Page 9 of 47

01-121
 
VAG1598/12 adapter cable Measuring range: Voltage measurement (20 V)  
Test 
step  VAG1598 
socket  Test of  
Test 
conditions  
- additional 
steps  Specified values  
Corrective action  
1.4   13 and 
ground  Terminal 30 
at E87  
Ignition off - approx. battery voltage - Repair voltage supply using 
wiring diagram. 
1.5   7 and 
ground  Terminal 58 
at E87  Ignition on Parking 
lights on - approx. battery voltage - Repair voltage supply using 
wiring diagram. 
1.6   7 and 
ground  Terminal 58 
at E87  Ignition on Parking 
lights on - less than 2 V - Rectify short circuit to positive 
using wiring diagram. 
1.7   45 and 
ground  Terminal 58D 
at E87  Ignition on Parking 
lights on - 0 to 12 V (depends on 
setting of illumination 
rheostat) - Determine and rectify open circuit 
or short circuit using wiring 
diagram. 
1.8   45 and 
ground  Terminal 58D 
at E87  Ignition on Parking 
lights off - less than 2 V - Rectify short circuit to positive 
using wiring diagram. 
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        Page 28 of 47
01-137
 
Adapter cable VAG1598/11  
LED Voltage tester VAG1527B  
Test 
Step  VAG1598 
socket  Test of  
Test 
conditions  
- additional 
work  Specified Value  
Corrective action  
1.9   term.15 1) + 
33  Signal for time 
span ignition 
off  
Ignition 
on - LED lights up - Diagnose and repair short or open 
circuit in wiring/connections using wiring 
diagram. 
1.10   term.15 1) + 
33  Signal for time 
span ignition 
off  Ignition 
on 
 
 
 
- Start 
engine. - LED lights up
 
 
 
- LED flickers briefly 
(time signal) and then 
lights up again - Diagnose and repair short or open 
circuit in wiring/connections using wiring 
diagram. 
- Check signal from instrument cluster.
1) Terminal 15 (ignition) is available at -E87- connector -D-, terminal -9-.  
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        Page 31 of 47
01-140
 Test No. 3 (Fresh Air Blower -V2- and Control Module for Fresh Air Blower -J126-)  Adapter cable VAG1598/11  
Measuring range: Voltage measurement (20 V)  
Test Step  
VAG1598 socket  
Test of  
Test conditions  
- additional work  Specified Value  
Corrective action  
3.1 to 3.3    page 01
-124
   
Adapter cable VAG1598/11  
LED Voltage tester VAG1527B  
Test 
step  VAG1598 
socket  Test of  
Test 
conditions  
- additional 
work  Specified 
Value  Corrective action  
3.4   14 + 16   Control module for 
fresh air blower -
J126-  
Ignition 
on - LED lights up  - Diagnose and repair open circuit in 
wiring between -J126- and -E87- using 
wiring diagram. 
- Fresh Air Blower -V2- check for ease of 
movement. 
           
- Fresh air 
blower running. - Replace -J126-.
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        Page 35 of 47

01-143
 
A/C control head -E87- connected to test box with adapter cable VAG1598/11  
LED Voltage tester VAG1527B  
Test 
Step  VAG1598 
socket  Test of  
Test conditions  
- additional work  Specified 
Value  Corrective action  
5.8   14 + 12   "A/C compressor 
intervention" 
output.  
Engine 
running. A/C 
compressor 
off 
- Switch on A/C 
compressor - LED lights 
up 
 
 
- LED lights 
up slightly 
dimmer. - Diagnose and repair open or short circuit in 
wiring/connections using wiring diagram. 
- 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. 
5.9   Ground 
and 
51  "Engine 
temperature too 
high" signal.  Engine 
running. - LED lights 
up. - Diagnose and repair short circuit to ground 
in wiring/connections using wiring diagram. 
- Diagnose and eliminate A/C compressor 
cut-off condition from Instrument cluster 
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        Page 42 of 47

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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        Page 44 of 47

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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