Battery Light

OK, Here's a different take on the battery light.....all of the sudden, my battery light came on.....now I have read about others having the light come on at high RPM's. Mine comes on at low RPM's and goes out as the engine speed increases. My idle speed is @800-900 RPM and has been the same before and after the light came on. I have removed and cleaned both positive and negative battery terminals and connections. The battery reads @12.8 volts with the engine off and @14.2 volts with the engine running at idle. It changes only a few 10ths of a volt when I rev the engine. Can bad brushes cause the opposite problem everyone else seems to have with the battery light?

What kind of shape is the belt in? If it is worn out or glazed you will get what you describe. From your description the alternator isn't putting out enough juice at idle to get the light to go out. Your voltage readings are acccurate, but the unit may not be putting out enough amperage to make the light go out. Cleaning the battery terminals is a good thing to start with. The voltage regulator (internal) could be causing the light or the brushes are too worn for the springs to hold them against the armature. If the alternator has over 100k miles I would replace it along with a new belt. It's easy enough to do yourself and is about $125 for unit and belt. Dealer gets about $550 so do it yourself. Dave

hehe.....the connections on the alternator itself were loose. The clips that hold the connectors to the connection are broken, so they work themselves loose.....it's amazing what you find sometimes....

That's great. First things first. Appreciate you letting us know what the outcome was. It will help somebody with the same problem.

the reason the rpms effect the light is because of belt slippage. i replaced my tensioner about 3k mi ago and have had no issues so far