Heated Glass Element: Testing and Inspection

Heated Rear Window, Testing

• If there is a condition that prevents the rear window heater from switching on, such as a short circuit in the connection to the rear window or an open circuit in the voltage supply to the Climatronic Control Module (J255) A/C control head, this will be stored as a fault in the Climatronic Control Module (J255) A/C control head => Vehicle Diagnosis, Testing and Information System VAS 5051.

• If the voltage measured at Energy Management Control Module (J644) at terminal "30" falls below a value stored in the Energy Management Control Module (J644), the rear window heater is switched off completely e.g. by the Vehicle Electrical System Control Module (J519) (or is regulated to a lower performance level), which relieves the load on the generator. => Vehicle Diagnosis, Testing and Information System VAS 5051.

• The heated rear window is activated by the Vehicle Electrical System Control Module (J519) only when the engine is running. If the engine is at standstill there is no return message from Vehicle Electrical System Control Module (J519) and the LED lamp in the button on the Climatronic Control Module (J255) A/C control head goes out for a short time after pressing again.

• If heated rear window must be switched off due to insufficient voltage, indicator lamp in heated rear window button on A/C control head Climatronic Control Module (J255) remains switched on, however if switch-off is to last longer than approximately 150 seconds, A/C control head Climatronic Control Module (J255) switches off the indicator lamp.

• The measured value block of the Climatronic Control Module (J255) A/C control head displays that the Heated Rear Window (Z1) is switched on, or why no activation is occurring despite a request => Vehicle Diagnosis, Testing and Information System VAS 5051. However, since the Heated Rear Window (Z1) is activated by the Comfort System Central Control Module (J393), errors in function, voltage supply and activation of rear window heating are not detected or displayed by the Climatronic Control Module (J255) A/C control head => Vehicle Diagnosis, Testing and Information System VAS 5051.

• The function test for the heated rear window control is described in the guided fault finding for the central control unit for comfort systems (J393)=> Vehicle Diagnosis, Testing and Information System VAS 5051.

• With outside temperatures greater than 0 °C the heated rear window is switched off automatically by A/C control head Climatronic Control Module (J255) after the programmed operating time (approximately 10 minutes) in A/C control head Climatronic Control Module (J255) has elapsed.

• The heated rear window stays switched on with outside temperatures up to 0 °C until ignition is switched off (heated rear window can be switched off and back on manually at anytime). If the temperature becomes greater than 0 °C during a driving period, switch-off of the Heated Rear Window (Z1) occurs after the operating time stored in the Climatronic Control Module (J255) A/C control head has elapsed (approximately 10 minutes).

• Depending on the version of the Climatronic Control Module (J255) A/C control head, the "rear window on" function is saved when the ignition is switched off, and switched on again when the engine is started.