1990 xjs v12 convertible rear quarter windows sometimes fail either up or down , had the mechanism out , and they are jammed at either end of the travel , on powering up on a battery they work fine and refit to car and they work ok for 6 months. anyone got any ideas ?
stripped motors all appears sweet as with no sign of over heating or the 2 grand smell.

I've Read the Kirby book and not much is mentioned about the quarter windows

a suggestion has been to fit a poly switch [ current limiter] in series with one motor wire to prevent them jamming up so tight ?

 

They are both powered and grounded through relays, I bet the relays are failing. Replace with heavy duty 40 Amp relays, not the standard auto 30 amp relays and that should fix it.

 

Welcome the rear window problem world........ Mine has done that since New and l believe that Jaguar tried to fix that with a new part after '93-4 as it has a different part number.
A sharp tap on the motor with a shall hammer will get it working again for a while.

If you use the search feature above you will find a few threads about it.

 

Thanks gentlemen

Relays

I've removed one relay at a time and manually connected battery to the motor at the other to by pass each relay in turn to check at the relay terminals as the relay at rest joins earth to the motor, and the motor just draws current, I also measured the voltage at the motor terminals while activating the relays and it was ok, so I assumed the relays are sweet as.

I'm a little concerned about the tap with a hammer system as the permanent magnets may be damaged and i am guessing the motor regulators are jamming at the end of the travel rather than a dodgy brush or connection within the motor. I pulled one of the motor housings off and was able to turn the motor armature with difficulty then it cam free as it wound away from the jam at the end of it's travel.

I am wondering either using a poly switch as current limit or mechanical limit switches in series with the relay winding. Either so the motors don't jam.

Anyone tried anything that worked long term ?

Kind regards Donald

 

I was in a similar situation, the relays appeared good, but the contacts were burnt and wouldn't pass full current. Interesting how it jams at the end of travel, I've not experienced that.

 

I wonder if the nylon bush that the arm stops against is worn with a taper so it winds itself up rather than a square edge to stop against.
I'm pondering if I use limit switches it will allow the dynamic braking that's been designed to 'lock' the motor and make it stop faster work as designed with the dual changeover relay setup.

 

I have fitted a limit switch to the left hand window down and in 30 operations it has not jammed down [yet].

a simple test is to wiggle the window when down , are yours solid or a little movement up and down ? On this car left is ok after limit switch modification, right is bound

I feel it could do with some current limiting in the up also as by design it is being driven up for about 2-3 seconds when stalled, fortunately it is easily set up due to the wring design.

With both of these modifications I believe the quarter windows mechanism will be unloaded and might last the life of the car.



Kind regards Donald

 

My first post is incorrect, the window only jams down