Test Point 12

Test point 12
Motor, fresh-air fan
Voltage too low
Voltage too high

DTC 31

Diagnosis conditions
No control module fault stored.
Supply voltage OK.
Nominal fan voltage > 3 Volt.
Nominal fan voltage stabilised.

Voltage too low

NOTE: Voltage too low means that the measured fan voltage is less than the nominal fan voltage.

1. Check the heating activation relay.
Battery positive voltage must be present at terminal 87 when the ignition is switched on.
2. Pull off connector C on the heating/air conditioning control.
3. Connect voltmeter to C 14 (plus) and ground.
Switch on ignition.
Display: Battery positive voltage

4. Push connector C on the heating/air conditioning control.
5. Connect voltmeter to C 14 (plus) and C 11 (minus).
Maximum fan speed
Display: approx. 12 V

Minimum fan speed
Display: approx. 0 V

6. Connect voltmeter to C 14 (plus) and C 16 (minus).
Maximum fan speed
Display: approx. 5 V

Minimum fan speed
Display: approx. 9 V

7. Check driver.
Connect voltmeter to plus and pin 3 on the driver connector.
Display: Battery positive voltage
Connect voltmeter to plus and pin 1 on the driver connector.
Maximum fan speed
Display: approx. 5 V

Minimum fan speed
Display: approx. 9 V

Connect voltmeter to plus and pin 2 on the driver connector.
Maximum fan speed
Display: approx. 12 V

Minimum fan speed
Display: approx. 0 V

8. Check wiring from the heating/air conditioning control to the driver for continuity.
9. Check fan motor.

Voltage too high

NOTE: A higher fan voltage can be caused only by a short to ground on the wires on pin 1 or pin 2 of the driver.

1. Pull off connector C on the heating/air conditioning control.
2. Pull off connector on the driver.
3. Connect ohmmeter to C 16 and ground.
Display: Infinity Ohms

4. Pull off connector on the fan motor.
5. Connect ohmmeter to driver connector pin 2 and ground.
Display: Infinity Ohms