air condition AUDI A4 1998 B5 / 1.G AC System On Board Diagnostic Workshop Manual

01-6
The following components previously monitored
by OBD and triggered by A/C control head -E87-
are deleted:

Refrigerant low pressure switch -F73-.
Refrigerant high pressure switch -F118- (low
and high pressure switch functions integrated
into A/C pressure switch, -F29-).
Fresh air/recirculating flap two-way valve -
N63-.
The following new components are monitored by
OBD and provide input signals to -E87-:
A/C pressure switch -F129-.
Sender for outlet temperature, center -G191-.
Sender for outlet temperature, floor outlet -
G192-.
The following components monitored by OBD or
triggered by -E87- are revised:
The heater/air conditioner assembly with all
servo motors.
Pa
ge 8 of 91 A/C s
ystem, On Board Dia
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)
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01-7

A/C system changes

Revised heating/air conditioner assembly with
flap motors page 87
-174
.

The air flow flap motor now activates the fresh
air/recirculating air flap as well.
The two way valve for the circulating/fresh air
door, the vacuum unit and the vacuum reservoir
are deleted.

A/C refrigerant circuit changes
New service valve connection on low pressure
side.
Service valve connection for high pressure side
installed in high pressure line in plenum panel
(deleted at condenser).
A/C pressure switch -F129- replaces pressure
switches -F73- and -F118-.
New version "Zexel" compressor and high
pressure line (4-cyl. engines only).
Pa
ge 10 of 91 A/C s
ystem, On Board Dia
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)
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01-21

Notes:

1997 If A/C control head -E87- is unable to
determine the duration of time when ignition is
off ("standing time"), DTC 01206 "signal for time
span ignition off" is loaded into memory. The
A/C control head will then default to a standing
time greater than 4 hours. The actual measured
values of the outside temperature sensor are
then used as instantaneous outside and engine
temperature inputs for A/C system control.
When the "heating" mode is selected under
these conditions, fresh air blower -V2- has a
delayed start (even when the actual standing
time is less than 4 hours and the engine is
warm) page 01
-86
, Read Measuring Value
Block. The outside air temperature display -
G106- may also indicate incorrect outside
temperature values.

If both display fields of the A/C control head do
not light with ignition switched on check control
head coding Page 01
-57
.
Pa
ge 27 of 91 A/C s
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)
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01-23
Notes

If 22 C (72 F) is always displayed after switching ignition off and on, regardless of last setting, check power supply
(terminal 30) to A/C control head -E87- using wiring diagram. If a malfunction is recognized at an air/temperature distribution flap motor potentiometer, air distribution can be altered by
pressing buttons on A/C control head -E87-.
To switch display from C (Celsius) to F (Fahrenheit)(and vice versa), press "Temperature +" button while holding
"recirculating air" button. If no DTC are displayed and air conditioning system complaints exist (e.g. compressor does not run or only occasionally,
system control unsatisfactory, speed of fresh air blower cannot be regulated etc.), perform function 03 "Output Diagnostic
Test Mode (DTM)" and 08 "Read Measuring Value block."
Pa
ge 30 of 91 A/C s
ystem, On Board Dia
gnostic
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)
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01-39

VAG1551 scan tool
display Possible cause
Corrective action
00792 3224
A/C Pressure Switch
-F129-

Short circuit to
ground /SP - Open circuit in wiring/connections between -F129-
and -E87-
- Malfunction in operation of coolant fan -V7- (stage 1)


- Condenser or radiator dirty.
- Malfunction in operation of coolant fan -V7- (stage 2)
by A/C pressure switch -F129-
- -F129- malfunction
- Excess or low refrigerant system pressure- Diagnose and repair short or open circuit
in wiring using wiring diagram.
- Test fan operation -V7- (stage 1) using
function 03 (Output DTM)
page 01
-42

- -V7- electrical test
page 01
-115
.
- Clean condenser and radiator.
- Test -V7- (stage 2) via A/C pressure
switch -F129- page 87
-67
).
- Test -F129- page 87
-67
.
- Check refrigerant system pressures
page 87
-192
.
Notes:

A/C pressure switch -F129- contains 2 switching elements. Via terminals 1 & 2, the compressor is shut off due to low or
excess refrigerant system pressure (switch open). Via terminals 3 & 4, the second speed coolant fan is switched on
(switch closed).
When -F129- terminals 1 & 2 open, excess refrigerant pressure is initially recognized by A/C control head -E87- and a
DTC is stored. If the measured outside temperature is between 0 C & 50 C (32 F & 122 F) and -F129- terminals 1 &
2 remain open for longer than 30 seconds, -E87- switches over from excess pressure to low pressure (Low pressure
switch function) page 01
-86
, Read measuring value block (Display group 01 compressor shut-off conditions).
Pa
ge 53 of 91 A/C s
ystem, On Board Dia
gnostic
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)
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01-40

VAG1551 scan tool
display Possible cause
Corrective action
01206
Signal for time span
ignition off1)

implausible
signal /SP - Short or open circuit in wiring/connections
between instrument cluster and -E87-
- Instrument cluster malfunctioning.- Diagnose and repair short or open circuit in
wiring using wiring diagram.
- Check signal from instrument cluster using
function 08, Read measuring value block
page 01
-86
.
01274 4131
Air Flow Flap Motor -
V71- 2)

blocked or no
current /SP - Short or open circuit in wiring/connections
between -V71- and -E87-.
- Air flap or fresh/recirculated air flap
binding/sticking
- -V71- malfunctioning.- Diagnose and repair short or open circuit in
wiring using wiring diagram.
- Check air flap or fresh/recirculated air flap for
ease of movement.
- Check -V71- using function 03, Output
Diagnostic Test Mode (DTM) page 01
-42
.
1) If A/C control head -E87- is unable to determine the duration of time when ignition is off ("standing time"), DTC 01206
"signal for time span ignition off" is loaded into memory. The A/C control head will then default to a standing time greater than
4 hours. The actual measured values of the outside temperature sensor are then used as instantaneous outside and engine
temperature inputs for A/C system control. When the "heating" mode is selected under these conditions, the fresh air blower -
V2- has a delayed start (even when the actual standing time is less than 4 hours and the engine is warm) page 01
-86
,
Read measuring value block. The outside air temperature display -G106- may also indicate incorrect outside temperature
values.
2) -V71- operates the air flow flap as well as the fresh/recirculated air flap.
Pa
ge 55 of 91 A/C s
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)
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2)A/C Clutch -N25- cannot be actuated during Output DTM when certain compressor cut-off conditions exist, page 01
-63
,
Read measuring value block.
Pa
ge 66 of 91 A/C s
ystem, On Board Dia
gnostic
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)
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pair&id=AUDI.B5.HA01.01.1