Windshield Heater (Where Fitted)

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2012 Jaguar XFR, 2012 Jaguar XF, 2011 Jaguar XFR, 2011 Jaguar XF, and 2010 Jaguar XFR. However, it is still accessible from the selected car via links, so may be relevant.

Windshield heater operation is only enabled when the engine is running. The automatic temperature control (ATC) module controls operation of the windshield heater using two relays in the engine junction box (EJB). When windshield heater operation is required, the automatic temperature control (ATC) module broadcasts a message to the central junction box (CJB) on the medium speed controller area network (CAN) bus. On receipt of the message, the central junction box (CJB) energizes the relays by providing a ground path for both relay coils. This allows a battery feed to flow across the relays to power the windshield left and right heater elements.

There are two modes of windshield heater operation; manual and automatic.

Manual operation is activated by pressing the windshield heater switch on the integrated control panel. When the switch is pressed, the status light emitting diode (LED) in the switch illuminates and the windshield heater elements are energized. Manual operation is discontinued when the windshield heater switch is pressed a second time, 5 minutes have elapsed (the heating phase), or the engine stops. If manual operation is discontinued by the engine stopping, the previous heating phase is resumed if the engine is re-started within 30 seconds.

There are two variants of automatic operation; automatic operation at the start of a journey and automatic operation during a journey.

Automatic operation at the start of a journey is initiated if the ambient air temperature is below 5 °C (41 °F). In this instance, the switch light emitting diode (LED) is illuminated and the heater elements are energized for 6.5 minutes. Automatic operation is discontinued if the windshield heater switch is pressed or the engine stops.

Automatic operation during a journey is initiated when low ambient air temperatures are experienced and the vehicle has been travelling for a set period of time above a threshold speed. In this instance, no feedback is given to the driver to inform him the windshield heater is operational (the switch light emitting diode (LED) is not illuminated) and the duration of operation is variable depending upon the ambient air temperature, vehicle speed and the amount of time the vehicle has been travelling.