Checking the Electrical Heating In the Rear Windshield (Without RTI)
Checking the electrical heating in the rear windshield (without RTI)
Checking equipment
The following fault-tracing applies ONLY to cars without Road Traffic Information (RTI) systems.
Is the test applicable?
Yes - Checking the main fuse and wiring
No - No Fault Found
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Checking the main fuse and wiring
Check that rear main fuse 11E/5 is intact.
Check the wiring between:
rear main fuse 11E/5 terminal #2 and relay 2/82 terminal #5
relay 2/82 terminals #5 and #1
and for an open-circuit or short-circuit to ground.
Remedy as necessary.
Other information:
- For further information about signals and other values, see Signal specification Pinout Values and Diagnostic Parameters
- To access the integrated relay / fusebox in the cargo compartment, see Integrated relay/fuse box cargo compartment/rear electronic module, replacing Integrated Relay/Fusebox Cargo Compartment/Rear Electronic Module (REM), Replacing
- Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Was a fault detected?
Yes - Fault Found
No - Checking the relay
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Checking the relay
Check the function of relay 2/82: 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.
Replace with a new relay if the relay does not function.
Other information:
- To access the integrated relay / fusebox in the cargo compartment, see Integrated relay/fuse box cargo compartment/rear electronic module, replacing Integrated Relay/Fusebox Cargo Compartment/Rear Electronic Module (REM), Replacing.
Was a fault detected?
Yes - Fault Found
No - Checking components and wiring
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Checking components and wiring
Check the cable between relay 2/82 terminal #3 and the broad flat terminal pin on the red radio antenna amplifier in the left D-post. Check for an open-circuit. Check for a short-circuit to ground.
Check the copper tongue (cable) between the red radio antenna amplifier in the left D-post and the heating loops in the rear windshield. Check for an open-circuit. Check for a short-circuit to ground.
Check the grounding of the heating loops in the right D-post against the ground terminal. Check for an open-circuit.
Check the heating loops. Check for an open-circuit. Take readings between the copper tongues (cables) in the left and right D-posts.
Hint: An open-circuit can only be detected if none of the heating loops are functioning.
If only some of the heating loops are defective, these can be identified by activating the heating for the rear windshield, then breathing on the rear windshield at each heating loop. The condensation will disappear more quickly at the heating loops that are functioning.
Remedy as necessary.
Other information:
- For further information about signals and other values, see Signal specification Pinout Values and Diagnostic Parameters
- To access the radio antenna amplifier, see the relevant procedure.
- To replace the rear windshield, see Rear window removal Rear Window Removal
- Fully functioning heating loops have a resistance of 0.41 ohms at 20 degrees C. If the resistance is higher, one or more of the heating loops is defective
- Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Was a fault detected?
Yes - Fault Found
No - No Fault Found
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