928 Fan Final Stage Plug Diagram

ohm

3.) Engine-compartment lid switch Pin 6, plug II and pin 7, plug I Engine-compartment lid closed Reading: « ohm Engine-compartment lid open Reading: 0 ohm - 20 ohm

4.) Temperature switch intake/ automatic transmission

Intake temperature > 87.5°C

Reading: 0 ohm

Intake temperature < 82.5°C

Temperature switch, automatic transmission

> 110°C reading: 0 ohm < 105°C reading: ® ohm

If the values stated are not reached, the sender in question is defective.

Function-testing the flap positioning motor

With a length of cable, connect pin

7 (ground) of plug I to pin 5 (0%) of plug I (approx. 2-4 seconds).

The flap positioning motor moves to the 0% position.

Connect pin 7, plug I and pin 2, plug II (approx. 2-4 seconds).

The flap positioning motor moves to the 30% position.

Connect pin 7, plug I and pin 1 (100%) (approx. 2-4 seconds).

The flap positioning motor moves to the 100% position.

If the flap positioning motor fails to assume one of the positions stated, use an ohmmeter to check the conductivity of the control unit -flap positioning motor wire harness.

If the wire harness is OK the flap positioning motor is defective.

19 - 24 Function-testing Flap Positioning Motor

Function-testing the output stage

4.) Function-testing the control signal of the output stage.

1.) Plugs I and II must be connected to the control unit.

Reconnect output-stage plug connector. Remove cover from plug I of control unit.

2.) Checking voltage supply.

Engine temperature< 79°C{ 175°F)

Measure the voltage with an analog voltmeter with an external resistance (Ri) 100 kOhm.

Ignition on

Press AC button

Set the air-distribution slide switch to up/down.

Reading: approx. 7 V

2.) Checking voltage supply.

Connect voltmeter to pin 3 (ground) and pin 4 (plus) of the fan output-stage plug connector.

Reading: battery voltage

3.) Connect voltmeter to pin 3 (ground) and pin 2 (plus).

Ignition on

Reading: battery voltage

Function-testing the 19 - 25

Output Stage

Ignition on

Press AC button

Set the air-distribution slide switch to up/down.

Reading: approx. 7 V

If both fans refuse to operate when the AC button is pressed while the ignition is on, the output stage is defective.

19 - 26 Function-testing the output Stage

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