Rear Window Defogger

NOTE:

Various vehicle electrical components (for example, Rear Window Defogger -Z1- and heated seats) that do not belong to the heater are activated by the Climatronic Control Module -J255- A/C display and control head. On the Rear Window Defogger -Z1-, for example, the turn on request is sent via the Data Bus to the Comfort System Central Control Module -J393-, the Comfort System Central Control Module -J393- then controls the Rear Window Defogger -Z1- via the Rear Window Defogger Relay -J9-. Refer to the appropriate SYSTEM WIRING DIAGRAM. Electrical testing of these components must be performed as described in Guided Fault Finding for the A/C system and the Comfort System Central Control Module -J393- using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.

If there is a condition that the rear window defogger may not be switched on (short circuit in the connection to the Rear Window Defogger Relay -J9-, interruption in the power supply to the Comfort System Central Control Module -J393- etc.), this will be stored as a malfunction in the Comfort System Central Control Module -J393- and the information will be sent via the Data Bus to the Climatronic Control Module -J255- A/C display and control head; this must be read in the DTC memory in the Comfort System Central Control Module -J393-, using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. The Rear Window Defogger -Z1- activation is displayed in the Comfort System Central Control Module -J393- measured value block, using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.

If the current at the Vehicle Electrical System Control Module -J519- or the measured current on terminal "30" falls below a value stored in the Vehicle Electrical System Control Module -J519- or in the Climatronic Control Module -J255- A/C control and display head, the rear window heating will be switched off completely (or the output reduced) and by doing so, the load on the Generator -C- is reduced, using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.

If the rear window defogger must be switched off due to low voltage, the rear window defogger button indicator lamp in the Climatronic Control Module -J255- A/C display and control head stays on. If the switch-off lasts longer than 150 seconds, then the Climatronic Control Module -J255- A/C display and control head will switch off the indicator lamp.

The Climatronic Control Module -J255- A/C display and control head measured values block indicates that the rear window defogger is switched on or why there is no activation despite a request, using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.

The function test for the rear window defogger activation is described in the Guided Fault Finding for the Comfort System Central Control Module -J393-, using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function

The rear window defogger stays switched on at outside temperatures up to 0 °C (32 °F) until ignition is switched off (rear window defogger can be switched manually at anytime). If the temperature becomes greater than 0 °C (32 °F) during a driving period, the rear window defogger is switched off after the operating time stored in the Climatronic Control Module -J255- A/C display and control head has elapsed (approximately 10 minutes). Refer to the Owner's Manual.

The rear window defogger is switched off at an outside temperature higher than 0 °C (32 °F) by the Climatronic Control Module -J255- A/C display and control head after approximately 10 minutes (activation time depends on the coding and the version of the Climatronic Control Module -J255- A/C display and control head), using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.

From MY 2010, this vehicle has a Start/Stop System for specific engines as optional equipment. In vehicles with a Start/Stop System, the rear window defogger can be switched off while the stop function is active (to protect the Battery -A-). The setting for the Rear Window Defogger -Z1- activation remains stored in the Climatronic Control Module -J255- display and control head. After the engine is started again via the Start function, the rear window defogger is switched on again, using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.