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Unread 10-30-2012, 09:03 AM   #1
semipro06
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alternator wont keep charge

ok for some reason and i ahve switched two alternators in the last month. as im driving down the road. when im stopped at a red light or a drive thru my jeep all of a suddden it stutters hard and trys to die and the charge guage inside moves up and down. what could cause this i have disconnected all my extra wiring and custom work. and still does it. this is all started after one of my coworkers and i had noticed i had an oil leak and we couldnt find it so he had me power wash it and i thought he what he was talking bout but fail to tell me to covor my alternator when i did it. but now there is a new one in it and its still doing it. what could be the cause?

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Unread 10-30-2012, 09:11 AM   #2
Donnyd21
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Ecu
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Unread 10-30-2012, 09:50 AM   #3
ratmonkey
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I've washed many alternators.

Have the battery and alternator checked at your local parts stores. I'd they're good then it's the engine computer.
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Unread 10-30-2012, 09:51 AM   #4
ratmonkey
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Check all battery wiring too... But it's usually the computer with voltege going crazy
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Unread 10-30-2012, 09:56 AM   #5
semipro06
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Quote:
Originally Posted by ratmonkey
Check all battery wiring too... But it's usually the computer with voltege going crazy
So would check it its 93 AutoZone said it doesn't have a plug to where they can check it on the computer
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Unread 10-30-2012, 12:23 PM   #6
Oldfrog
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Dont let an autozone employee TOUCH the PCM.
No way to check it, anyway. It's either good or it's not.
I have gotten two bad alternators in a row before. Check the alternator and battery, then the connections. If it still isnt charging, it's the PCM.
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Unread 10-30-2012, 01:40 PM   #7
ratmonkey
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Quote:
Originally Posted by semipro06 View Post
So would check it its 93 AutoZone said it doesn't have a plug to where they can check it on the computer
not the ecu, the alternator...
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Unread 10-30-2012, 04:50 PM   #8
ozzy_2_me
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Unread 10-30-2012, 05:26 PM   #9
Foundrydude
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If idle drops like the vehicle is about to die, the volt gauge should move a volt or two. That's normal when the engine is stumbling because the alternator won't charge much at 250 engine RPM.
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Unread 11-12-2013, 04:15 PM   #10
blackjack12982
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OK, bringing this back to the top...

94 ZJ w/ a 5.2L. Rebuilt alternator will not charge on the vehicle, but bench tested at O'Reilly's and it tests good. Two different working PCM's don't change anything. Battery is fully charged, but will discharge slowly while engine is idling. Anyone have any new ideas?
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Unread 11-12-2013, 06:12 PM   #11
rlcii77
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Quote:
Originally Posted by blackjack12982 View Post
OK, bringing this back to the top...

94 ZJ w/ a 5.2L. Rebuilt alternator will not charge on the vehicle, but bench tested at O'Reilly's and it tests good. Two different working PCM's don't change anything. Battery is fully charged, but will discharge slowly while engine is idling. Anyone have any new ideas?
Be sure the belt is not slipping on the alt. pulley... Is it the correct pulley on the alt.? I ask because I thought I read or heard something about different sized pulleys causing an issue with either an alt. or power steering pump, can't quite remember for certain... Double check all the wiring and maybe the fuses... Good luck...
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Unread 11-12-2013, 06:30 PM   #12
Gearhead31
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were the cables checked? heavy corrosion would slap down the voltage traveling through. Lower voltages(low rpm idle) wouldn't wanna pass through but higher voltages(fast driving/highway driving rpms) would pump enough power to overcome the corrosion. Ya never know, sometimes the simple questions are the best ones
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Unread 11-12-2013, 07:03 PM   #13
Scopez
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Ever since I did bigger grounds, my ZJ runs so much better at idle. I use to not be able to run my air at idle, it'd kill my battery gauge. Now I have no issue.
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Unread 11-13-2013, 12:38 AM   #14
Oldfrog
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Check the alternator grounding point on the bracket. Then plan on replacing the battery cables, and checking the PDC connections. That's where I'd look.....if I didnt want to use a voltmeter to check voltage drop at different points.. ( which I would do)
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Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
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