Audi 100 1991 Operating instructions

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Repair 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 ➤
Refrigerant R134a Servicing
Edition 01.2011
Service
Service Department. Technical Information

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List of Workshop Manual Repair GroupsList of Workshop Manual
Repair GroupsList of Workshop Manual Repair Groups
Repair Group
00 - General, Technical Data
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 © 2011 Audi AG, Ingolstadt D3E80064E3D

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permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
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Contents
00 - General, Technical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1 General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 A/C System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Laws and Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.3 A/C System Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.4 Refrigerant Circuit and Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2 Description and Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
2.1 Refrigerant Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
2.2 Switches and Sensors on Refrigerant Circuit and Connections . . . . . . . . . . . . . . . . . . . . 74
2.3 Electrical Components Not on Refrigerant Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
2.4 A/C Service Station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
3 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
3.1 Charging Refrigerant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
3.2 Refrigerant R134a Capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
3.3 Refrigerant Oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
3.4 Refrigerant Oil Capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
4 Diagnosis and Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
4.1 Pressure Gauge, Tests and Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
4.2 Leak Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
4.3 Refrigerant Circuit Concerns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
4.4 Pressures, Checking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
5 Removal and Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
5.1 Leaking or Damaged Components Except A/C Compressor, Accumulator or Receiver -
Circuit Empty of Refrigerant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
5.2 Leaking or Damaged Components Except A/C Compressor, Accumulator or Receiver -
Circuit Contains Refrigerant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
5.3 Compressor, Replacing Without Flushing Refrigerant Circuit . . . . . . . . . . . . . . . . . . . . . . 193
5.4 Compressor, Replacing Due to Leakage Or Internal Damage . . . . . . . . . . . . . . . . . . . . . . 194
5.5 Receiver or Accumulator and Restrictor, Replacing After Cleaning Refrigerant Circuit . . . . 195
5.6 Receiver or Accumulator, Replacing Without Flushing Refrigerant Circuit . . . . . . . . . . . . 196
5.7 Dryer Cartridge and Dryer Bag, Replacing Without Flushing Refrigerant Circuit . . . . . . . . 197
6 Special Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
6.1 Commercially Available Tools and Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
6.2 Improvised Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Refrigerant R134a Servicing - Edition 01.2011
Contents i

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Refrigerant R134a Servicing - Edition 01.2011
ii Contents

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00 – General, Technical Data
1 General Information
⇒ “1.1 A/C System“, page 1
⇒ “1.2 Laws and Regulations“, page 12
⇒ “1.3 A/C System Principles“, page 18
⇒ “1.4 Refrigerant Circuit and Components“, page 21
1.1 A/C System
⇒ “1.1.1 Refrigerant R134a“, page 1
⇒ “1.1.2 Refrigerant R134a Characteristics“, page 2
⇒ “1.1.3 Refrigerant R134a Vapor Pressure Table“, page 4
⇒ “1.1.4 Handling Refrigerant“, page 5
⇒ “1.1.5 Refrigerant Oil“, page 7
⇒ “1.1.6 Refrigerant Oil Characteristics“, page 7
⇒ “1.1.7 Safety Precautions“, page 8
⇒ “1.1.8 Safety Precautions for Working with Extraction and
Charging System“, page 9
⇒ “1.1.9 Handling Pressure Vessels“, page 9
⇒ “1.1.10 Service and Recycling Units“, page 10
⇒ “1.1.11 Vehicles with A/C Compressor Without A/C Clutch, Only
with A/C Compressor Regulator Valve“, page 10
⇒ “1.1.12 Repairing A/C System“, page 10
1.1.1 Refrigerant R134a
Vehicle air conditioning systems make use of the vaporization and
condensation process. In this case, one works with a substance
which boils easily, designated as refrigerant.
The refrigerant employed is tetrafluoroethane R134a, which boils
at - 26.5° C at a vapor pressure of 1 bar.
Refrigerant R134a Environmental Information
♦ R134a is a fluorocarbon and contains no chlorine.
♦ R134a has a shorter atmospheric life span than refrigerant
R12.
♦ R134a does not damage the ozone layer. The ozone depletion
potential is zero.
♦ The greenhouse potential of R134a (Global Warming Potential
= GWP) is approximately 1300 (the GWP of carbon dioxide =
1).
♦ The global warming effect of R134a is “ten“ times less than
that of refrigerant R12.
Vehicles manufactured after 1992 have air conditioning systems
that use refrigerant R134a. This refrigerant does not contain
chlorine and does not deplete the ozone layer.
Refrigerant R12 was used through 1992. Due to its chlorine
atoms, this CFC has a high potential for depleting the ozone layer
as well as a tendency to increase the greenhouse effect.
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Refrigerant R134a Servicing - Edition 01.2011
1. General Information 1

