I've been having some issues with an uncooperative driver's window. It runs strong with no struggle, but twice this summer it's refused to go back down after startup. Fearing the motor had bitten it after troubleshooting the switch, I did some research and found a veritable Rube Goldberg circuit full of thermal breakers, a 'master switch', and other components where maybe a fuse would have done just fine.

Since both times the window has gone unresponsive it started working just fine once things had cooled off, I'm starting to suspect the thermal breaker and it looks like I could just get a 20A automotive circuit breaker in there. Is that at all a feasible fix, or should I be looking elsewhere?

 

A generic 20amp automotive circuit breaker should be fine.

Dirty/weak connections anywhere in the circuit are always a possibility.....and especially likely when the failure is so sporadic.

Poor contacts inside the window switch are common.

Physical/mechanical binding of the window itself is not unheard of, especially if the felt channel is breaking up.

Cheers
DD

 

Thanks for the input, Doug. I'm all but convinced the deficiency is heat-related, and the only things I'm sure of is the switch and the integrity of the felt channel. If we get a reprieve from the rain I'll dig behind the door card and report my findings.

 

we are working on the same problem. what a nightmare of wires and relays i have narrowed mine down to weak motor on an 88 that sat for 8 years and a possible ground issue. When you get panel off the wires for the motor is right there very easy to put one to ground to see if motor will work or if it is binding in channel. to get it to go back up just reverse order of ground it it will go other way also you can check the whole system at that plug switch operation and power .

 

Well, I spent a couple hours playing with the circuit, and it looks like it is the motor. From the switch all the way through the motor, everything is fine. The motor is getting ample power, it just isn't doing anything with it.

So much for my "it works just fine when cool so it must be the thermal breakers" theory.

 

All of the XJS window motors suffer from the same problem....after 20+ years the carbon builds up on the armature and the brushes begin to loose connection. They then become intermittent or inoperable.

Take the motor apart and clean the brushes and armature. Make sure you mark the magnet can and put it back on in the same position. If you reverse the can the motor will run in the wrong direction.

Once you clean the armature and brushes it will work like new.

Mark

 

ok thanks that is todays project

 

well I cleaned the motor contacts and all the problem is now the same thing good thing ac works

 

I had similar window problems when I first got my 89 xjs. I took the motors and their mounts out, cleaned all the channels, bench tested the motors with a 12v charger and everything worked fine.... But I also had a problem with the window switches. cleaned those and bench tested. All work fine now. BTW, you might also be getting some engine heat into the channel housing the gear selector and window switches, etc, but I don't see how that would cause any motor problems.... Yes, the fuse could be "week" if really thin, but they normally blow..... I have a couple of extra motors I took off of a parts car I had for a while... If I can dig them out, I will bench test the driver's side and let you have it at a discount from whatever the going rate is, plus give you "return if it does not work" and $$ back...

Ken in Wild and Wonderful West Virginia..
Putting my "Candance" in the Pittsburgh car show in a few weeks...

 

I might just have to take you up on that... I'll know by the weekend for sure.