Checking the Electrical Heating In the Rear Windshield (With RTI)
Checking the electrical heating in the rear windshield (with RTI)
Checking equipment
The following fault-tracing applies ONLY to cars with 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
for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault and a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
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 Relay/fuse box cargo compartment/Rear electronic module (REM), replacing Integrated Relay/Fusebox Cargo Compartment/Rear Electronic Module (REM), Replacing.
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 Relay/fuse box cargo compartment/Rear electronic module (REM), 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 blue radio antenna amplifier in the left D-post. Check for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault. Check for a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Check the copper tongue (cable) between the blue radio antenna amplifier in the left D-post and the heating loops in the rear windshield. Check for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault. Check for a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Check the grounding of the heating loops via the white antenna amplifier in the right D-post against the ground terminal for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Check the heating loops for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault. 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 blue antenna amplifier (radio and TV antenna amplifier), See the relevant procedure.
- To access the white antenna amplifier (TV antenna amplifier), See the relevant procedure.
- To replace the rear windshield, see Removing the rear windshield Removing the Rear Windshield.
- Fully functioning heating loops have a resistance of 0.41 ohms at 20°C. If the resistance is higher, one or more of the heating loops are defective.
Was a fault detected?
Yes - Fault Found
No - No Fault Found
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