivated (switch off
ignition, switch on again if necessary).
All vehicles
WARNING
♦ It is advisable to always 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 administer eye drops and consult a doctor immedi‐
ately even if no pain is felt.
♦ The doctor must be informed that the frostbite was caused
by refrigerant R134a. Should refrigerant come into contact
with other parts of the body despite compliance with the
safety regulations, these must likewise be rinsed immedi‐
ately for approximately 15 minutes with cold water.
♦ Work may only be performed on the refrigerant circuit of
an air conditioning system in well ventilated areas. Work‐
shop extraction systems are to be switched on.
♦ Refrigerant must not be stored in low-level areas (e.g. cel‐
lars) and their exits or light wells.
• Welding, brazing and soldering operations are not to be per‐
formed on air conditioner components when filled. This also
applies to vehicle welding and soldering work if there is a dan‐
ger of air conditioner components becoming hot. When per‐
forming paintwork repairs, the temperature in the drying booth
or preheating zone must not exceed 80 °C.
Reason:
Exposure to heat gives rise to considerable pressure in the sys‐
tem, which could cause the pressure relief valve to open.
Remedy:
– Discharge refrigerant circuit with air conditioner service sta‐
tion.
14 Rep. gr.87 - Air conditioning system
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Note
Damaged or leaking components of the air conditioning system
are not to be repaired by welding or soldering. They must always
be replaced.
Refrigerant vessels (e.g. charging cylinders of air conditioner
service station) must never be subjected to excessive heat or ex‐
posed to direct sunlight.
Remedy:
– Vessels must never be completely filled with liquid refrigerant.
Without sufficient room for expansion (gas cushion), vessels
will rupture with devastating effect in the event of an increase
in temperature ⇒ page 6 .
Refrigerant should never be poured into systems or vessels con‐
taining any air.
Remedy:
– Evacuate systems and containers before charging with refrig‐
erant.
1.16 Basics for working on refrigerant circuit
Vehicles with start/stop system
WARNING
Risk of injury due to automatic starting of engine on vehicles
with a start/stop system.
♦ The engine may start automatically if required on vehicles
with an activated start/stop system (indicated in the dash
panel insert).
♦ When working on the vehicle it should thus be ensured
that the start/stop system has been deactivated (switch off
ignition, switch on again if necessary).
All vehicles
♦ General ⇒ page 15
♦ Cleaning refrigerant circuit ⇒ page 16 .
♦ Additionally for vehicles with air conditioner compressor with
no magnetic clutch (with air conditioner compressor regulating
valve -N280- ) ⇒ page 16
♦ O-rings ⇒ page 16
1.16.1 General
• Heed the workplace-specific instructions ⇒ Audi-ServiceNet,
HSO Environmental Protection .
• Ensure absolute cleanliness when working.
• Wear safety goggles and gloves when working with refrigerant
and nitrogen.
• Workshop extraction systems are to be switched on.
• Always use air conditioner service station to discharge refrig‐
erant circuit, then unfasten screw connections and replace
defective components.
1. General information on air conditioning systems 15
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• Use caps to seal off opened assemblies and hoses to prevent
the ingress of moisture and dirt.
• Make exclusive use of tools and materials intended for refrig‐
erant R134a.
• Seal opened refrigerant oil containers to protect against mois‐
ture.
Note
♦
After completing service work, screw sealing caps (with seals)
onto all connections with valves and service connections.
♦
Before starting up the air conditioning system, heed the vehi‐
cle-specific capacities ⇒ page 152 .
♦
Do not top up the refrigerant in the circuit; discharge the ex‐
isting refrigerant and re-charge the system.
1.16.2 Cleaning refrigerant circuit
Flush the refrigerant circuit with refrigerant R134a ⇒ page 64
(or blow out with compressed air and nitrogen ⇒ page 60 ) in
the following cases:
– If moisture or dirt has ingressed into the refrigerant circuit (e.g.
following an accident).
– If the refrigerant oil is dark and viscous.
– If there is too much refrigerant oil in the refrigerant circuit after
compressor replacement.
– If the air conditioner compressor has to be replaced on ac‐
count of „internal“ damage (e.g. noise or no output).
Note
When flushing components with compressed air and nitrogen, al‐
ways extract the gas mixture escaping from the components with
suitable extraction units (workshop extraction system).
