The battery on my convertiable 5.3 xjs goes flat while parked. Constant current draw of 0.038 amps. Is this significant.Ive pulled all fuses in LH and rh internal fuse boxes. Pulled engine fuses on LH bonnet. Pulled roof motor fuses, as well as all relays I could lay my hand on. Could not get it to disappear. Any ideas.

 

Usual sources of XJS battery drain are:

- boot light (switch on lock not quite engaging). But it is fused
- aerial. An internal fault materialises. Try disconnecting
- Security system. Unlpug ecu

.038 doesn't sound awful. How much does the voltage drop by and over what period? How old is the battery?

Good luck

Paul

 

Battery is only 12 month old. I have only owned car 6 months. Have disconnected batter to let it sit for a few weeks and then try a start. Car does not have a security system. Boot light switch does not get rid of current draw

 

Adding to Pauls suggestions.

The electrical section of the Ignition switches are now becoming very common with other issues, and a simple clean and relube of the internals restores the contact integrity. If those same internals are not actually switching OFF when it should be, then a "leak" will be there and drain the battery.

Battery itself is still on my list, especially up there.

Put a meter on it when its parked and disconnected, should be 12.6 for fully charged. After a week or 2 in that state, it should be the same, or very close.

As Paul has said, 0.038 is fairly close to "normal".

 

Battery is only 12 month old. I have only owned car 6 months. Have disconnected batter to let it sit for a few weeks and then try a start. Car does not have a security system. No boot light either

 

Understand that.

What is the volts of the standing battery?, and then you can gauge the status in 2 weeks. If the volts are the same, then the battery is probably OK, but a load test will determine that, and the V12 is one hell of a load test.

Batteries can die, not common today, but we still get the odd one every now and then fresh off the shelf at work.

 

What size battery did you put in? CCA's or A/h


A 38mA (0.038Amps) current draw is about normal and if the battery was 50amp/hours then the battery should last 14 days (down to 70% charge) before it needed charging, it would go a lot longer than this but discharging LA batteries below 70% will significantly reduce their life.

 

Hi bendougy and greetings from down south. Perhaps you have some reliable documentation for how you know the battery was a brand new replacement 6 months before you even acquired the car. Exactly how? A receipt? Is it documented on your battery? How, exactly? If reliable, and it fails the load testing (especially full load CCA test) being recommended here, it should be covered by a guarantee.

OTOH, one nasty lesson I learned years ago, is that sellers and even (heaven forbid) some car sales staff can have a somewhat amnesic grasp of the truth . . . and even fully detailed sales receipts are no guarantee that the part installed on the car is that which is specified on a purchase receipt. Call me cynical, but car batteries and (when they first appeared years ago) electrodeless iridium spark plugs were easily and readily swapped out . . . latter happened to me on a quad valve Mitsubishi and I was totally unaware until car was next serviced by a different dealer's service shop!

I venture this not to denigrate the overwhelming majority of ethical and helpful people who are the backbone of our industry, but by way of urging you to really examine your battery. Something smells fishier here than the stack of $90 notes I have stockpiled ready for my next Jaguar purchase! As Grant and Warren have said, your QCD is within cooee of normal . . . a tad high but not sufficient to cause such symptoms . . . and your beastie is not even a later gen S-Type whose PCMs really hate anything less than full battery charge and a permanently connected smart charger to keep it that way!

+1 also to Grant's comment that, while modern batteries are generally reliable, occasional failures are known straight off the shelf.

Best wishes,

Ken