2005 XJR

It's weird......

The car will start normally for a week or two, then randomly the battery is dead.

I carefully check that there're are no lights on, door ajar, glovebox closed etc.

I put in the new battery - same thing.

It seems the car has a random battery draw that starts on its own.

Any ideas where to start?

Thanks all,

Rob

 

I see from a post below that an open diode in the alternator could cause this. Is there a test for this, or just replace the item and see?

Rob

 

Also check the flap in the ignition switch. Spray a bit of grease in there. A tiny bit and do not stick the tube in the flap.

Hold it open w/ a tiny screwdriver or pic. Then work the grease in and out with the key.

 

Open alternator diode, will not let the battery discharge, with the negative battery cable disconnected.

 

Thank you all,

Rob

 

What about a random intermittent starter motor. I've had one pack up intermittently before it went out completely (not a Jag :-) ) That's why AA Rescue hit them with a long pole, which of course never worked for me. (The Professionals! I Love It)
(the theory being that nudging a brush at the end of it's life just might get it to work)

What about not charging. Car would run for a while. The manual shows a battery symbol for charging indicator, though my X358 only seems to have a red light above the message centre (speedo).

Call me paranoid, but one of these is cheap, easy to understand, and indicates battery charging or state.
https://www.banggood.com/Auto-Car-12...r_warehouse=CN
(Jag) approx 14.5v dropping to 13.5v after 5mins from startup.
at rest, ~12.6v would be a full battery, 12.2v would be 1/2 charged.

If your car is not a daily driver, everyone (I claim to speak for everyone) says you should keep it on a trickle charger.

Please let us know what you find eventually. BTW, if you bought a new battery and accidentally ran it flat, it will now be damaged (less capacity) though not necessarily a write-off depending on how long it was left flat.

 

Starter can draw the battery down, it also has a constant hot, just not quite as likely.