So it started out when I got a check gauge light and I noticed the voltage was dropping. I drove by oriellys and they tested the alternator, it tested bad. So I replaced it the next morning. I had the battery on the charger overnight and put it back in after I changed the alternator. It started and ran fine for a little while. After a while the check gauges light came on again, same thing. So I took the battery and alternator off and took them both to oriellys. I thought maybe they had sold me a bad alternator. Well they tested both and the alternator was fine but the battery tested bad. So I took the battery out of my dads truck and put it on the truck until I could get a new battery the next day. Well it seemed fine for a day or so but when I left work that next day, same thing, check gauges light came on and the volts dropped. Eventually the lights became very dim. So I've been asking around and I've been told it could be the computer. I was thinking if it was the computer that it would be showing funky codes and having other problems, but hell if I know. I was just wondering if anybody has had this problem or has any advice. Thanks so much!

 

Sorry meant to specify that it's a 99 half ton with a 5.2, 4wd.

 

Voltage regulator is part of the PCM, seems yours has failed. That won't set any codes, except for maybe whining about low voltage...... If alt, and battery test good, PCM is all that's left.

 

That's a stupid design. Doesn't GM put the regulator on the back of the alt?

 

That's what I figured. Yeah I've researched it and it is a very crappy design. Thanks!

 

Yep, I thought it was a silly idea too....... I don't pretend to understand the reasoning behind that particular decision, but, it's getting to the point that the computers in vehicles control EVERYTHING, even the heater.... Won't be long, and you will need the computers permission to roll down your window.

 

A failed regulator in the PCM won't throw any codes until the battery is discharged to the point of confusing the works. If it's a failed regulator, you can just swap in a mechanical regulator from a late 60's/early 70's Chrysler V-8. There are instructions all over the web for that. It's cheap and easy enough.

 

Could it possibly be a bad wire or a bad ground?

 

Anything is possible. Would have to do some checking to be sure.

 

Did you check the alternator fuse? The one in the engine compartment. You should have done this before anything!