is it my alternator????

I have an 88 Limited with a 4.0 and auto. Up until this afternoon the voltmeter always showed either slightly above or below 14 volts when running. I hopped in it about a half hour ago and it wouldnt go above what looked like 11 volts. I checked the battery and it had 12.06 V and when I started it it dropped to about 10 and went back only to 11.81 V. It seems there is also a slight noise (rub/squeak) coming from the alt. I have to figure this one out soon, but I'm not lookin forward to wrenchin in 9 degree weather.... :wierd: thanks if anyone has any hints or guesses...

bearings. MOST likely in the alt, but could be in any of the pullies. As soon as you get home, remove the belt and try moving all the pulleis by hand. They should all move freely/easily. (I JUST went through the same thing).

the belt was moving freely, but I think the bearings may be shot in the alt. but would this cause the low voltages that I saw? DO you guys know if the Autozones can test the alt on the car or does it have to be removed? thanks

soulslngr said:

the belt was moving freely, but I think the bearings may be shot in the alt. but would this cause the low voltages that I saw? DO you guys know if the Autozones can test the alt on the car or does it have to be removed? thanks

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Just b/c the belt moves, doesn't mean its not having a hard time doing it. AZ can test it, but it has to be removed and tested on their bench. The easiest way to check if its the bearings is to move it by hand, with the belt off. If THAT pully moves fine, check all others.

I put my voltmeter on the battery while it was running and the voltage was only 11.81 I believe. If the alt was working shouldnt this be between 12 and 14 volts? I am pretty sure it has gone to the big alt graveyard in the sky... :bawl:

I had an alt bearing go bad and it made a lot of noise. I think your alt has gone bad, but before replacing it check electrical connections, especially the engine to body ground.

The system should read 12v with the engine off and around 14 while the engine is running. The alternator may spin freely by hand, but that's with the engine off. Put the alternator under load (lights, cpu, etc...) and it gets harder to turn. My point... I don't know. I would say it's your alternator.

Not to belabor the obvious, but before going too much further, make sure the belt is REALLY TIGHT ENOUGH. If you're not used to the XJ serpentine belt, it's hard to believe how tight it really needs to be. Quick test = pinch belt at top, longest unsupported span, between thumb and forefinger, and try to twist it. If it goes past 90 degrees it's too loose.

If you wonder where the squeak is coming from, get some brake fluid and apply it to the belt while it's running ( a pump squirt bottle is nice for this). If squeak goes away, it's a slipping belt. Brake fluid will wear right off and do no harm to belts.

I went out on a limb and went and got an alt last night. braved the 7 degree morning here and got it in (man it's tight gettin it out and in). started everything up and back to just over 14 volts. Yeah I usually put belts at about just turning 90 on longest run but when I first got the truck I was still amazed at how tight the belt had to be. Thanks for all the suggestions and tips. Has anyone upgraded the wiring from alternator to PDC? I was wondering if I should do this too.

http://www.olypen.com/craigh/charge.htm
here ya go!