I have been trying to salvage my window regulators and motors. One works, the other does not. I've swapped parts between the two motors and have isolated the problem to the 'base' of one of the motors. There is a small component on there that one end ties directly to 12v and is labeled 'MICROTHERM'.
Can I bypass this? After cleaning all the little components, making sure no wires or coils are broken, I think this is the culprit. The one motor that works has this same little MICROTHERM component and the little plastic housing was filled with water (I was assuming it was water) but it was not corroded at all. The other one was dry and corroded.
Not sure if any of this makes sense but here are some images. I think this could also save folks some £££ (or $$$). Sorry Photobucket won't rotate the images.