Possible causes, elimination, notes

Diagnosis conditions 

No control module fault stored.

Voltage too high 

1. Unplug connector C from the heating/air-conditioning control.
2. Connect voltmeter to C 8 and ground. Switch on ignition.

   Display: 0 volts

   If the battery voltage is displayed, check the wiring harness for pinching and chafing damage.

3. Push on connector C.
4. Connect voltmeter to C 8 and ground. Switch on ignition.

   Display: 5 +/- 0.5 volts

   If more than 5.5 volts are displayed, replace the heating/air-conditioning control.

Voltage too low 

1. Unplug connector C from the heating/air-conditioning control.
2. Unplug all connectors from the valve drive motors.
3. Connect ohmmeter to connector C 8 and ground.

   Display: "INFINITY" ohm

   If 0 - 5 ohm is displayed, check wiring harness for pinching and chafing damage.

4. Check potentiometer in the drive motors.

   Temperature mixing valve: Connect ohmmeter to pins 1 and 3.

   Display: 4 - 5 kohm at 23 °C

   Footwell / defrost valve: Connect ohmmeter to pins 1 and 3.

   Display: 4 - 5 kohm at 23 °C

   Central valve: Connect ohmmeter to pins 1 and 3.

   Display: 4 - 5 kohm at 23 °C

   Outside air / recirculation valve:Connect ohmmeter to pins 4 and 5.

   Display: 4 - 5 kohm at 23 °C