Checking Rear Windshield Heating

Checking the rear windshield heating

Fault-tracing information
Rear windshield heating is supplied with power via a relay positioned in the integrated relay/fusebox in the engine compartment.
Reasons for the rear windshield heating not working can include:
- Burnt out fuse
- Damaged relay
- Defective switch
- Open-circuit in the signal cable
- Open-circuit in the heating loop.
For information about fuse numbers and the number on the terminal pins, see the Wiring diagram.

Continue - Checking components

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Checking components
Check that the following components are intact:
- Rear windshield heating fuse
- Rear windshield heating switch.
For information about fuse numbers and the number on the terminal pins, see the Wiring diagram.

Checking the relay
Check that the rear windshield heating relay is correctly installed.
Also check the relay terminal, in particular terminal #5. Check for a short-circuit to ground.
Check the function of the rear windshield heating relay. Activate and deactivate the relay a number of times. The relay is functioning if there is a clicking sound when the relay is activated and deactivated.
Click the VCT2000 symbol to activate and deactivate the relay.
Remedy as necessary.

Other information
- Checking wiring and terminals Checking Wiring And Terminals





Was a fault detected?

Yes - Verification

No - Checking the components and wiring

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Checking the components and wiring
Check the signal cable between the central electronic module (CEM) and the rear windshield heating. Check for an open-circuit. Check for a short-circuit to ground.
Take readings between:
- Central electronic module (CEM) terminal #C28 (#28) and rear windshield heating connector.

Checking the rear windshield
Measure the resistance in the heating loop.
Normal resistance at +20°C for:
- 4-doors, approximately 0.63 ohms.
- 5-doors, approximately 0.76 ohms.
Remedy as necessary.

Other information
- Connecting the breakout box Connecting The Breakout Box, Central Electronic Module (CEM)
- Checking wiring and terminals Checking Wiring And Terminals

Continue - Replacing the component

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Replacing the component
The fault was probably caused by an open-circuit in the heating loop.
Replace the rear windshield.

Other information

Continue - Verification

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Verification




Verification

Hint: After carrying out the repair, check that the fault has been remedied.








- Ignition off
- Reinstall the connectors, components etc.
- Ignition on.
Click the VCT2000 symbol to activate and deactivate the relay.
A click should be heard from the relay.
Check that the function is OK.





Is the function OK?

Yes - VERIFIED

No - VERIFICATION FAILED

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VERIFIED - FAULT FOUND

VERIFICATION FAILED - Fault-tracing information

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Fault-tracing information

FAULT-TRACING FAILED - FAULT-TRACING FAILED

Attempt New Test - Fault-tracing information

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