Heated Rear Window, Checking

Heated Rear Window, Checking

• 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) front A/C control head, this will be stored as a fault in the control head vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.

• If the voltage measured at the Energy Management Control Module (J644) at terminal "30" falls below a value stored in the control module, the rear window heater is either switched off completely or its output is reduced to relieve the load on the alternator. The Climatronic Control Module (J255) front A/C control head reduces the duty cycle activation from 100% to between 0 and 90% vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.

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

• Measuring value block of A/C control head Climatronic Control Module (J255) indicates that heater of Heated Rear Window is switched on or why no activation is occurring despite a request Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.

• Checking actuation of heated rear window operation is described in guided fault-finding for air conditioner. Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function

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

• When the outside temperature is greater than 0 °C, the heated rear window will switch off automatically once the operating time stored in the Climatronic Control Module (J255) front A/C control head has elapsed approximately 10 minutes. On vehicles with standard glass, the activation time depends on the code in the control head Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function