Land Rover Repair: LR D2 window problem, jumper wires, bcu

Question
QUESTION: Hello John.
I own a Disco 2004 SE with 120km.  My driver's window stopped working (stuck up) a few months ago.  The BCU is clicking when I try to operate it in both directions.  I spent the afternoon troubleshooting it.  I benchtested the motor and it's ok.  The switch is also ok, tested on the RH window.  Also, it seems one of the wires from the BCU is grounded, is this normal ?

If I use jumper wires on the motor wires directly from the BCU it make the window run only in one direction.  If I disconnect the LH motor, the RH window stops working.  

Is my BCU toasted ?

Thanks.
Francois

ANSWER: I can't tell if the BCU is bad from your description.  The BCU grounds one wire and powers the other to run the motor up or down; the sequence just reverses to change direction.  You should get a wiring book - either by subscribing to the factory site or by buying a print manual - and test the wiring continuity.  If that is good, and the motor works as you say, you are left with a bad BCU

I think that will be a straightforward series of tests

---------- FOLLOW-UP ----------

QUESTION: Hello again John.  Thanks for the fast reply.

Then, if one of the wires between the BCU and the motor is grounded, that would explain the BCU failure and the fact that even using new wires it's not working ?  

I have the wiring diagram and those 2 wires should not be grounded anywhere.

Francois

Answer
How do you know the wire grounded?  By testing at the window motor with BCU plugged in?  That does not tell you anything abnormal.  The only way to determine that is to disconnect the cables at the window and BCU and measure them (resistance end to end, to each other, and to ground)  in that state.  My guess is, the grounding is taking place in the BCU.  If the wire has indeed shorted to ground that would be unusual and it would likely ruin the BCU