I have noticed that my headlights and dash lights are pulsing at idle. They brighten and then dim. I had the charging system and battery tested and they checked out OK.

Thinking I may have a ground problem I added a ground from engine to frame and that did nothing.

Any ideas on this problem?

Thanks,
Tim

 

This is your 07 Tahoe? What's the alt gauge doing at idle as they dim?

 

Yes, it is my 07 Tahoe sorry for not stating that in the first place.

The alt gauge will sit at 14 or a little above at idle and doesn't fluctuate much. When going at highway speeds it sometimes drops to around 12.

 

Interesting - I was expecting you to tell me the gauge fluctuated below twelve as the dimming happened.