Rear Window Defogger -Z1-, Checking: Procedure
WARNING: This page is about a different variant/trim than selected.
The rear window defogger is switched on via the button -2- on the Heater Control Module -J65- /A/C Control Module -J301- -A- or Climatronic Control Module -J255- -B- control head.
- By pressing the button -2- with the ignition switched on, the control head (Heater Control Module -J65-, A/C Control Module -J301- or Climatronic Control Module -J255-) activates the Vehicle Electrical System Control Module -J519- via the Data Bus. As soon as the Vehicle Electrical System Control Module -J519- switches on the rear window defroster (only when the engine is running on vehicles without a high voltage system), the lamp in the button -2- comes on. The Vehicle Electrical System Control Module -J519- sends the request via the Data Bus. The rear window defogger is switched off by pressing the button again or by switching the ignition off. Refer to the Owner's Manual. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function and refer to the appropriate Wiring Diagram(s).
- The Rear Window Defogger -Z1- is activated by the Vehicle Electrical System Control Module -J519- via the Rear Window Defogger Relay -J9- on vehicles without a high voltage system only when the engine is running. On vehicles without a high voltage system if the engine is not running, there is no activation or message from the Vehicle Electrical System Control Module -J519-. The lamp in the button does not illuminate or goes out again shortly after pressing it. Refer to the Owner's Manual. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
- On vehicles with a high voltage system the activation of the rear window defogger when the drive ready mode is active depending on the engine. It is activated in electric driving mode (with the engine off) in the same way as on vehicles without a high voltage system with the engine running.
- The Rear Window Defogger -Z1- switches itself off by the Vehicle Electrical System Control Module -J519-, for example when the outside air temperature is higher than 0 °C (32 °F) and after about a 10 minute operating time that is stored in the Vehicle Electrical System Control Module -J519- using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
- The Rear Window Defogger -Z1- stays switched on with outside temperatures less than 0 °C (32 °F) until ignition is switched off (it can be switched on and off manually at any time). If the temperature becomes greater than 0 °C (32 °F) during a driving period, the Rear Window Defogger -Z1- is switched off after the operating time stored in the Vehicle Electrical System Control Module -J519- has elapsed (about 10 minutes).
- If the rear window defogger button is pressed for a long period of time when turning on the rear window defogger, the rear window defogger remains switched on until the button is pressed again or the ignition is switched off. Refer to the Owner's Manual.
- If, for example, the Vehicle Electrical System Control Module -J519- voltage measured at terminal "30" falls below a value stored in the Vehicle Electrical System Control Module -J519- or in the control head (Heater Control Module -J65-, A/C Control Module -J301- or Climatronic Control Module -J255-), the output is reduced or the rear window defogger switched off completely to reduce the load on the Generator -C- using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
- If the activation of the Rear Window Defogger -Z1- must be switched off due to low voltage from the Vehicle Electrical System Control Module -J519-, the lamp in the rear window defogger button remains switched on in the control head (Heater Control Module -J65-, A/C Control Module -J301- or Climatronic Control Module -J255-). However, if the deactivation lasts longer, the Vehicle Electrical System Control Module -J519- switches off the request to activate the lamp in the control head button and the lamp in the button goes out.
- For vehicles with the Start/Stop System, the rear window defogger can be switched off to protect the Battery -A- when the stop function is active. The setting for the Rear Window Defogger -Z1- actuation remains stored. The rear window defogger is switched on again as soon as the engine is restarted via the start function using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function (for the Vehicle Electrical System Control Module -J519-).
- The Guided Fault Finding "Read measured values" function for the control head (Heater Control Module -J65-, A/C Control Module -J301- or Climatronic Control Module -J255-) shows that the rear window defogger is switched on or why it was not activated even though there was a request using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
- The function test of the rear window defogger activation is described in the"Guided Fault Finding" for the Vehicle Electrical System Control Module -J519- using the Vehicle Diagnostic Tester.