I bought my 1998 xj8 2 weeks ago! It came with a brand new installed alt, and battery, however battery light remains on, and battery not charging is constantly shown in the system msg! But it is clearly holding charge and no issues! Could this just need to be shut off with scanner or can it be reset another way? Any help is greatly appreciated!

 

Probably an aftermarket alternator. I ran two different autoZone ones on a 3.0L S-type for a couple of years. (Lifetime warranty, and I convinced them the pulley was off-center before finally figuring out the harmonic balancer was delaminating) but anyway, both exhibited that behavior - Batt light always on, but voltage output was good, always kept the battery charged. But it was my daughter's car and when she went to college about 6 hrs away, I bought a used one from a wrecking yard and put the AutoZone one in a box on the shelf. Everything works normal since.

 

I had same problem after alternator went

Tested alternator, ground, battery not charging light stayed on

Car drove fine

It turned out the dash unit shorted out

There is a business on eBay - if you ship them the dash unit ( removes easily)
They will rebuild the circuits and replace the bulbs. Price is reasonable

Check voltage from alternator to dash - if a charge and light is on - then most likely the dash unit. If no charge from alternator - maybe a bad diode in alternator

Also,check battery ground


Good luck

 

Awesome! Thanks for the replies! I've heard similar about aftermarket alt, I have checked ground on battery, and it' appears to be okay! I will check my connections on the alt tomoro! I'm hoping for an easy fix! Car charges and runs fine! Cranks awesome! Just that damn light is annoying! And if it is something, I'd rather fix it then drive and pretend/assume it's okay because no obv symptoms lol! I will post tomoro what ever I conclude, if anything! Thank u

 

This problem has shown up on the forums previously. There are two slightly different charge light indicators, I think you have the wrong one for your car.
A forum search should give more information.

 

Attached is a picture or the indicator!

 

Maybe diagnostic scanner can get rid of the warning on the dash or maybe you could disconnect the battery for a few hours to see if it resets.

 

So what is this about alternators from autozone causing false alternator failure warnings? I am about to get an alternator from there so that kind of throws some warning bells off !!!! I am in an X350, but my warning light came on too. Codes blew up all over the place, luckily I made it home. I checked the battery voltage and sure enough, it was dead. I trickle charged the battery and car started up fine, no codes. Then battery light came on again after a few days and fault codes began popping up. Worst thing is I just had the car in for service and alternator checked out fine. Two weeks later, not so fine.

 

I think the problem is that they're not actually compatible but are "close". Close isn't good enough.

 

Hrrrmmmm...I think then a rebuild would be better. And less expensive.

 

Yeah, I don't know! When I bought it the guy had kept all the service and repair reciepts, and the alternator installed was 468$ labour and parts! And I've recently installed hids, which on start up if one ballast doesn't go on, it throughs abs and traction failure, then I shut off and restart and both ballast go on and codes go out lol! I love the jag! But they r deff finikey

 

OK...here is the fix !

I installed a direct replacement alternator in my 1998 XJ-8 . The Battery Not Charging message immediately came up on the display. I checked voltage at the battery ..... 14 volts. I have been using a cigarette lighter plug with digital voltmeter to monitor all this time.

Here is the problem: there are two wires going into the plug on the back of the alternator. The white wire is supplying voltage to the field and the gray wire should be sending voltage to the instrument panel. With the car running, only 3 volts was present on the gray wire. I cut the gray wire at the plug and connected it to the white wire...light on the dash is out and confirmed that there is still 14 volts going to the battery. Seems to me that someone changed the design of the voltage regulator at some point.

Be sure to check the voltage on the gray wire with the engine running before you cut it...if you see 12 to 14 volts present, you have other problems most likely.