1.16.3 Additionally for vehicles with air condi‐
tioner compressor with no magnetic
clutch (with air conditioner compressor
regulating valve -N280- only)
• The engine is only to be started following complete assembly
of the refrigerant circuit (constant air conditioner compressor
operation).
• If the engine has to be operated with the refrigerant circuit
empty, only do so for as long as absolutely essential and avoid
high engine speeds.
1.16.4 O-rings
♦ Make exclusive use of seals which are resistant to refrigerant
R134a and the related refrigerant oils. Colour coding of the Oring seals is no longer employed. Black and coloured O-rings
are used.
♦ Pay attention to the correct inside diameter of the seals used
⇒ Electronic parts catalogue , ⇒ Heating, air conditioning;
Rep. gr. 87 and / or ⇒ Air conditioning; Rep. gr. 87 (vehiclespecific workshop manual).
16 Rep. gr.87 - Air conditioning system
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♦ Seals are only to be used once.
♦ Before fitting, moisten seals slightly with refrigerant oil (PAG
oil).
1.17 Before starting up air conditioning sys‐
tem after fresh charging
– Give the air conditioner compressor approx. 10 turns by hand
by way of the magnetic clutch plate or the pulley.
– Start the engine with the air conditioning system switched off
( air conditioning system magnetic clutch -N25- and air condi‐
tioner compressor regulating valve -N280- are not actuated).
– Switch on the air conditioner compressor once the idling speed
has stabilised and run it for at least 10 minutes at idle in the
maximum cooling output setting.
1. General information on air conditioning systems 17
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2 General information on refrigerant
circuit
Vehicles with start/stop system
WARNING
Risk of injury due to automatic starting of engine on vehicles
with a start/stop system.
♦ The engine may start automatically if required on vehicles
with an activated start/stop system (indicated in the dash
panel insert).
♦ When working on the vehicle it should thus be ensured
that the start/stop system has been deactivated (switch off
ignition, switch on again if necessary).
All vehicles
♦ Refrigerant circuit components ⇒ page 18
♦ Arrangement of the refrigerant circuit components and their
influence on the high and low-pressure ends ⇒ page 19
♦ Design of refrigerant circuit ⇒ page 28
♦ Quick-release coupling connections in refrigerant circuit
⇒ page 29
♦ Switches and senders in refrigerant circuit and related con‐
nections ⇒ page 31
♦ Electrical components not fitted in the refrigerant circuit
⇒ page 35 .
♦ Pressures and temperatures in refrigerant circuit
⇒ page 36
♦ Test and measurement operations which can be performed
with a pressure gauge ⇒ page 40
♦ Air conditioner service and recycling units ⇒ page 41
♦ Repair information for refrigerant circuit ⇒ page 42
2.1 Refrigerant circuit components
• All components of the refrigerant circuit submitted for quality
observation are always to be sealed (use the original sealing
caps of the replacement part).
• Replace damaged or leaking components of the refrigerant
circuit ⇒ page 143 .
Note
The following replacement parts (air conditioner compressor, res‐
ervoir, evaporator and condenser) have so far been filled with
nitrogen gas. This charge is being gradually discontinued. Con‐
sequently, no or only very slight pressure equalisation is percep‐
tible on unscrewing the sealing plugs from the replacement part.
18 Rep. gr.87 - Air conditioning system
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2.2 Arrangement of the refrigerant circuit components and their influence on the high and low-pressure ends
High-pressure end: Condenser, receiver and restrictor or expan‐
sion valve to separate the high and low-pressure liquid ends.
High pressure results from the restrictor or expansion valve form‐
ing a constriction and causing the refrigerant to accumulate, thus
leading to an increase in pressure and temperature.
Excess pressure occurs if too much refrigerant or refrigerant oil
is used, the condenser is contaminated, the radiator fan is defec‐
tive, the system is blocked or in the event of moisture in the
refrigerant circuit (icing-up of restrictor or expansion valve).
Low-pressure end: Evaporator, evaporator temperature sensor
and air conditioner compressor to separate the high and lowpressure gas ends.
A drop in system pressure can be caused by a loss of refrigerant,
the restrictor or expansion valve (constrictions), a defective air
conditioner compressor or an iced-up evaporator.
