when i rev it out to about 4000 rpm or more the battery light comes on. i had noticed at night that the lights would dim. doesnt happen any other time that i have noticed. i'm guessing either the battery or altinator, but why? i only have just over 51xxx miles. i have added a light in the bed and foglights, would either of these cause this problem? Thanks!

 

Sounds like the voltage regulator. When the battery light comes on, it means that the rotor currents are being supplied by the battery, not the alternator. Unfortunately, if I recall correctly, the regulator is internal to the alternator, and in today's world of "swap the whole unit", you'll prolly have to replace the alternator.

 

thats what i was thinking. got out the voltmeter and measured last nite, voltage drops from 14.xx to 12.xx when it gets to about 4xxx rpm. going to call the dealer today. thanks

 

I had similar symptoms once. It took forever to find it. I hope your solution is this simple.

Make sure the belt that drives the alternator is tight. Not too tight or you will wreck the bearings. If you can spin the alternator by hand without serious grunting, it is too loose.

If it has been loose for a few months, a V belt can cut and wear the pulley. You can't always tell by inspection but a new belt and alternator pulley is required to make things right after they get worn that way.