David
I replaced a power window motor this year, here's some things I found doing the job:
Firstly - I will say, having had a few fail over the years, and bought a few 2nd-hand ones which were fairly knackered as well, that even if the motor is kaput, it's probably less hassle to refurbish it than get another: it's usually simply about opening the motor up, cleaning the gunk out, cleaning the contacts, and lubricating the bearings. There's not a lot to go wrong, apart from the electrical contacts and the bearings. These motors seem to fail not because of overuse - they hardly run for hours like a washing machine motor - what gets them is moisture, corrosion, dirt. This job is very easy and straight forward, even if you know nothing about electric motors.
But you'll have it get it out of the door to do this, or replace it, so...
I suggest during the initial disassembly to leave the motor itself on the diecast piece it attaches to. There's three bolts (10mm I think) which attach that diecast piece to the pressed steel of the window scissor frame - those three bolts are on the door-skin side, rather than the inside, feel for them if you can't see them. Remember, once those are out, the window glass may want to fall down, so use something to stop that.
Before getting to repairing the motor, I will say that I found it really difficult to replace the motor with the scissor frame still in the door - access was poor, couldn't see anything and couldn't get the three bolts to thread in, so I think it's probably less frustrating to take the scissor frame out, get the motor assembly onto it, then get it all back in and re-assemble.
To get the scissor frame out: let the window glass down manually (now freely movable because the motor is gone) to the point that you get access to the three connection points between glass and scissor frame - they are sprung loaded clips. Obviously once those are free, use something to hold the glass up and out of the way, then fold the scissor frame flat so it can come out of the hole in the inside door frame.
Once this frame is out, it's a good chance to lubricate and free-up all the pivot points in it.
With the motor and its diecast attachment which houses the gearing: it's probably more common to keep those together, and replace them as a unit. But - it's easy to separate motor and cast and definitely worth attempting to refurbish the motor. One thing from memory is that one of the bearings for the motor is in the cast, so it doesn't just all fall apart as soon as the bolts are out, but work it out and it'll come. Plus while it's all open, you can get some grease onto the gearing inside the diecast case.
As I said, the motor will probably just need cleaning up inside, carbon brushes cleaned non-abrasively, the commutator polished with very fine (def 400+) sandpaper, and bearings greased. This would probably fix most: as I said, it'll be corrosion and gunk not over-use which will get these motors. Of course, all the pivot points in the scissor frame and all other moving parts in the assembly will also need lubricating, to make the job easier for the motor.
Hopefully that's useful for you.
John
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