Headlights and interior lights dimming back and forth quickly

[weo1209]

03 Yukon SLT. Noticed over the holidays as I was driving my interior lights (dash, overhead lights) etc would dim and flash back and forth from dark to bright again. I looked out to my headlights and noticed the same thing that they were dimming back and forth really quickly. I had battery checked out, ended up being bad, got it replaced for free (warranty) and had the alternator checked and looked at, and everything seemed fine. A few more days passed and now its doing it non-stop. Could it be a fuse? Bad battery cables?

Tried searching forum about it, couldnt really find anything relevant. Any help would be appreciated.

 

[yates ™]

I would say something in wiring. Is anything else effected or just lights? Does the voltage gauge show a voltage drop?

 

[weo1209]

No change is voltage or anything that I notice, like I said, I had the alternator checked out once the new battery was installed, no probs there.

---------- Post added at 04:57 PM ---------- Previous post was at 04:46 PM ----------

Nothing else is different in the car by the way, stereo is fine, and I must add it does it more when I am driving rather than stopped at a light or something.

 

[yates ™]

I am betting a loose wire, shorted wire or a bad ground somewhere especially if there is no noticeable voltage drop. I didn't think there was a common distribution block for all the lights but if they are all that is effected then there has to be one.

 

[OmarR]

The main ground for the headlamps are behind the drivers side foglamp on the chassis. For the interior lights, if you remove the interior A-pillars on both sides, you will see a ground at the base of each one. It doesn't cost anything to tighten the grounds, but since you have lights dimming that don't share the same ground, I doubt it's the grounds.

The interior lights and dash lights all get power thru something called the bus bar, which controls dimming. Unfortunately, that is internal to the BCM, so that would mean a new BCM.

However, your headlights are not apart of the bus bar, and you report that they are also dimming. You already changed the battery. If it were me, I would also change out the alternator (even though it checks out ok on a machine at an auto parts store) and even take the opportunity to upgrade to a 145a or 200a alternator.

 

[Pachanga02]

i had the same problem on my 02 denali and i changed my alternator and battery and it stopped. good luck