Disco 2 Passenger window will only go up

Hi everyone thanks for taking the time to reading about my problem.
I have a 2002 Discovery 2 and I thought my passenger window was totally dead as nothing would move. I bought a new regulator mechanism as the plastic wheel had broken with age.
After taking it all apart and having the motor free of the mechanism, I tried operating it with the switch. This was when I discovered that the motor would only run in one direction.
My first thought was that the switch might have failed so swapped the drivers side and passengers side and it made no difference and the drivers one worked fine.
I saw that motors were quite cheap and bought a new one but it still does the same. I have assumed it its not a fuse but as its still moving.
I was just wondering if anyone could shed some light on this. After a bit of a search I am getting concerned by the possibility of the BCM and wouldnt know where to start if it was that!
Any feedback would be most appreciated.

It sounds like you are on the right track, it is the BCU that switches polarity and nothing else.
soz. mate!

If you have confirmed motor and switch are ok it could well be a BCU issue, but I would check door loom for any damage first, particularly at the umbilical.

Hi, seems very like BCU issue as if it works one way means that the wiring to the motor is OK as there are only two wires and the BCU switches the polarity to revert the motion.... unfortunately the only way to rule it out is to replace the BCU and for that you need a nanocom or similar to program it, there is a slight chance to be a wiring issue between the switch down position and BCU input to C0662 -1(black/red wire) so you have to identify that pin, insert a needle into it in situ and connect to body with a wire, if no reaction then the BCU is at fault... you'll have to remove the glovebox to get there... though if you hear a faint click from the BCU when you switch the window down dont even bother with this test

Thank you all for your replies, looking at the wiring diagram kindly posted it cant really be much else. I have checked for dodgy wires etc but it all looks OK. I have found a few companies offering replacements that are cloned from the original and just plug and play. I shall send it off and see what happens.

miniac said:

I have found a few companies offering replacements that are cloned from the original and just plug and play.

Click to expand...

Be very cautious with this to not end up scammed, plug and play BCU? that is quite unbelievable to me... i'm wondering how can a BCU be cloned from the original which is faulty and on the vehicle while each vehicle has it's own characteristics which are subject of BCU settings?... eventually go for a repair service with your's if you can't find somebody with nanocom or similar to program a good used one, seems more realistic

I do wish I had read that last post before taking the unit to the post office and waving it bye.
I sent it off on Thursday and they examined it today (Wednesday) and sent me an invoice for the exchanged unit that is now in the post back to me. I shall let you all know if it really is plug and play and hopefully my window will now go down too!

OK, i misundertood first time that they send you a BCU without getting your's first... as long as they can access your BCU then it's possible to "clone" it if it's not completely fubar, even better is to be repaired

I thought I would just give a quick update for anyone who might read this with a similar issue in the future.
I have a BCU back which is fully functional and I am back on the road.
I sent it to a company called Turners Mechatronic. I would advise finding a different company to do this for you!
To be polite I would say that the chap is not a people person. The three day turn around was two weeks and the price was far greater than on their website with no reasoning behind it. The google reviews make an interesting read too.

Thanks for update. It hurts that service was not as hoped, but at least problem solved.