Thread: Rear Power Windows - NOT fixed

I posted on Iain b's thread in which he told of a fix for the problem I have. That problem being that my rear windows don't work.

I got the glove box out only to find that the D2a is quite different from the Disco in Iain's thread ie, there doesn't appear to be a separate ecu as there is in his.

Looking at RAVE, it seems that they are controlled by the BCU, I had a mate check the BCU with his Nanocom and there were no faults. Any ideas where else I should be looking? (yes, the fuses are fine). If Nanocom shows no faults, is it reasonable to assume that there is no problem in the BCU? I also read somewhere that you can't just change BCU's as they are preset to the VIN, is this correct?

Doesn't really bother me that much, but my big black dog would love to be able to stick her nose out from time to time.

Originally Posted by biggin

If the switches are like others in the D2, you will find that they are not powered as such, but provide a path from a BCU input to earth. When the BCU then detects the earth path, it will activate the window motor from a BCU output terminal on a separate circuit.
The first thing I would check, is to ensure the switch makes a path to earth when operated. Obviously a bad earth connection will prevent it from working.
Once happy that this circuit is okay, you need to ensure that the BCU is switching the corresponding output to power the motor.
This can be tested by measuring voltage across the output to earth.
If the output is switching, check for voltage at the window motor. If present, window regulator is probably u/s and needs to be replaced, if no then a cable or connector fault is likely.
I can't give you any specifics as I have no access to RAVE at the moment, but will try to help later if you wish.
Good luck.

Okay, you can ignore what I wrote above.

I went off half-cocked without checking the schematics.

Anyway, the rear windows are not controlled by the BCU, but are hardwired via a number of fuses, the ignition switch, and a relay.
With fuses all okay (fuse links 1,6 and 8 in engine bay fuse box, and fuses 13 and 29 in cabin fusebox), the ignition in position II, and the relay (R3 in cabin fusebox) working, there should be 12v to all rear window switches (ie switches on the console AND on the doors) via the white/pink wires.

Activating any of the switches puts power onto the window motor. The current will travel through the motor in either direction, dependant on whether up or down is selected.

If the rear window isolation switch is off, it prevents a return path to earth when using the rear door switches only, therefore preventing the motor from running. In other words there will be 12v on the motor when the door switches are operated, but lack of a path to earth will prevent current from flowing. The earth path is not interrupted using the console switches.

Hope this makes sense Wardy.