Rear Heated Window Problem.

[andy vash]

My heated window doesn’t work. I have 12v at the window and there is continuity so l know the tracks in the window are ok. But if l unplug the earth to the window, the brake lights come on, so l assume l have an earth problem.

Can someone offer guidance on where to look, or have any of you had this problem?

[western]

check the earth points for each set of rear lights, behind the cover panels in each rear corner, they should be attached to the wheelarch top face panel & check for broken wire where the rear screen heater & wiper wires pass through the rubber conduit at the door hinge line.

[andy vash]

I’ve check the earths and they look ok, but I’ve sussed out how the brake lights are getting power. The heated window tracks share the same earth as the high level brake light. When l switch on the heated rear window (although power is going to the window) it doesn’t work, but if l unplug the shared earth on the window the brake lights come on, is this normal?

[western]

doesn't sound correct, brake lights should only come on when the pedal is depressed, moving a earth wire shouldn't light them up. 

[DaveSIIA]

If the shared earth is the only path to earth then yes 12V will feed back through the circuit to the next earth. Does the high level brake light operate normally when the shared earth is connected? If not, there will be a poor path to earth somewhere between the door frame and body (needs to be better than just the hinges).

[andy vash]

Yes, when the shared is connected the brake light works as normally. The problem is the heated window doesn’t work.

[western]

Have you extracted the wires from the rubber boot that goes between the door hinge line & rest if the vehicle, still think you have a broken earth wire, try a new earth wire from the screen earth terminal to a known good earth point, if the heater then works, you know what the fault is.