Heated Rear Window

WARNING: This page is about a different car, the 2020 Jaguar XE and 2019 Jaguar XE. However, it is still accessible from the selected car via links, so may be relevant.

The BCM /GWM controls the operation of the heated rear window using a relay in the Rear Junction Box (RJB). When a request is made for heated rear window operation, the ICP broadcasts a message to the BCM /GWM . The message is transmitted on the HS CAN comfort systems bus. On receipt of this message, the BCM /GWM energizes the relay by providing a ground path for the relay coil. This allows a power supply to flow across the relay to power the heater element.

There are 2 modes of heated rear window operation. The manual and the automatic modes.

Manual operation is activated by operating the heated rear window switch on the ICP . When the switch is operated, the status Light Emitting Diode (LED) in the switch illuminates and the rear window heater element is energized.

Manual operation is discontinued when:

The heated rear window switch is operated a second time.
Between 5 and 21 minutes have elapsed (dependent on ambient air temperature).
The engine stops.

If manual operation is discontinued by the engine stopping, the previous heating phase is resumed if the engine is started within 30 seconds.

There are 2 modes of the automatic operation. The automatic operation at the start of a trip and the automatic operation during a trip.

Automatic operation at the start of a trip is initiated for between 5 and 21 minutes (dependent on ambient air temperature). When the ambient air temperature is higher, the operation time of the heater will be shorter.

In addition to shorter operating times there are condition qualifiers to prevent subsequent operations:

The passenger compartment or engine is warm.
There is a significant heat from the sunbeam.

Automatic operation is discontinued if the heated rear window switch is pressed or the system stops. Note: Automatic operation of the heated rear window can be selected ON and OFF on the Settings page of the Climate menu in the Interactive Display Module 'A' (IDMA). Automatic operation during a trip is initiated when low ambient air temperatures are experienced and the vehicle has been traveling for a set period of time above a threshold speed. In this instance, no feedback is given to inform the driver that the heated rear window is operational (the status LED in the switch is not illuminated). The duration of operation is variable depending upon the ambient air temperature, vehicle speed and the amount of time the vehicle has been traveling.