Signal Too Low
Signal too low
Checking the function of the rear defroster
- Ignition on
- Read off the status of the defroster relay
- Activate the rear defroster switch on the climate control module panel.
Check that the status changes when the switch is activated.
The fault is intermittent if the status changes when the switch is activated.
Has the status changed?
Yes - Intermittent fault
No - Checking connectors
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Checking connectors
- Ignition off
- Check the defroster relay base for position 1 and climate control module connector A (30-pin). Check for contact resistance and oxidation. Remedy if necessary.
Check for damage carefully
- Reinstall the components, reconnect the connectors etc.
- Ignition on
- Read off the status of the defroster relay.
Activate the rear defroster switch on the climate control module panel. Check that the status changes when the switch is activated.
The fault was caused by loose connections in the connectors if the status changes.
Other information
- To remove the control module, see Comfort module Removal and Replacement
- To access and replace the defroster relay, see Replacing relay in central electrical unit in passenger compartment Replacing Relay In Central Electrical Unit In Passenger Compartment
- Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault
Has the status changed?
Yes - FAULT FOUND
No - Checking the cable and component
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Checking the cable and component
Check the cable between climate control module terminal #A25 and defroster relay position 1 terminal #2. Check for an open-circuit and a short-circuit to ground.
Check fuse number 12 (15A) in the integrated relay/fusebox in the passenger compartment.
Check that there is power to and from each fuse when the ignition is on.
Try a new defroster relay if the wiring is OK.
Remedy as necessary.
Other information:
- To access and replace the defroster relay, see Replacing relay in central electrical unit in passenger compartment Replacing Relay In Central Electrical Unit In Passenger Compartment
- To connect the breakout box, see Connecting the breakout box, climate control module Connecting The Breakout Box
- For the voltage of the signal cable, see Climate control signal specifications Signal Specification
- For the resistance values, see Electrical / electronic system specifications [1][2]Specifications
- Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault
Continue - Verification
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Intermittent fault
Check the climate control module connector A (30-pin) and the defroster relay base for position 1. Check for contact resistance and oxidation.
Check the cable between climate control module terminal #A25 and defroster relay position 1 terminal #2. Check for an intermittent open-circuit and an intermittent short-circuit to ground.
Other information:
- To access and replace the defroster relay, see Replacing relay in central electrical unit in passenger compartment Replacing Relay In Central Electrical Unit In Passenger Compartment
- To connect the breakout box, see Connecting the breakout box, climate control module Connecting The Breakout Box
- For the voltage of the cable, see Climate control signal specifications Signal Specification
- For the resistance values, see Electrical / electronic system specifications [1][2]Specifications
- Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults
Continue - Fault-tracing information
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Fault-tracing information
Information
Fault-tracing information
If the fault is intermittent, do not verify fault-tracing if the fault does not recur.
It is possible to view the information again, or leave fault-tracing for this diagnostic trouble code (DTC).
Do you want to view the information again?
Yes - Attempt New Test
No - FAULT FOUND
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Attempt New Test - Checking the function of the rear defroster
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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
- Read off the status of the defroster relay
- Activate the rear defroster switch on the climate control module panel
- Check that the status changes when the switch is activated.
The fault has been remedied if the status changes.
Has the status changed?
Yes - FAULT FOUND
No - VERIFICATION FAILED
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VERIFICATION FAILED - Fault-tracing information
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Fault-tracing information
Information
Fault-tracing 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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Attempt New Test - Checking the function of the rear defroster
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