Well i put new negative cables on it and found a couple loose grounds but it didnt change anything, so we can cross that off the list.

 

My '02 started doing this awhile back. I also found battery acid sprayed all over the pass side fender (outside of the hood and down to the wheelwell...paint is screwed there). The ends of my cables seem to be getting corroded really quickly as well. I see about the same voltages you do, and have the disco lights going as well. I think it is probably a diode issue in the alternator, but I haven't changed mine yet. Have you gotten anywhere on yours?

 

The alternator is regulated via the pcm and a corroded case ground or the lack of will often cause erratic charge voltages. A loose pcm connector or failing pcm may also cause similar symptoms!

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quicksilver, ive tried 3 different new alternators so im going to say that isnt my problem. i did change my battery cables and that also did nothing all of my grounds are clean. I'm really at a loss here i've tried everything i can think of. mysetrync; where can i find a new pcm for a reasonable price? Thank you

 

Aes modules, or wire the alternator to regulate externally. Have you hooked a scan tool to the truck? You should look at my post in diesel in distress titled electrical troubleshooting. It would be rare that this pcm circuit would fail and i personally feel a bit more diagnosis is in order but the procedures are a bit long to type on a phone. If you like pm me, ill get up with you monday when i get back to the shop and ill help you out. By case ground i mean pcm case ground, until pcm powers and grounds are checked we cant really call it a failed pcm.

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