Compressor relay: Diagnosis/troubleshooting

DIAGNOSIS/TROUBLESHOOTING PROCEDURE

Work instruction			Display OK	If not OK
1	Lower vehicle to low level or loaded level several times if necessary		→ End	Go to Step 2
2	Check fuse	Check 1a Switch off ignition. Remove fuse 'F13' (40A) from fuse carrier in back-up fuse box and check for continuity.	Go to Step 5	Go to Step 3
2	Check fuse	Check 1b Re-insert intact fuse 'F13' (40A). Measure voltage at output of fuse 'F13' and ground.	11.4 - 14.5 V Go to Step 4	Go to Step 3
3	Replace fuse		Fault is no longer present (fuse not faulty). → End	Fault still present (fuse faulty again). Go to Step 4
4	Inspect the wiring harness from 'F13 fuse output' to compressor relay 'pin A3B (terminal 30)' for pinches and chafing damage.		No damage visible. Go to Step 5	Repair or replace wiring harness. → End
5	Check wiring between compressor relay and level control module for short circuit to B+	Switch off ignition. Pull plug A off level control module. Remove compressor relay 'relay socket 3 in relay carrier at left of dashboard'. Switch on ignition. Measure voltage between level control module plug A 'pins 31, 36' and ground.	< 0.3 V Go to Step 6	Repair or replace wiring harness. → End
6	Check wiring between compressor relay and level control module for short circuit to ground	Switch off ignition. Measure resistance between level control module plug A 'pins 31, 36' and ground.	∞ Ω Go to Step 7	Repair or replace wiring harness. → End
7	Check wiring between compressor relay and level control module for open circuit	Measure resistance between level control module plug A 'pins 31, 36' and compressor relay plug A 'pin 3F (terminal 85), pin 3D (terminal 86)'.	< 5 Ω Go to Step 8	Repair or replace wiring harness. → End
8	Replace compressor relay		→ End	Go to Step 9
9	Replace level control module		→ End