wiring diagram AUDI A4 1998 B5 / 1.G AC System Electrical Testing Owner's Manual

01-144

A/C control head -E87- connected to test box with adapter cable VAG1598/11
Measuring range: Current measurement (200 mA)
Test
Step VAG1598
socket Test of
Test conditions
- additional work Specified
Value Corrective action
5.10 Ground
and
12
"A/C compressor
intervention"
output.
Engine running. A/C compressor
off

- Switch on A/C
compressor



- Remove multimeter
connector probes
from test box - Less than 5
mA



- Less than
50 mA
- Compressor
does not en-
gage
- Compressor
engages
Repair Manual, Fuel Injection and
Ignition
Repair Manual, Automatic
Transmission - Diagnose and repair short circuit to
positive in wiring/connections using
wiring diagram.
- Replace A/C control head -E87-.



- Diagnose and eliminate A/C
compressor cut-off condition(s) from
Engine Control Module (ECM) or
Transmission Control Module (TCM)
- Diagnose and repair short circuit to
ground in wiring/connections using
wiring diagram.
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01-145

Adapter cable VAG1598/11 connected.
Measuring range: Resistance measurement (200 ) Test
Step VAG1598
socket Test of
Test
conditions
- additional
work Specified
Value Corrective action
5.11 2 + 42 A/C pressure switch -
F129- (between
terminals 1 and 2)
Ignition
off - Less than
20
- Diagnose and repair open circuit or contact
resistance in wiring/connections using wiring
diagram.1).
- Check A/C pressure switch -F129- page 87
-67
.
1) If compressor cut-off condition code 1, "A/C pressure switch -F129- open" etc. appears in read measuring value block,
display group 1, display field 1: - check for intermittent contact in wiring/connections to -F129- using wiring diagram - check
function of Coolant Fan -V7- stage 1 with Output DTM (function
03)
page 01
-42
- check A/C pressure switch -F129- function
(actuation of -V7- stage 2, terminals 3 and 4 page 87
-67
). If no fault is determined, check A/C refrigerant system pressures
page 87
-190
.
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01-147
Notes:
The following test steps are only performed for A/C control heads -E87- with two displays:

Teststep 2.2 (the instrument panel interior temperature sensor -G56- is installed in A/C control heads -E87- with one
display)
Test step 5.7 (the interior temperature sensor fan -V42- is installed in A/C control heads -E87- with one display)
Switch on test area at VAG1526 multimeter: voltage test (20 V =)

VAG1598/11 adapter cable connected
Test
step VAG1598A
socket Test of
Test
requirements
- additional
operations Specified
value Corrective action
1.15
4) 46 + Ground
3) Power supply
terminal 58 of A/C
control head -E87-
Ignition
switched on Park light
switched on

approx.
battery
voltage - Locate and repair open circuit or short
circuit to Ground in wiring connection to
A/C control head -E87- using wiring
diagram
1.16
4) 46 + Ground
3) Power supply
terminal 58 of A/C
control head -E87-
Ignition
switched on Park light
- Locate and repair open circuit or short
circuit to Ground in wiring connection to
A/C control head -E87- using wiring
diagram.
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01-148

Switch on test area at VAG1526 multimeter: voltage test (20 V)

VAG1598/12 adapter cable connected
Test
step VAG1598A
socket Test of
Test
requirements
- additional
operations Specified
value Corrective action
1.17
4) 8
+
14
Terminal 15 and Ground
connection at A/C control head
-E87- (power supply for A/C
clutch)
Ignition
switched on
approx.
battery
voltage - Repair power supply or
Ground connection
according to wiring
diagram
4) Only perform this test step for an A/C control head with one display.
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01-149

VAG1527 B Voltage Tester

A/C control head -E87- connected at test box (VAG1598/11 and /12 adapter cables)
VAG1598/11 adapter cable connected
Test
step VAG1598A
socket Test of
Test
requirements
- additional
operations Specified value
Corrective action
5.9 5) Ground
+
51 "Engine temperature
too high" signal
Engine
running
LED on
voltage tester
lights - Locate short circuit to Ground
and repair according wiring
diagram
- Eliminate A/C compressor cut-
off conditions in instrument
cluster
5) Only perform this test step for vehicles of m.y. 1997 or later
Notes:
Ignition key coding is transmitted to the A/C control head -E87- from the instrument cluster along with the coolant
temperature and the signal "engine temperature too high" when ignition is switched on for vehicles as of m.y. 1999 (data
message). Key coding can only be processed by A/C control heads -E87- with part number 8D0 820 043 after index "M."
No information can be transmitted if the coolant temperature is too high.
When ignition is switched on, A/C control head -E87- begins with the setting that was valid when the ignition was last
switched off with this key (temperature, air distribution, fresh air blower RPM).
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01-150
List of changes to electrical tests, 1998 VAG1527B voltage tester
VAG1598/11 adapter cable connected
Test
step VAG1598
sockets Test of
Test
conditions
- additional
operations Specified
value Corrective action
1.9 33 +
GND Signal for
"ignition off"
period
Ignition
switched on LED on voltage tester lights
- Repair open circuit or
short circuit according to
wiring diagram.
1.10 33 +
GND Signal for
"ignition off"
period Ignition
switched on
- Start engine.LED in voltage tester lights up
When starting engine, LED briefly
flickers in voltage tester (time signal)
and then lights constantly - Repair open circuit or
short circuit according to
wiring diagram.
- Check instrument cluster.
Note:
Test steps 1.9 and 1.10 apply only for vehicles beginning m.y. 1997 (A/C control head with Part No. 8L0 820 043 up to Part
No. index letter "C").
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01-151

Voltage test - switch multimeter to 20V measuring range
VAG1598/11 adapter cable connected
Test
step VAG1598
sockets Test of
Test conditions
- additional
operations Specified
value Corrective action
1.11 7 + GND Terminal 58s on -
E87-
Ignition switched
on Parking light
switched on 0 to 12 V
- Repair open circuit or short circuit
according to wiring diagram.
1.12 7+ GND Terminal 58s on -
E87- Ignition switched
on Parking light
switched off approx. 0
V. - Repair short to B+ according to wiring
diagram.
Notes:

Test steps 1.11 to 1.14 apply for vehicles beginning m.y. 1998 (A/C control head with Part No. 8L0 820 043 from Part No.
index letter "D").
The Ground connection can be made via connector D, terminals 14 and 15 (for example).
The voltage at terminal 58s is dependent on the adjustment of the illumination dimmer control.
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01-152

Voltage test - switch multimeter to 20V measuring range
VAG1598/11 adapter cable connected
Test
step VAG1598
sockets Test of
Test conditions
- additional
operations Specified
value Corrective action
1.13 45 +
GND Terminal 58d on -
E87-
Ignition switched
on Parking light
switched on 0 to12 V
- Repair open circuit or short circuit
according to wiring diagram.
1.14 45 +
GND Terminal 58d on -
E87- Ignition switched
on Parking light
switched off 0 to 12 V
- Repair open circuit or short circuit
according to wiring diagram.
Notes:

Test steps 1.11 - 1.14 apply for vehicles beginning m.y. 1998 (A/C control head with Part No 8L0 820 043 from Part No.
index letter "D").
The Ground connection can be made via connector D, terminals 14 and 15 (for example).
The voltage to terminal 58d is created as a square-wave signal from the instrument cluster. The brightness of the display
on A/C control head -E87- is determined by the period of activation. The multimeter will indicate the average value.
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