There are several threads on this one in the forum and I too have suffered from the seized rear window problem on both my Carltons.. I intend to edit this post to add more information as I get to understand more about the window lift control system, and probably add some pictures.
I have been determined to find the root cause of the problem with the back window lifts breaking, because sooner or later there will be fewer and fewer Carltons in the breakers and we won't have a ready supply of replacements at a fiver each (that's what my local scrappy charges for ten minutes of my work to take one out, I've had plenty of practice!).
So this description is intended to be as full and complete as I can make it so that we can keep our cars in good nick with everything working.
Description of problem -
One or both rear windows refuse to work, even with the override button pressed down.
If there are other issues such as none of the windows working and the fuse is OK, then the problem may lie in the switchgear in the centre console as described in
http://totalcarlton.com/forums/index.php?topic=982.0 Diagnosis - Choose somewhere reasonably quiet to do this check. Press the button on the door or in the centre console and listen, you should hear a click from the door as soon as you press the button and another click after about two seconds. The first click is the control system pulling in one of the two relays in the black control box which is attached to the window lift. The second click is the overcurrent limiter dropping the same relay out. There is one relay in the control box for 'UP' and the other is for 'DOWN'.
So in summary, pressing the window button results in two clicks a couple of seconds apart and no movement of the window.
Repair - Remove door card and window lift mechanism from the door by drilling out the rivets (BTW a pop riveter is all you need to put the mechanism in properly, see
http://www.machinemart.co.uk/product.asp?p=040213150&r=2084&g=111, 3/16 rivets are the size needed)
You'll also need a Torx bit (30 I think) to take apart the motor / gearbox assembly.
It is a good idea to try the window lift buttons again before disconnecting the lift from the harness in the door, if it works when disconnected from the glass then there's a good chance that it will seize up again when reassembled, unless you follow the rest of this post, (that has happened to me, take it off - works, reassemble, either doesn't work or works for only a few days)
Feel the motor housing to make sure it is warm, warm is OK, if it is cold, try the switch a few times, if the motor never gets warm, you need a new motor, easy enough to change but you'll need to follow a lot of what is in this post anyway.
Reassembly of the gearbox is a little fiddly as the lift cable will certainly unwrap itself from the drum, but in doing this repair it also proves that if the cable breaks (and it does happen), then the cable is replaceable independently of everything else.
With the lift mechanism out of the door, take off the gearbox cover plate by removing the torx screws, one screw doesn't go through the cover, leave that in for the time being.
Take the screws out that hold the motor to the gearbox, and gently remove the motor by pulling in a straight line, at the end of the motor shaft is a very small diameter extension (about 1mm) which goes into the unit mounted on the gearbox opposite the motor, I think this unit is the current limiter sensor.
What I found on the ones I have taken apart is that the gearbox is full of what look like wood fibres and the worm on the motor shaft is clogged up and the nylon worm wheel cannot rotate in the gearbox owing to a lack of lubrication and all the fibres in the gearbox.
The drum with the cable attached will probably come off at this point and the cable will unravel, beware there are three small U shaped rubber parts in the drum which will drop out. These are vibration isolators and cushion the drum mechanism from the worm wheel. All these bits need looking after.
Remove the final torx screw from the gearbox housing and lever off the top half of the case.
Clean all the nylon fibre out of the gearbox housing and brush the nylon wormwheel to remove all the junk off that. Check the wormwheel to make sure that it still has teeth!.
Clean the steel worm on the motor shaft making sure you don't bend the thin extension shaft.
Put the wormwheel back in the housing with the drive components (not the drum)
Lubricate (I used a PTFE spray a bit like WD40) the gearbox
Put the gearbox plastic top half back on and put the single screw in
Gently push the motor back into the housing and fasten onto the gearbox housing.
I used a white grease spray to hold the U shaped isolators into the bottom of the drum, wind the cable back onto the drum (you really need three hands at this point :-( ) As the cable is the right length you cannot make it too short or too long it just goes back in the right place.
Put the gearbox lid back on and replace all the screws.
Reconnect to the harness and test.
Lubricate the window slides from inside the door, just to be on the safe side.
Refit the lift mechanism into the door (easier said than done!).
Test again, with the glass attached.
Note how the motor pulls the glass down without 'labouring', but going up the motor sounds like its working hard.
Hopefully you now have a working window (or two)
Root Cause - I suspect (having listened to the front windows which never stop working in this way, at least not in my experience) that there is an engineering geometry problem with the rear windows which loads up the lift mechanism, when new its not a problem, but after ten years or so when the window has gone up and down a few thousand times and the lubricant has dried out then the accumulation of nylon fibres basically clogs up the gearbox and the window stops working.
Keeping our cars on the Road - I haven't checked yet, but I would expect to find the same gearbox on many European GM cars, as the only bit that actually wears is the wormwheel then we should be able to strip down other window lift mechanisms to get at the wormwheel.
I hope this helps everybody out there with stuck windoze ;-)
Cheers
