XJS Draining battery

[KeithViolet]

I have an 89 xjs that the battery will drain in about 5 days if I don`t run it. Any ideas ?? or common problems with this car problem.

 

[Bugeye58]

This may sound silly, but make sure the light under the hood, as well as the one in the trunk, and the glovebox lamp all go off when the things are closed. I know of several people who have had this problem, and many times it turns out to be something as simple as the glovebox lamp staying on! Or a visor vanity lamp.
You know the battery is in good shape, I assume? You have a parasitic draw somewhere, and the obvious things are the best place to start.
Jeff

 

[Steve]

A common problem with the XJS of that vintage is that the seat belt motor would keep kicking in when sitting with the ignition off. It would not operate as normal, but keep clicking the belt holder against the stop at the end of its travel, and drain the battery. I think it was the relay, rather than the motor. I think there may have been a service bulletin about this.

 

[John S Farrington]

Regarding the electric drain on an XJS; the normal drain for this car is about .03 amps with all accesories off. Common causes of drains over this amount are alternator defects, seat belt passive restraint motor continuing to run, and simple things like lights with stuck activating switches. To isolate the drain, set up the battery cables with a 10 amp meter in line with the battery. Begin to pull fuses or disconnect items until you find the culprit that is causing over over a .03 amp current from the battery. When this happens you have isolated the problem and you can focus on trouble shooting/ fixing it. The XJS is a simple car to conduct this procedure. The largest problem is undocumented fuses. Get a good wiring diagram of the car and the in line and undocumented fuses will be identified. Good luck in finding them. Best regards, Jack Farrington