So I've had my 01 XJ Sport for a couple years. Chased gremlins from the instrument panel, to the catalytic converter. Old Shelly has 233K+ and still runs like a beast. My latest issue is that every 2 or 3 days the battery guage will drop to 9V and she won't charge. The alternator tested good at the parts store. But I'm getting anywhere between 11.3 to 13.9 and its wild. I do have a couple of aftermarket led and halogen fog lights as well as my traffic control beacon. But the draw from those shouldn't have any effect on the output voltage. When it happens I pull the positive battery cable and clean all the connections as well as the terminals at the alternator and power dist box. When I put it all together again is when 13.9V is the output. Can anyone please help? This is driving me crazy.

 

Have you load tested the battery to verify it is good? I have seen dying batteries cause some strange electronic behavior.

 

Thank you, Steve.
In my frustration I'm embarrassed to admit that I hadn't thought about that. But on one occasion I had the battery from my son's import SUV and the same thing happened when I switched them out. I will give your idea a shot, though.

 

I had a similar problem on a Cordoba with a slant six back in the 1980s. The problem was a wire to the alternator grounding out to the case. Tech spotted it arch, he was the umpteenth tech to look at it and everybody else had a weird solution. He ended up polishing up the lug and reattaching, problem solved. I don't think it is the big black cable that goes to the PDC either, however, make sure all of the connections to the alternator are good, clean, and insulated from contact with anything around them.

 

my battery was froze and it acted like that.
I'd make sure the belt aint slipping or the alt isn't starting to lock up...(any belt squealing)...could be the alt going bad as well, neighbor had the parts store test the alt for his daughters car, all tested good. made it 10 miles and the alternator died and left her stranded on her way to a job interview.

 

Well, that was your problem right there!

 

My cordoba had the 360...loved it

 

Actually, those were both bulletproof engines. Not so much on power, but they lasted.

Just funnin' ya!

 

Well it turned out that the alternator was bad. She stranded me on a nasty rural road and after I was towed home the decision was made,(by the big boss) a new alternator was installed, (by the cheap mechanic), and we get a steady 14.3V. Lol

 

I really don't trust the parts store tests as the post I made earlier shows there not always accurate. I do my best to test things before throwing parts at a vehicle, but some times ya have to just go with your gut on things. glad it's fixed thow.

 

Seriously, man. They did. They ran it 3 times, checked out and I fell for it. But, honestly if I hadn't I wouldn't have thought to join. So it all pans out, and I now have a place to look for ideas and help to keep Old Shelly roaring down the road. I might mention that I'm heavy on the right and aggressive in maneuver no matter where I am. So sometimes I need to fix a little booboo on the Gray Girl. Thanks guys