Rear Window Defogger (Z1), Checking

Rear Window Defogger (Z1), Checking

• If there is a condition that the heating for the rear window cannot be switched on (short circuit in the connection to the Rear Window Defogger Relay (J9) , interruption in the current 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 system to the Climatronic Control Unit (J255) ; this must be read in the DTC memory of the Comfort System Central Control Module using the Vehicle diagnostic tester in "Guided Fault Finding". The rear window defogger (Z1) control is displayed in the comfort system central control module measured value block. Check using the Vehicle diagnostic tester in "Guided Fault Finding".

• If the stored value in the vehicle electrical system control module (J519) or the measured voltage on terminal "30" falls below a value stored in the vehicle electrical system control module or in the Climatronic control module, the rear window heating will be switched off completely (or the power reduced) and by doing so, the load on the generator (C) is reduced. Refer to the Vehicle diagnostic tester in "Guided Fault Finding".

• If the heated rear window must be switched off due to low voltage, the window heater lamp button in the Climatronic control module stays on. If the switch-off lasts longer than 150 seconds, then the Climatronic control module will switch off the indicator lamp.

• The Climatronic control module measured values block indicates that the rear window heating is switched on or why no activation is occurring despite a request. Refer to the Vehicle diagnostic tester in "Guided Fault Finding".

• The function test for the heated rear window control is described in the Guided Fault Finding for the comfort system central control module (J393). Refer to the Vehicle diagnostic tester in "Guided Fault Finding".

• The heated rear window stays switched on at outside temperatures up to 0 °C (32 °F) until ignition is switched off (heated rear window can be switched manually at anytime). If temperature becomes greater than 0 °C (32 °F) during a driving period, switch-off of rear window defogger occurs after the operating time stored in the Climatronic control module has elapsed (approximately 10 minutes). Refer to the Owner's manual.

• The heated rear window is switched off at an outside temperature higher than 0 °C (32 °F) by the Climatronic control module after approximately 10 minutes (activation time depends on the coding and the version of the Climatronic control module). Check using the Vehicle diagnostic tester in "Guided Fault Finding".

• From MY 2010, some vehicles have a Start/Stop System for specific engines as optional equipment. On vehicles with Start/Stop, the rear window defogging can be switched off whenever the Stop function is active (to protect the battery (A) ). The setting for the rear window defogger remains stored in the Climatronic control module. After the engine is started again by the Start function, rear window defogging is switched on again. Check using the Vehicle diagnostic tester in "Guided Fault Finding".