♦ Air conditioner compressor ⇒ page 20
♦ Condenser ⇒ page 21
♦ Evaporator ⇒ page 22
♦ Reservoir ⇒ page 22
♦ Restrictor ⇒ page 23
♦ Receiver ⇒ page 24
♦ Expansion valve ⇒ page 25
♦ Refrigerant line with internal heat exchanger ⇒ page 25
♦ Refrigerant line quick-release coupling connections
⇒ page 26
♦ O-rings ⇒ page 27
♦ Pipes and hoses of refrigerant circuit ⇒ page 27
♦ Pressure relief valve ⇒ page 28
2. General information on refrigerant circuit 19
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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.
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Air conditioner with refrigerant R134a - Edition 01.2011
2.2.1 Air conditioner compressor
The air conditioner compressor is driven by the engine via a poly
V-belt or a drive shaft.
Air conditioner compressor with magnetic clutch:
♦ An electromagnetic clutch -A- attached to the air conditioner
compressor provides the power link between the pulley -Band the compressor crankshaft when the air conditioning sys‐
tem is switched on.
♦ An overload safeguard attached to the clutch plate or fitted in
the solenoid of the air conditioner compressor is triggered if
the air conditioner compressor is not running smoothly in order
to protect the belt drive against overload.
Air conditioner compressor with no magnetic clutch:
♦ An overload safeguard attached to the pulley -B- or fitted in
the drive unit of the air conditioner compressor is triggered if
the air conditioner compressor is not running smoothly in order
to protect the belt drive against overload.
All air conditioner compressors
The air conditioner compressor draws in refrigerant gas from the
evaporator, compresses it and conveys it to the condenser.
20 Rep. gr.87 - Air conditioning system
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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.
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Air conditioner with refrigerant R134a - Edition 01.2011
Note
♦
The air conditioner compressor contains refrigerant oil which
mixes with refrigerant R134a at all temperatures.
♦
The rating plate indicates the refrigerant for which the air con‐
ditioner compressor is designed. A valve regulates the pres‐
sure on the low-pressure end within the specified range
(control characteristic).
♦
At present, actuation is effected externally by way of a regu‐
lating valve -C- on air conditioner compressors with or without
magnetic clutch.
♦
On air conditioner compressors with no magnetic clutch, the
engine is only to be started following complete assembly of the
refrigerant circuit.
♦
To prevent air conditioner compressor damage if the refriger‐
ant circuit is empty, the magnetic clutch is deactivated and the
air conditioner compressor regulating valve -N280- no longer
actuated (air conditioner compressor idles with engine).
♦
If the refrigerant circuit is empty, an air conditioner compressor
with no air conditioning system magnetic clutch -N25- (with air
conditioner compressor regulating valve -N280- ) is switched
to internal lubrication by way of a valve.
♦
Depending on the version of the air conditioner compressor,
the high-pressure end of the air conditioner compressor may
be fitted with a valve to prevent the backflow of liquid refriger‐
ant into the compressor after switching off the air conditioning
system. If an air conditioner compressor with this valve is fitted
on a vehicle with a refrigerant circuit with an expansion valve,
a relatively long period may elapse before the pressure on the
high-pressure end decreases (the expansion valve is cold and
the pressure on the low-pressure end increases rapidly after
switch-off, the expansion valve closes and the refrigerant can
only flow slowly to the low-pressure end). If the air conditioner
compressor is switched on, the pressure on the low-pressure
end decreases, the expansion valve opens and the refrigerant
can flow to the low-pressure end.
♦
In the case of air conditioner compressors with an electro‐
magnetic clutch -A- and a regulating valve -C-, the electro‐
magnetic clutch -A- is usually only actuated when the
regulating valve -C- is actuated as well ⇒ Air conditioning;
Rep. gr. 87 .
2.2.2 Condenser
The condenser transfers heat from the compressed refrigerant
gas to the surrounding air.
In this process, the refrigerant gas condenses to form liquid.
Depending on the design of the refrigerant circuit, the receiver
may be attached to the condenser or installed in (integrated into)
the condenser ⇒ Heating, air conditioning; Rep. gr. 87 or ⇒ Air
conditioning; Rep. gr. 87 (vehicle-specific workshop manual) and
⇒ Electronic parts catalogue .
Note
2. General information on refrigerant circuit 21
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.
