I've had it on the charger all day, and will re test tomorrow. As soon as I've got actual numbers I will put them up. Thanks again.

 

OK I have the same kind of problem with my XK8 2000 jag. The battery will not start the car I had a trickle charger on it and it was not working as in starting the car. I just checked the voltage with the car off the battery reads 13.84 volts and when I jump start the car with it running the meter reads 21.5 volts so I would assume my alternator is working? I have no warning lights that are telling me that the alternator or charging system is no functioning. I did get abs warning no trac asc warning that went away after I restarted the car. What to do?

 

21.5Volts?! I was under the impression that a healthy alternator puts out around 14 ½ V, and would guess a 13.85V battery would start the car. For laughs, check your meter on another car. While waiting for others to chime in about those readings, perhaps look at the state of your battery and starter connections – loose or corroded?

When you say "won’t start the car", what do you mean exactly? When you turn the key: is there no sound? just a clicking sound? the starter turns over sluggishly? the starter spins at a normal cadence but the engine doesn’t light?

 

If you accidentally hook the battery up backwards like I did you will fry the regulator and may not see the charge light as that is where the light comes from , different then the dash voltage value meter .

 

Not sure where you're reading 21.5 volts, but if it's directly on the battery terminals, then you likely have a dud cell or more - which would explain the no-start - althoug I'd expect all manner of spurious lights and messages with that voltage.

Would also do no harm to clean the battery terminals, together with a check of the connections around the high power protection module in the boot/trunk, as they're known to come loose.

There's a picture of its location in this post by GGG:

https://www.jaguarforums.com/forum/x...7/#post1832034

Lady P - I'd be surprised if you could see anything for at least 10 minutes if you tried to hook up the battery reverse polarity LOL

HTH

 

Yes I was getting 21.5 at the battery terminals and they look clean no corrosion. I just checked the voltage again and now without the car running it reads 12.58 so I have something draining the battery. When I go to start the car and turn the key there is nothing even the windows when you open the door do not move. When I jump start it I have to wait a minute or so to turn the key or I just get a click I wait a minute or so with the jump cables on it and it starts right up...The battery is little over 1 year old from AAA. We do not drive the car enough it can go days without being driven. I just had the gas pump replaced a few weeks ago and I also had the bumper and hood painted the guy had to remove the bumper so maybe the issues are from these repairs???I also have purchased the parts to replace the gas purge valve as the car will smell of gas after 20 mins of running...This car is never ending excitement LOL..Thanks for all the input I love this forum. I do not have enough experience with the car to give advice but I am getting there...

 

Just over a year isn't old, but it sounds like an internal issue with the battery. You could measure the voltage across the terminals while the motor is cranking, but it would be easier just to get the battery load-tested.

ABS/TRAC errors after start that go away of their own accord are another symptom of a failing battery.

I take it you're a fan of the genius that was Hendrix?

 

Yes love Hendrix! BTW my wife car only has 46k on it...I am going to take it to get the battery tested. The 21.5 volts is really weird not sure why that is happening. I will post when I get an answer . Thanks again for the response!

 

There is no way 21.5 volts is correct. I would expect something around 14 - 15volts max. If your alternator is putting out 21.5 volts something is broken and your battery will be fried in short order.

 

I replaced the battery tonight. The guy I purchased the car from last year lied to me and told me he just replaced the battery and even gave me a receipt for a battery just not the one that was in the car. The battery was 5 years old AAA battery. So I called AAA to see if they would honor the warranty and was turned down so I had to shell out $200 for a battery...nice. Karma will get that guy!

 

Thanks again for everyone that chimed in and gave me help!