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Jaguar Repair/1981 XJS Jaguar


Hi Howard,

I have not succeeded in getting the windows to go in my 1981 XJS coupe.
However after reading an article in the "online  Experience in a book", a guide for the XJS owner, I found that if I remove the window relay and connect the power to the windows directly, Both windows work perfectly.
This is of course with the ignition off. Is this safe or should I add a fuse as the circuit is constantly live. If so what size fuse should I add. I do prefer do be able to open the windows when the keys are not in the car.

Thanks and regards


Hi Paul.

The windows are not powered all the time. The power comes from the right hand power terminal in the firewall to a thermal breaker then to the window relay mounted on the back of the relay panel next to the passenger's side fuse panel. This relay is not activated until the ignition switch is in position # 1 or # 2. Even though there is power at the relay all the time, the relay only allows power to the windows when the ignition switch is ON.

By jumping the terminals #30/51 (power) to #87 (output to load) you bypassed the relay and proved that part of the system if ok. (this is a test that most mechanics would have done to diagnose the problem. If you used an external power source, check #30/51 (brown w/blue tracer wire for power as that is the thermal breaker power supply. The thermal breaker is mounted on the lower right of the relay panel and may have a amps rating written on it.

Now you have isolated the problem down to either the relay itself or the #85 and #86 circuits have a failure.

Your next test should have been to test the black wire in #85 socket position to see that it is a good ground. Then test #86 to confirm that it is powered with the key in position 1 & 2. If this is all true, then you need to test the relay as this indicates a failed relay.

I would not recommend powering the windows with the key in the OFF position, but that is not my car.

Let me know,


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Howard M. Fitzcharles III


Jaguar from the XK 120 to XJ-6 ser. 3 1987


Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Associate member SAE EAA member

Import Car magazine

ASE Master Auto with L-1 certification up to 2000

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