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Air conditioner with refrigerant R134a - Edition 01.2011
2.2.3 Evaporator
The liquid refrigerant evaporates in the tubes of the evaporator.
The required heat is extracted from the air flowing past the evap‐
orator ribs. The air cools down. The refrigerant evaporates and is
drawn in by the air conditioner compressor together with the heat
absorbed.
A restrictor or an expansion valve supplies a defined quantity of
refrigerant to the evaporator. In systems with an expansion valve
the flow rate is regulated such that only gaseous refrigerant
emerges at the evaporator outlet.
2.2.4 Reservoir
To ensure that the air conditioner compressor draws in only gas‐
eous refrigerant, the reservoir collects the mixture of vapour and
gas coming from the evaporator. The vapour becomes gaseous
refrigerant.
Refrigerant oil entrained in the circuit does not remain in the res‐
ervoir as an oil extraction hole is provided.
Any moisture ingressing into the refrigerant circuit during assem‐
bly is trapped by a filter (desiccant bag) in the reservoir.
Gaseous refrigerant with oil is drawn in by the air conditioner
compressor.
Note
♦
Replace the reservoir if the refrigerant circuit has been open
for a lengthy period and moisture has ingressed or if replace‐
ment is stipulated on the basis of a specific complaint
⇒ page 143 .
♦
Do not remove the sealing plugs -A- and -B- until immediately
prior to installation.
♦
If the reservoir is not sealed, the desiccant bag soon becomes
saturated with moisture and thus unusable.
♦
When installing, observe arrow indicating direction of flow if
applicable.
22 Rep. gr.87 - Air conditioning system
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.
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Air conditioner with refrigerant R134a - Edition 01.2011
2.2.5 Restrictor
The restrictor creates a constriction. This constriction restricts the
flow, thus separating the refrigerant circuit into a high and lowpressure end. Upstream of the restrictor, the refrigerant is warm
due to the high pressure. Downstream of the restrictor, the refrig‐
erant is cold due to the low pressure. Upstream of the narrow point
is a strainer to catch dirt and downstream of the narrow point is a
strainer to atomise the refrigerant before it enters the evaporator.
Note
♦
Arrow -A- on restrictor faces evaporator.
♦
Always replace after opening the circuit.
♦
Different versions exist; heed the applicable notes in the var‐
ious service information booklets ⇒ Heating, air conditioning;
Rep. gr. 87 or ⇒ Air conditioning; Rep. gr. 87 (vehicle-specific
workshop manual) and ⇒ Electronic parts catalogue .
2. General information on refrigerant circuit 23
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.
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Air conditioner with refrigerant R134a - Edition 01.2011
2.2.6 Receiver
The receiver collects the droplets of liquid and conveys them in a
continuous flow to the expansion valve. Any moisture ingressing
into the refrigerant circuit during assembly is collected by a dryer
in the receiver.
Note
♦
Replace the receiver if the refrigerant circuit has been open
for a lengthy period and moisture has ingressed or if replace‐
ment is stipulated on the basis of a specific complaint
⇒ page 143 .
♦
Do not remove the sealing plugs until immediately prior to in‐
stallation.
♦
If the receiver is not sealed, the desiccant bag soon becomes
saturated with moisture and thus unusable.
♦
When installing, observe arrow indicating direction of flow if
applicable.
♦
Depending on the design of the refrigerant circuit, the receiver
may also be attached to the condenser or installed in (inte‐
grated into) the condenser ⇒ Heating, air conditioning; Rep.
gr. 87 or ⇒ Air conditioning; Rep. gr. 87 (vehicle-specific
workshop manual) and ⇒ Electronic parts catalogue .
♦
The procedure for dealing with problems differs depending on
the version of the receiver / dryer cartridge. If, for example, the
receiver is attached to the condenser, it can be replaced to‐
gether with the dryer cartridge. If, for example, the receiver is
integrated into the condenser, it is usually possible to replace
the dryer cartridge and any additional filter element separately.
If the receiver is integrated into the condenser and it is not
possible to replace the receiver/dryer cartridge separately, it
may be necessary to replace the entire condenser ⇒ Heating,
air conditioning; Rep. gr. 87 or ⇒ Air conditioning; Rep. gr.
87 (vehicle-specific workshop manual) and ⇒ Electronic parts
catalogue .
