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Old 02-25-2014, 09:12 PM   #1
Join Date: Feb 2014
Posts: 1
kcfan491 is on a distinguished road
Need Help. Alternator, or ECM

I have a 95 jeep wrangler sahara 4.0l automatic. It has a new battery, that has been going dead every so often. I pulled the alternator and took it to O'Reilly's. They tested it and said it was fine. I cleaned up the connections, charged the battery put the alternator back in, and drove it for a week.

Then battery went dead again, so I jump started it and drove back to O'reilly's. They tested the alternator in the jeep and it said "bad diode, low output". The jeep ran for about 20 minutes while I was having it tested, and on my way home the headlights were dying on me. I figured the alternator had finally went out. I pulled it back out and had them test it again. It still shows as good. The parts guy said that my alternator is controlled by the computer, and that it must be bad.

I'm considering 3 possibilities at this point.

1. The alternator is bad/inconsistent, and the O'reilly's tester sucks.
2. I need an ECM
3. I have a bad connection somewhere I haven't thought of

I found an ECM on amazon for $220, and you send them your vin and they program it for you. Is it hard to replace? Does the Computer even control the alternator? Am I missing something?

Thanks for taking the time to read this, any info or suggestions are greatly appreciated?
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Old 02-26-2014, 08:06 AM   #2
harleydragon's Avatar
Join Date: Jul 2012
Location: south georgia
Posts: 3,939
harleydragon is on a distinguished road
yes,your alternator is regulated by the computer..replace computer or swap to a chevy alternator with internal regulator
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alternator , battery , ecm , wrangler

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