1994 YJ Alternator Voltage to high 15.5! - Jeep Wrangler Forum
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Old 01-18-2013, 12:00 PM   #1
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1994 YJ Alternator Voltage to high 15.5!

What the heck?

I start it, drops to about 11v, fires right up. Skyrockets to almost 16v and holds steady at idle about 15.5v.

I talked to the auto parts store, we pulled out a new alternator and they are externally regulated. Am I right to say they are regulated in the computer?

Its also been 10 degrees and lower for a week or so here. And my computer (ECM) was just replaced in 2009. Its not the capacitors that regulate the fuel pump and freeze up, that is working perfect. Fuel pump comes right on.

Anyone have ideas? Should I replace the old alternator anyways? Maybe install an external voltage regulator and by-pass the computer? It scares me a little running this way. I don't want to damage my cells in the battery and I heard from the parts store it will start popping lights in the dash first. Basically, all the small light bulbs get cooked first...

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Old 01-18-2013, 12:40 PM   #2
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Wanted to add, I am getting;

Code 41: Alternator field control circuit open or shorted

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Old 01-19-2013, 09:19 AM   #3
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last night I tried to start it w/the blower fan on HIGH. I left it on high and the voltage remained steady down at 14v and my light didn't come on.

Anyone run into anything similar?
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Old 01-19-2013, 04:21 PM   #4
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Just noticed mine running higher lately too. i am in IN and its been a bit brisk these past few weeks. Also, my battery was on its last leg...i replaced the battery and my alt voltage is back to normal. id get a starter/alt/battery check at a local auto zone
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Old 01-20-2013, 12:13 PM   #5
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Quote:
Originally Posted by sevenservices View Post
last night I tried to start it w/the blower fan on HIGH. I left it on high and the voltage remained steady down at 14v and my light didn't come on.

Anyone run into anything similar?
Have you checked the voltage coming out of the alt & at the battery? Just to be sure at least... I mean, I'd trust a good voltmeter before a YJ factory gauge lol.
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Old 01-20-2013, 02:10 PM   #6
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I know with my 89 YJ the alternator has an internal regulator. I'd be surprised if that changed on a 94. Don't use the dash gauge as a guide, they're not accurate. Do what JD suggested. In cold weather the dash gauge on my 89 basically registers the same as yours and there is nothing wrong with my alternator.
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Old 07-08-2013, 07:21 AM   #7
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After months of messing w/this it was the alternator causing all my issues. The last straw was that I lost all voltage. I tapped the alternator w/a breaker bar and heard a swooshing sound come from it and the voltage went back to 14v. Probably nasty dirty brushes or sticking brushes...

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