Yeah it could have something to do with the regulator setup in the alternator. I'm leaning more towards a ground or faulty connection somewere in the wiring. Have you tried replacing the alternator? I believe you can get the 130 amp off of GMdirect.com for under 200, that's not bad.

 

I had the same problem in my 01. I had aftermarket bulbs in the truck. The stupid expensive high output PIAAs. I took my truck into the dealership due to the headlight dimming feature. They never could find any problems with it. The voltage fluctuation kept blowing the bulbs out. got expensive so I put the regular bulbs back in. The voltage still fluctuated. I am guessing that the problem was a bad voltage regulator in the alternator. Too bad there is no way to change them out without buying a whole new alternator. I have had no problems with my 04 as of yet

 

Has anyone made any progress with this issue. Im sure there are quite a few with this problem including myself. Please Advise

Thanks

 

Have any of you tried taking your alternators into an alternator shop? Someone there should be able to swap out the regulator. I had that same problem after I switched to an aftermarket high output alternator and ended up having the regulator replaced.. The original one was one that was controlled by the PCM, the new one was self-regulated. I had to have the battery light turned off in the tune afterwards because it was not responding correctly to the PCM commands and would trip the battery light, but I have had no fluctuation problems with it since. A new regulator was something like $20 installed. The only thing that shows now is the Generator F-terminal when you scan the PCM, but it doesn't trip the battery light or SES light.

The problem before would happen only when I had the headlights on. The alternator would basically turn off every now and then and the voltage would drop from 14 down to 11.5 or so, then come back. It would do it while driving or while idling in park. When it happened you could hear it because of the Radix fuel pump, the pitch would change when everything dimmed. Really frustrating.