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Conversion programs are available for old existing systems filled
with the ozone-depleting substance R12. Refer to Repair manual
for air conditioners with refrigerant R12 (this repair manual is only
available in hard copy).
For environmental protection reasons, refrigerants must not be
released into the atmosphere. For laws and regulations, refer to
⇒ “1.2 Laws and Regulations“, page 12 .
Refrigerant R134a Physical Data
Chemical formula CH2F–CF3 or CF3–CH2F
Chemical designation Tetrafluoroethane
Boiling point at 1 bar -26.5 °C
Solidification point -101.6 ℃
Critical temperature 100.6 ℃
Critical pressure 40.56 bar (absolute)
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, for ex‐
ample, 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. Refer to
⇒ “1.1.3 Refrigerant R134a Vapor Pressure Table“, page 4 .
Note
Different types of refrigerant are never to be mixed. Only the re‐
frigerant designated for the corresponding A/C system may be
used.
1.1.2 Refrigerant R134a Characteristics
The vapor pressure curves of R134a and other refrigerants are
sometimes very similar, therefore it is not possible to make a cer‐
tain distinction solely by pressure.
With R134a, the A/C compressor is lubricated with special syn‐
thetic refrigerant oils, for example, PAG oils (polyalkylene glycol
oils).
Trade Names and Designations
Refrigerant R134a is currently available under the following trade
names:
♦ H-FKW 134a
♦ SUVA 134a
♦ KLEA 134a
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Refrigerant R134a Servicing - Edition 01.2011
2 Rep. Gr.00 - General, Technical Data

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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 designations Frigen and
Freon are trade names. They also apply to refrigerants which
may not be used in automotive vehicles.
Product Characteristics
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).
With regard to their physical properties, these are refrigerants
which have been liquefied 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.
Vapor 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 vapor particles condense. This state of equilibrium occurs
under the influence of pressure and is often called vapor pres‐
sure. Vapor pressure is a function of temperature. Refer to
⇒ “1.1.3 Refrigerant R134a Vapor Pressure Table“, page 4 .
Color
Like water, refrigerants are colorless in both vapor and liquid form.
Gas is invisible. Only the boundary layer between gas and liquid
is visible. (Liquid level in tube of charging cylinder or bubbles in
sight glass). Refrigerant R134a fluid may appear colored (milky)
in a sight glass. This cloudiness is caused by partially dissolved
refrigerant oil and does not indicate a malfunction.
Affect on Metal
In its pure state, refrigerant R134a is chemically stable and does
not corrode iron or aluminum.
Refrigerant impurities such as chlorine compounds however
cause corrosion of certain metals and plastics. This can lead to
blockage, leaks or deposits on the A/C compressor piston.
Critical Temperature/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").
Water Content
Only very small amounts of water are soluble in liquid refrigerant.
On the other hand, refrigerant vapor and water vapor 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 approximately 7g of water. This water flows as far as the nozzle
of the expansion valve or restrictor and turns to ice, the A/C sys‐
tem no longer has a cooling effect.
Water destroys the air conditioner as it combines with other im‐
purities at high pressures and temperatures to form acids.
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1. General Information 3

