Symptom Related Diagnostic Procedures
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.
Continue - Checking components
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Checking components
Check that the following components are intact:
- Rear windshield heating fuse
- Rear windshield heating switch.
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)
- Signal specification Signal Description, Central Electronic Module (CEM)
- Control module relay box passenger compartment Service and Repair
- 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
- Rear windscreen Service and Repair
Continue - Verification
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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 - Troubleshooting procedure complete
No - Fault-tracing information
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Fault-tracing information
Information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.
Do you want to exit fault-tracing?
Yes - Exit Fault-tracing
No - Attempt New Test
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