Approx 6 months ago I had this problem and was able to wiggle wires re-seat fuses etc... and the problem was gone. Now it is back but wiggling wires re-seating fuses doesn't resolve the issue. This time it appears to be the voltage regulator due to headlights dim and get bright battery light comes and goes right along with the headlights dimming etc... Is the voltage regulator portion of the alternator separate from the alternator? Can I replace just the voltage regulator?

 

The regulator is built into the back of the alternator. Is the on-off battery light related to engine rpm?

 

Yes it is, what next?

 

Before throwing parts at this problem, consider running this puppy by your favorite auto parts store & ask for their electrical system test guru to perform a no cost, in vehicle, under load electrical system check up, with their electrical system tester, get a print out & report back with the test results.

 

I will stop by Advanced Auto on way home from work today and have them check it out for me and report the results later today.
From the indications thus far does it look like the voltage regulator portion of the alternator?

 

had Advanced Auto check the charging system and found that the alternator was not charging at all. So drove home and and checked voltage when RPMs up and then battery was charging. Long story short the alternator is not charging.

 

How many miles on this alternator??? If many miles, with the charging coming & going, could be worn slip ring brushes.

 

Maybe 20K miles, had it replaced about 1 year ago. That being said I asked the shop that replaced it and they said it is covered except for labor. Hopefully it was just a bad alternator. Thanks - Caldwell

 

Since the alternator was recently replaced & you've been having problems with it for some time & a previous wire & fuse wiggle test woke things up for a while, have a close look at, or better yet use your multi-meter to measure the B+ & B- connections between the engine & battery for under load voltage drop.
If your going to install it, have them bench test the replacement before you leave the shop with it.
Was this one a New, or Reman alternator? If new, make sure the replacement is a new one too & let us know how it goes.