Planning the next
AO Silver Member
Join Date: May 2007
Location: United Kingdom
The climate control unit doesn't have a lot to do with the Heated Rear Window. All it does is host the switch and LED. The actual control of the HRW is done by the N82 Integrated Services Unit behind the glove box.
In practice what happens is that when the HRW switch is pressed it signals N82 to energise the HRW relay and N82 then initiates a timer ( to automatically switch off the HRW ) and switches on the LED on the climate control unit. In addition, when the direction control is turned to 'MAX', the climate control system again signals N82 to switch on the HRW.
Therefore, unless there is a physical fault with the HRW switch on the climate unit, the fault will be elsewhere -
a. the wiring between the climate control unit and N82
b. in the N82 unit itself.