Howdo, my 98 xkr is intermittently showing this message so I assume its the alternator, possibly battery . Any other ideas please? the gauge shows 13volts whether the light is on or off .

*battery

 

Forget the gauge to start with. Use a volt meter, car at rest 12.6v, engine running should be 14.1v.

Check the connector at the alternator is clean, dry and properly seated and make sure the battery terminals are clean and tight.

 

The gage is not very accurate, but when I got the "battery is not charging" light on my '97 XK8, I was able to drive it about 17 miles before systems started shutting down one by one.


Mine was definitely the alternator. Swapped the alternator with a $35 one from a junkyard XJ8.


A couple days after the alt swap I again got the "battery is not charging" message, but it was because I also swapped a coolant hose, and spilled coolant on the serpentine belt and it slipped off the pulley when the car started. Put the belt back on and no problems since.

 

Ungn did well, he was fortunate. I strongly advise you to but a Denso (OEM) alternator if replacing. I went through 2 AutoZone alternators before I found a Denso for $225.

John

 

If you were local Dallas, TX, I'd pick you up a $35 Alternator at the junkyard this weekend. There is currently a '00 and '01 XJ8 in my local yard. For $10 more they offer a "2 year warranty".


My current one is from a '02 XJ. It maybe used, but it's 5 years newer than my original.

 

Thanks all, I can't find my voltmeter but have had it charging all evening. I'll book it in .

 

I originally thought it was my battery going out, but tested it under load after charging it and it was fine. The alternator appeared to have been undercharging it for a while (without more than just a flash "battery not charging" warning) making the battery seem flaky for weeks before the "battery not charging" came on and stayed on.


9 months after swapping alternators, using the same old battery, the battery now seems excellent.

 

Ive got the message up again today but I'm reading 13.8 v with everything on , 11.8 with engine off.

 

Not much help here but normal charging voltage is 13.8 -14.2v
Regards,

 

11.8 with the engine off is too low, especially if the battery is charged overnight on a 2 amps.

The alternator could be intermittently bad, but the battery should be 12.5V or higher if its in good shape. Below 12.5v, a lead acid battery's power goes down quickly and accessory load can drag the voltage down low enough to throw a light.

A proper AGM battery showing 12.0 volts at rest only has 45% of the charge of a new, fully charged battery and is low as you'd ever want to repeatedly take down an AGM battery. (11.80 is 30% and is in the Battery damage range)

 

Thanks a lot! very interesting. The car had been sat for 9 months when I bought it .

 

I had the exact same trouble the other day. It was about four month after I bought the car that had been sitting almost a year at the shop. It was charging, the voltage was normal even with the message "not charging" appeared intermittently.
Some days later, suddenly I got all warning lights turned on while driving (engine was running) and the voltage went as high as 18V and I shut the car off immediately.
The issue caused by the regulator failure in the alternator.

 

Thanks, a battery is arriving tomorrow- but regliator looks possible too. I just did 10 miles, with the message on for 8 of them. Got home, checked and its still showing 13.8.