♦
Depending on the design of the refrigerant circuit, the desic‐
cant bag (dryer cartridge) may also be installed in the con‐
denser ⇒ Heating, air conditioning; Rep. gr. 87 or ⇒ Air
conditioning; Rep. gr. 87 (vehicle-specific workshop manual)
and ⇒ Electronic parts catalogue .
24 Rep. gr.87 - Air conditioning system
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.
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Air conditioner with refrigerant R134a - Edition 01.2011
2.2.7 Expansion valve
The expansion valve atomises the refrigerant flowing in and con‐
trols the flow rate in line with the quantity of heat transferred such
that it does not become gaseous before reaching the evaporator
outlet.
Note
♦
Pay attention to the correct part number on replacing the ex‐
pansion valve. ⇒ Electronic parts catalogue
♦
Different characteristic curves matched to the appropriate cir‐
cuit ⇒ Heating, air conditioning; Rep. gr. 87 or ⇒ Air condi‐
tioning; Rep. gr. 87 (vehicle-specific workshop manual) and
⇒ Electronic parts catalogue .
♦
Depending on the version of the air conditioner compressor,
the high-pressure end of the air conditioner compressor may
be fitted with a valve to prevent the backflow of liquid refriger‐
ant into the compressor after switching off the air conditioning
system. If an air conditioner compressor with this valve is fitted
on a vehicle with a refrigerant circuit with an expansion valve,
a relatively long period may elapse before the pressure on the
high-pressure end decreases (the expansion valve is cold and
the pressure on the low-pressure end increases rapidly after
switch-off, the expansion valve closes and the refrigerant can
only flow slowly to the low-pressure end). If the air conditioner
compressor is switched on, the pressure on the low-pressure
end decreases, the expansion valve opens and the refrigerant
can flow to the low-pressure end.
2.2.8 Refrigerant line with internal heat ex‐
changer
In this refrigerant line, the hot liquid refrigerant flowing on the highpressure end supplies energy to the cold refrigerant gas or vapour
flowing on the low-pressure end, thus enhancing the efficiency of
the air conditioner.
Note
This illustration shows a refrigerant line with an internal heat ex‐
changer as fitted for example on the Audi A4 2008 > and the Audi
A5 Coupé 2008 > ⇒ Air conditioning; Rep. gr. 87 (vehicle-specific
workshop manual).
A - Refrigerant line with internal heat exchanger
B - Channels in the refrigerant line in which the hot liquid refrig‐
erant flows to the evaporator (high-pressure end of the refrigerant
circuit).
C - Channel in the refrigerant line in which the cold refrigerant gas
or vapour flows to the air conditioner compressor (low-pressure
end of the refrigerant circuit).
2. General information on refrigerant circuit 25
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.
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Air conditioner with refrigerant R134a - Edition 01.2011
2.2.9 Refrigerant line quick-release coupling connections
WARNING
The quick-release couplings are only to be released and un‐
fastened after draining the refrigerant circuit.
Note
♦
This illustration shows the quick-release couplings with a re‐
frigerant line with an internal heat exchanger as fitted for
example on the Audi A4 2008 > and the Audi A5 Coupé 2008
> ⇒ Air conditioning; Rep. gr. 87 (vehicle-specific workshop
manual).
♦
Removal of the refrigerant line -D- involves opening the re‐
taining ring -A- with the air conditioner line release tool T40149/- for example ⇒ Air conditioning; Rep. gr. 87 (vehiclespecific workshop manual).
♦
Following removal of the applicable refrigerant line, the quickrelease couplings -B- and -G- are to be replaced together with
the corresponding support ring -E- or -H- and the correspond‐
ing O-ring -F- or -J- ⇒ Air conditioning; Rep. gr. 87 (vehiclespecific workshop manual) and ⇒ Electronic parts catalogue .
A - Retaining ring (in quick-release coupling connection on highpressure end)
B - Quick-release coupling connection with retaining ring „highpressure end“
C - Refrigerant line with an internal heat exchanger
D - Refrigerant line „high-pressure end“
E - Support ring „high-pressure end“
F - O-ring „high-pressure end“
G - Quick-release coupling connection with retaining ring „lowpressure end“
H - Support ring „low-pressure end“
J - O-ring „low-pressure end“
26 Rep. gr.87 - Air conditioning system
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