2001 Gmc Sierra Headlight Problem

[kc24clark]

I have a problem, my 2001 GMC has a relatively new battery and alternator, problem is when the headlights are on, they will all of a sudden dim and the amp meter will drop for 1-3 seconds then go back to full charge,this may happen once or 10 times,no pattern to it, any ideas??

[bsibold96]

I have a problem, my 2001 GMC has a relatively new battery and alternator, problem is when the headlights are on, they will all of a sudden dim and the amp meter will drop for 1-3 seconds then go back to full charge,this may happen once or 10 times,no pattern to it, any ideas??

 

It might be a tensioner problem, if that is wore out, it could affect voltage.

[white cloud]

I have a problem, my 2001 GMC has a relatively new battery and alternator, problem is when the headlights are on, they will all of a sudden dim and the amp meter will drop for 1-3 seconds then go back to full charge,this may happen once or 10 times,no pattern to it, any ideas??

 

My alternator died and ate my battery. I replaced both, then got your symptom. New alternator was bad. It did this at 3000+ rpm. The parts place put their tester on it while in the truck, I reved to 3000 and it went from the charge voltage of 14.1 to 12. Showing that I just had battery only power, hence the dim lights.

[ukrkoz]

I had 3 - THREE - bad alternators outta da box same night from Al's Auto Supply here. Fortunately, that craphole is no more around.

So, yeah, good chance is your "new" alternator is nothing but refurbished old one, which you could have done yourself by repalcing brushes, bearings, and capacitor ( think it's about $30 worth of parts).

 

Slipping belt is another option. 2001 sounds about right.