2012 Tahoe-Lights get brighter and dimmer

[ftwflh]

This is most noticeable with the dome light.With engine running and parked the lights fluctuate from bight to dimmer. The engine seems to gain and loose a few rpms when this is going on too.
I have noticed the volt meter going up a little more than normal.Like up to a little of 15v. Truck runs good and it doesnt discharge or fail to start.
I do have my second AutoZone alternator on it.Last one quit charging a couple months.

 

[wjburken]

This is most noticeable with the dome light.With engine running and parked the lights fluctuate from bight to dimmer. The engine seems to gain and loose a few rpms when this is going on too.
I have noticed the volt meter going up a little more than normal.Like up to a little of 15v. Truck runs good and it doesnt discharge or fail to start.
I do have my second AutoZone alternator on it.Last one quit charging a couple months.

Do you know if the compressor on your air conditioner is kicking in when this happens?

Might put a volt meter across your alternator to see what's going on there as well.

 

[OR VietVet]

Sounds like the internal voltage regulator is having a problem. I am assuming, I hate to do that, that the alternator is a reman or rebuilt. Lots of times when this is done the parts that check good when they start the rebuild/reman process, are reused. Check all ground wires under the hood and along the frame. Lots of threads here about "ghost" electrical problems.

 

[Doubeleive]

Something like this is common with a poor ground, I would check your battery cables and body grounds, the cables on these trucks are known to corrode from the inside.
also don't depend on the volt meter in the cluster to show the actual voltage, check it at the battery, you might be getting 15v but low amperage due to poor ground which would cause the dimming effect.

 

[Seamus]

My 2013 does this also. 100% stock, in near perfect stock condition. Original alternator. I had already checked all my grounds and they are perfect. This truck spent its entire life in Florida and has no corrosion at all. I notice it when the AC compressor kicks on or the fans. There have been issues with many finding the cables are bad from the inside even though looking good upon inspection. I intend to replace all the power wires with 2 gauge. On youtube they call it the BIG three. Battery to starter, to fuse box, to alternator. Many videos on it. My 2017 Denali did not do it, but these older ones seem to have it as a design flaw. It annoys me, but I have not had one issue with the truck regarding it.

 

[BG1988]

My 2013 does this also. 100% stock, in near perfect stock condition. Original alternator. I had already checked all my grounds and they are perfect. This truck spent its entire life in Florida and has no corrosion at all. I notice it when the AC compressor kicks on or the fans. There have been issues with many finding the cables are bad from the inside even though looking good upon inspection. I intend to replace all the power wires with 2 gauge. On youtube they call it the BIG three. Battery to starter, to fuse box, to alternator. Many videos on it. My 2017 Denali did not do it, but these older ones seem to have it as a design flaw. It annoys me, but I have not had one issue with the truck regarding it.

ground wire
open all 4 windows at the same time . do the lights dim a lot?


I'm Not buying that it's from "Florida" and has no corrosion at all.


when the lights dim you have some impedance Ω




mine is a California car it has only rained about a dozen times since 2008

this: could you say these are in good condition.

looks like they cut corners and used aluminium cables i'm pretty sure its not tinned copper i don't see any copper blue corrosion

View attachment 237090

 

[ftwflh]

Sounds like the internal voltage regulator is having a problem. I am assuming, I hate to do that, that the alternator is a reman or rebuilt. Lots of times when this is done the parts that check good when they start the rebuild/reman process, are reused. Check all ground wires under the hood and along the frame. Lots of threads here about "ghost" electrical problems.

This was the problem.AZ reman went bad again.3rd one to go bad.They gave me a NEW factory one at no cost.