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Unread 08-08-2013, 11:52 AM   #1
Registered User
2001 WJ 
Join Date: Feb 2010
Location: usa
Posts: 126
Voltage regulator issue solved

I wanted to throw this out there because I saw a lot of threads about voltage issues, battery drains and spikes. My 2003 4.0 WJ was fine, then 2 days ago I started it up went to the store and when I came out she was beyond dead. Not even enough power to honk the horn. I got a jump and had to hold the gas to keep it started. Finally it idles ok so I go home. I'm sitting in the driveway idling it and then the battery gauge starts to go fluctuate going from normal halfway down to 1/4 then up to 3/4. Suddenly I get a loud pop from the speakers and the dash lights start flickering on and off. I shut it off and thinking it was an alternator issue I changed the alternator. After I finished I jumped it again and for about 1 minute it seems ok, then goes haywire again. I hightailed it to my parents house because I have another identical WJ sitting there. I get to my parents and shut it off and again not even enough for the horn to beep. Now I'm thinking voltage regulator in the pcm is fried, but for ****s n giggles I tested the battery with a multimeter. 12.77V but I can't even beep the horn. I ran to the store got a new battery and all is fine now. Just thought that was weird, I've never seen a battery try to take out the entire electrical system before like that, especially when it was fine the day before. Just wanted to share that because I see a lot of similar posts and some people are suggesting that the voltage regulators in the pcm are bad. I just want to strongly urge people to try to swap the battery before condemning the pcm or alternator. Pull a battery out of a friend's car to test it if you don't want to waste money trying things. I assume mine had a bad cell or something.

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Unread 08-08-2013, 03:53 PM   #2
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2004 WJ 
Join Date: Jul 2006
Location: Stouchsburg, PA
Posts: 8,165
The 04 limited my mother in law has had the volt needle moving back and forth 1/16 inch all the time.

1 month later the battery was dead. New battery and a steady volt needle.
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Unread 08-08-2013, 06:04 PM   #3
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1999 WJ 
Join Date: Dec 2010
Location: bridgewater, nj
Posts: 739
What you described is a fairly common issue with the WJ when the battery is going. There are dozens of posts on this forum just like yours. The electrical system goes wonky when battery is going bad.
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Unread 08-08-2013, 06:16 PM   #4
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2002 WJ 
Join Date: Jan 2012
Location: Orange county, CA
Posts: 1,012
Yeah..that's odd because at 12.7 resting that's a fully charged battery.
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