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Old 05-05-2008, 10:09 AM   #1
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Alternator Trouble

Just double checking,

Got an 88 YJ with I6, starts fine, runs good, turn lights on, and they dim out when idling, shine a little brighter when revved up. Radio also goes out when idling down. Battery is new, just rechecking. Gonna pull alternator and have it tested tonight. Just like checking with the experts on here.

Let me have it.

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Old 05-05-2008, 12:19 PM   #2
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sounds like the alt to me.

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Old 05-05-2008, 01:12 PM   #3
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sounds like alternator.
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Old 05-05-2008, 01:19 PM   #4
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I figured as well, just wanted to make sure. Friday night, I took it to the local poker game at a friend's house and it limped home with it looking like the headlights were actually lit up by flickering candles. Just wanted to make sure...


Thanks for the input...
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Old 05-05-2008, 05:48 PM   #5
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Well, I need more opinions now. I pulled the alternator, took it to OReilly's and had it tested on their machine before purchasing it. The kid at the counter said it had passed the machine test. I told him that I did not believe it, so I asked him to do it again with me standing there watching the test. Came back that it passed the test.

I still did not believe my eyes, so went to Auto Zone right up the road, same thing, passed on their machine.

SOOOOOOOOOOOOOOOOOOOOOOOO, what do yall think I need to check next. Kinda at a crossroads.
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Old 05-05-2008, 06:00 PM   #6
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check if your voltage regulator is seperate on yours. i have a 90 yj here, it wasn't charging, so in a hurry i just threw an alternator at it. didn't bother testing output. i should've brought this up sooner. you can test that alternators function on the jeep easily, just put a volt meter on the big wire at the alternator, if its in the 12's its not charging, if its 13-14.5 or so, its working.

moral of the story is, the jeep here has an alternator thats charging, but its not getting to battery, and voltage regulator is seperate. i haven't had time to look, and computer was vague about the volage regulator, so i haven't found it yet. but i suspect voltage regulator on this one.

check voltage at alternator, and at battery. also, amps are important, but i doubt you have amp meter handy. also, alternators sometimes take longer to show problems than quick bench test. good luck, let us know how its goin. sorry i didn't think of that before you took it off.
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Old 05-05-2008, 06:47 PM   #7
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try to tighten your belt first.
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Old 05-06-2008, 05:20 AM   #8
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Please don't forget one thing.Those high dollar hunks of crap at those stores have are uh well...crap.Those machines do not load test an alternator.They just spin it and get a voltage reading.It's easy to achieve a decent voltage reading when you don't have a load on it.I have a tester at home and i use it all the time for cases lke this.I had a friend with an accord.I bought a new Autozone Alt.Within 2 weeks it started taking a dump.When i tested it,it was putting out 12 amps.I took it back and they put it on thier machine and it passed.Go figure.Damn near had to beat 'em to give me another.I'm not saying this is your case but i don't trust them machines at all and i'm not the only person who has had this same problem.
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Old 05-06-2008, 09:43 AM   #9
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Put old alternator back in tightened everything back down and made sure all connections were tight and cleaned off. Then I went riding around last night with the lights on to test this out under loads. Here is the dilemma. Leaving a store last night, lights kinda flickered for about 15-20 seconds, then got bright as they normally do. This happened two times and I drove around town to get the stop and go driving thing going. After flickering twice in the early part of the drive, the lights did not flicker one bit.

Any takers on this?
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Old 05-06-2008, 01:22 PM   #10
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Ok let's start here.At any point did you take a voltage reading from your battery.Everything points to the alternator/charging system but you said you limped home and the radio cut out.It sounds to me like it was pretty bad.But being that bad did you have to jump start it once you shut it off??New battery or not if the alt. is not working it's gonna kill it.
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Old 05-06-2008, 02:19 PM   #11
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Quote:
Originally Posted by jpdocdave View Post
check if your voltage regulator is seperate on yours. i have a 90 yj here, it wasn't charging, so in a hurry i just threw an alternator at it. didn't bother testing output. i should've brought this up sooner. you can test that alternators function on the jeep easily, just put a volt meter on the big wire at the alternator, if its in the 12's its not charging, if its 13-14.5 or so, its working.

moral of the story is, the jeep here has an alternator thats charging, but its not getting to battery, and voltage regulator is seperate. i haven't had time to look, and computer was vague about the volage regulator, so i haven't found it yet. but i suspect voltage regulator on this one.

check voltage at alternator, and at battery. also, amps are important, but i doubt you have amp meter handy. also, alternators sometimes take longer to show problems than quick bench test. good luck, let us know how its goin. sorry i didn't think of that before you took it off.

in case you didn't read it. test it on the jeep.

are you allowed to quote your own quote????

check battery connections if you haven't already, clean and tighten.
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Old 05-07-2008, 09:35 PM   #12
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Alright guys, took your advice.

89 Strangler, you first, I took your advice and that did not work. I did not have to jump it either, starts like a champ every time.

Dave, tried your stuff too, battery is running 14.3 volts and the alternator reads the same. I don't have an alt meter, not that advanced yet, I guess.

I can check the voltage regulator if I knew what I was looking for. Can you help me out? I am trouble shooting anything at this point. I am just at a loss. I happen to love mysteries and this is an electrical mystery.

BTW, thanks to both of you for your advice.

Guys, keep in mind this is a 20 year old Jeep that I bought from an old boy who did not fire it up since July 06. I am gonna have some headaches, but I like to figure some stuff out and sometimes I need some help.
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Old 05-08-2008, 04:17 AM   #13
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when you hold the rpm's up does it always make your headlights brighter like they are supposed to be?If not ,when does it seem to correct itself?
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Old 05-08-2008, 07:20 AM   #14
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14.3 volts at the battery means alternator is working. can you check it when lights are dim. would be nice to see amps when lights flicker to.
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Old 05-08-2008, 08:38 AM   #15
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I'll give it a shot and keep yall posted...

Thanks for the advice
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Old 05-08-2008, 01:21 PM   #16
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We want amps,We want amps,We want amps.Oh sorry,i was getting carried away.
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Old 05-08-2008, 05:49 PM   #17
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yes, we want amps.
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Old 05-19-2008, 05:47 PM   #18
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How about a disconnected ground wire. I reconnected it and it appears to be idling fine in the yard. Did not run it much, but we'll see
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Old 05-19-2008, 05:52 PM   #19
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ya, grounds work better when they're attached.
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Old 05-19-2008, 08:36 PM   #20
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I love the mysteries of jeeps. Keep turning wrenches until you find the problem...
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Old 05-20-2008, 05:12 AM   #21
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