Fault code 31: Diagnosis/troubleshooting

FAULT CODE 31 DIAGNOSIS PROCEDURE

Work instruction			Display OK	If not OK
1	Check fuse D6		Step 2	Replace fuse
2	Check relay for fresh-air blower	Switch off ignition Remove relay for fresh-air blower Switch on ignition Measure voltage at relay socket between pin 3 (terminal 30) and ground Measure voltage at relay socket between pin 3 and pin 2 Measure voltage at relay socket between pin 2 and pin 7	Battery voltage Step 3	Check line between fuse D 6 and relay socket for open circuit/ short circuit to ground.
3	Check relay for fresh-air blower	Switch off ignition Remove plug B from the air-conditioning system regulator Reconnect heating activation once more Switch on ignition Measure voltage between plug B 11 and ground	Battery voltage Step 4	Relay for heating activation faulty or short circuit to ground or open circuit in the line between heating activation relay and the air-conditioning system regulator
4	Check blower regulator (end setting)	Switch off ignition Reconnect plug B to the air-conditioning system regulator Switch on ignition Bridge terminals K2 and K3 on blower regulator Switch on blower	Fault has been remedied Step 5	Step 6
5	Check blower regulator (end setting) and line for air-conditioning system regulator	Switch off ignition Remove plug B from the air-conditioning system regulator Remove plug from blower regulator Measure resistance between plug B on the air-conditioning system regulator pin 12 and plug on blower regulator pin K 1	< 5 Step 9	Repair wiring harness -> End
6	Check line to blower motor for short to B+	Switch off ignition Remove plug from blower motor Switch on ignition Measure voltage between plug on the blower motor pin L2 and ground Measure voltage between plug on the blower motor pin L1 and ground	0 V Step 5	Repair wiring harness -> End
7	Check line to blower motor for short to ground	Measure resistance between plug on the blower motor pin L2 and ground	Step 6	Repair wiring harness -> End
8	Check line to blower motor for open circuit	Switch off ignition Measure resistance between plug on blower motor pin L2 and plug B on air-conditioning system regulator pin 10 Measure resistance between plug on blower motor pin L1 and plug B on air-conditioning system regulator pin 11	< 5 Step 10	Repair wiring harness -> End
9	Replace blower regulator		-> End
10	Replace air-conditioning system regulator		-> End