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Discussion Starter #1 (Edited)
Driving to a George Strait concert 100 miles from home I noticed my voltage gauge moving from 14+ volts down below 12 and raising back in the normal range, intermittantly. Speed was steady at 70 mph. This lasted for 15 minutes or more.

Then, the battery light came on and the voltage started slowly falling down into the 12 volt range. Then, the battery light went off and the voltage went up to 14 volts again.

Me and my sweetie stopped at the mall for an hour, got back in the truck and the same problems started again.

What I've noticed is that the lights seem to have steady brightness, no dimming at low rpm or brighter at higher rpm.

Is it alternator brushes, voltage regulator or something else?

I searched the forum but found no other problems that seemed to fit the bill.

Thanks for the help.
 

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Could be a voltage regulator, but I think it is inside of the alternator. are your batteries good?
 

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Check the battery connections... they could be loose.
 

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X2 on the battery connections.
 

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What truck do you have? These alt will shoot up to 14 when there is a demand and then when there is not, they sometimes fall down to 12. Soundsl like some thing is allowing the voltage to drop below where it should be and the light is kicking on. I would have to agree on connections and then probably the regulator, which is in the alt.
 

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Discussion Starter #6
It's an '01 6.6 2500HD 4X4. This thread was moved from LB7 1st gen electronics to here. I guess I posted in the wrong location. Live and learn. Thanks to everyone for your help.

This morning I jumped the truck and tested the alternator with a voltmeter. Zero output. My intuition tells me that the voltage regulator is the problem as I understand the regulator is built into the alternator.

If I'd had the time I would have replaced the brushes and regulator, but instead I picked up a remanufactured alternator and it fixed the problem.

Thanks again, folks. This forum rocks and has saved my $hundreds$ and fed my brain. You guys and gals ROCK!
 

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The light doesnt kick on at low voltage level. When the alt stops outputting all together then the light come on. Probly the contacts on the regulator.
 

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Discussion Starter #8
floriduramax1;1568260; said:
The light doesnt kick on at low voltage level. When the alt stops outputting all together then the light come on. Probly the contacts on the regulator.
Good info. Good to know. Thanks.
 

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My LBZ did it for a short time and the Alt. crapped out. Dealer warrantied it. Will go to duals when the warranty runs out, possibly sooner.
 

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Hmmm. i'm reading this intently. tonight on my way to hockey the same thing happened. 14 to 12 to 14 to12, 11, 10.... and the battery light comes on "batteries not charging".

what i'm reading here is, it doesn't matter if it's the alternator or voltage regulator as the result is I will be replacing my alternator?

Was the alternator change and easy DIY?
 

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caswell;1596510; said:
Hmmm. i'm reading this intently. tonight on my way to hockey the same thing happened. 14 to 12 to 14 to12, 11, 10.... and the battery light comes on "batteries not charging".

what i'm reading here is, it doesn't matter if it's the alternator or voltage regulator as the result is I will be replacing my alternator?

Was the alternator change and easy DIY?
It's easy to do. Just unplug wires it top of alternator. Use 10 mm wrench to remove cable in back of alternator. Use large screwdriver or prybar to wiggle alternator out. I also use a deadblow hammer or regular hammer with block of wood to get new alternator in place. Hope this helps you.
 
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