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Combustibility
Refrigerant is non-flammable. It actually has a fire-resistant or fire
extinguishing effect. Refrigerant decomposes when exposed to
flames or red-hot surfaces. UV light (occurring for example during
electric welding) also causes refrigerant decomposition. The re‐
sultant decomposition products are toxic and are not to be in‐
haled. However, irritation of the mucous membranes provides an
adequate and timely warning.
Charge Factor
A vessel must have space for vapor as well as liquid. As the tem‐
perature rises, the liquid expands. The vapor-filled space be‐
comes 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 forces that result are strong enough to rupture the vessel. To
prevent a vessel from being overfilled, the regulations regarding
compresses gasses specify how many kilograms of refrigerant
that may be added to a vessel per liter of interior volume. Multi‐
plying this filling factor with the interior volume gives the permitted
filling capacity. The figure for refrigerant used in vehicles is 1.15
kg / liter.
Leak Detection
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 leak detectors designed for the type of refrigerant. For ex‐
ample, a leak detector for R12 refrigerant will not work with R134a
because R134a refrigerant has no chlorine atoms so the leak de‐
tector will not respond to it.
1.1.3 Refrigerant R134a Vapor Pressure Ta‐
ble
The vapor pressure table for every refrigerant is published in lit‐
erature for refrigeration system engineers. This table makes it
possible to determine the vapor pressure acting on the column of
liquid in a vessel if the temperature of the vessel is known.
Because each refrigerant has its own characteristic vapor pres‐
sure table, refrigerant can be identified by measuring the pressure
and temperature.
Note
♦ At absolute pressure, 0 bar corresponds to absolute vacuum.
Normal ambient pressure (positive pressure) equals 1 bar ab‐
solute pressure. 0 bar pressure corresponds to an absolute
pressure of one bar on most pressure gauges (indicated by -1
bar below 0).
♦ Pressure is measured in different units: 1 MPa (mega Pascal)
corresponds to 10 bar positive pressure or 145 psi, 1 bar ab‐
solute pressure corresponds to 0 bar positive pressure and
thus to the ambient pressure (atmospheric pressure).
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Refrigerant R134a Servicing - Edition 01.2011
4 Rep. Gr.00 - General, Technical Data

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permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
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Temperature in °C Pressure in Bar (Positive Pres‐
sure) of 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
1.1.4 Handling Refrigerant
If refrigerant vessels are opened, the contents may escape in liq‐
uid or vapor form. This process is intensified the higher the
pressure in the vessel.
The pressure level is governed by two factors:
• The type of refrigerant in the vessel. The lower the boiling
point, the higher the pressure.
• The temperature level. The higher the temperature, the higher
the pressure.
WARNING
♦ There is a danger of ice-up.
♦ The refrigerant can then escape as a fluid or vapor.
♦ Do not open containers, which store refrigerant.
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1. General Information 5

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Protective Eyewear
Put on protective goggles. They prevent refrigerant getting into
the eyes, as this could cause severe injury from exposure to cold.
Protective Gloves and Clothing
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.
Fluid Refrigerant and Skin Precaution
The refrigerant draws heat for evaporation from the surrounding
area. Even if this is the skin. This may cause extremely low tem‐
peratures. Local frost bite may result (boiling point of R134a:
-26.5° C at ambient pressure).
Refrigerant Vapor Precaution
If highly concentrated refrigerant vapor escapes, it mixes with the
surrounding air and displaces the oxygen necessary for breath‐
ing.
Smoking Hazard
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 refrigerant decomposition due to the effect of heat
are not only toxic, but may also have a highly corrosive effect on
pipes and system components. They mainly take the form of hy‐
drogen fluoride.
Pungent Odor
A pungent odor indicates that the products of decomposition
mentioned above have already formed. Avoid inhaling these sub‐
stances under all circumstances, as otherwise the respiratory
system, 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 affected
clothing and rinse skin with copious amounts of water.
• Following inhalation of highly concentrated refrigerant vapors,
immediately take the affected person into the open air. Call a
doctor. Administer oxygen in the event of breathing difficulties.
If the affected person has difficulty breathing or cannot
breathe, tip head back and perform mouth to mouth respira‐
tion.
♦ Handling Pressure Vessels, refer to
⇒ “1.1.9 Handling Pressure Vessels“, page 9 .
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Refrigerant R134a Servicing - Edition 01.2011
6 Rep. Gr.00 - General, Technical Data