I took my truck to the dealer, 1st mistake, for tranny fluid and coolant change. When I got it back, they told me they did the multipoint inspection. Its a 2004 silverado 2500LD.

Was driving around and noticed the voltage gauge drop from 14 to 12, and lights flicker. Then the gauge works fine. Worked fine for a couple days, then did it again. Replaced the alternator with an Autozone one. Everything worked great for 900 mile trip. The truck was parked for 3 weeks, and got in and started right up. Lights flickered and voltage dropped to 12. Did this for about 5 minutes, then came up to 14. Changed the battery with my spare, and still does it on occasion. Its not all the time, but some times it does. Turned things off, and on when it does it. Nothing changes. It is not causing a voltage malfunction light, but I see it on the gauge and lights.

Anyone got any ideas?

 

Big 3 wire kit.

common the the trailblazer SS. Weak charging system in general. Larger ground wires/power wires.

Just a guess.