Just read this in Rave:
"Automatic operation
The HRW also operates in an optional automatic mode. When the engine is started and the BCU receives an engine running message on the 'K' bus from the instrument pack, the BCU monitors the ambient temperature and the engine coolant temperature. If the ambient temperature is below 10°C (50°F) and the engine coolant temperature is below 40°C (104°F) the BCU will automatically energise the HRW relay and illuminate the HRW switch LED and operate the HRW timer for the appropriate time (dependent on external ambient temperature) or until a HRW OFF condition is encountered.
If the BCU senses a default engine coolant temperature of 50°C (122°F) and/or a default ambient temperature sensor value of 11°C (52°F), the BCU will continue to operate the HRW on these values although automatic operation will be suspended.
On high line vehicles with ATC, automatic operation will also occur if any of four fresh air or recirculation fault codes are active. The BCU uses the information received from the ambient temperature sensor, via the instrument pack, to determine the period for which the HRW is to operate. The engine coolant temperature is ignored in this instance.
This automatic operation will occur to prevent the windows misting if the ATC ECU cannot correctly control or establish the status of the recirculation flap."
Notice it says
optional, so how does one turn it off?
