battery drain

[pmurf]

hello all. i posted in the new arrivals section but maybe get more luck here. i have a 1998 4.0L that reads completely normal on a discharge diagnostic test. however, if left for more than three days the battery drains enough to stop the car from starting. on boost it fires with no problem and the car runs perfectly well so long as its started every couple of days.

has anyone come across this sort of situation before? all help gratefully received.
Paul

[mike020150]

Hi, XK8 electrics are complicated so issues like this one may take a while to solve. Patience is a necessity when the diagnostics kit can't give an immediate answer. 3 days to empty a battery of juice is unusually quick and indicates a significant current flow. I assume that you've had a battery drop test carried out to ensure it's in good health; that you're using a battery of at least the Jaguar recommended capacity and you do not leave the keys in the ignition switch. Owners, (particularly just prior to a sale!) can be tempted to fit smaller, cheaper batteries but the hassle isn't worthwhile. The most obvious culprit is the boot light switch and/or its timer device. Failing that there are several circuits which remain live if the key is left in the ignition in the off position and for a period of time after it is removed. If you work through the fuse boxes methodically, removing fuses either one at a time or initially several together to identify the circuit or group of components responsible, you should be able to find the guilty circuit. Good luck. Mike.

[dredr62]

Might also want to check the mirror lights in the sun visors. Sometimes the mirror cover fails to turn the light off and the visors get nice and warm and the battery nice and flat.

[painter]

pmurf,
had the same problem recently, over 10 days whilst on hols. the (new) battery had drained sufficently to throw warning codes and too flat to start.
Left with Jag. dealership for a couple of days and traced to the wiring loom in door, small discharge but enough over 10 days to run down. Cured now, but could be rain water passing window seals = condensation/damp in door.