If your "BATTERY" light is on while your engine is running, then the problem is usually either the alternator or the voltage regulator. This simple test will help you figure out which, without having to remove anything. It applies to 60's vintage GM cars using a points-style voltage regulator. Here is a picture of that type of regulator.
 "click for bigger photo")
Points-style voltage regulator with terminals identified
With the engine running, connect the negative lead of your voltmeter to ground (or the negative terminal on the battery) and the positive lead to the #2 terminal of the voltage regulator. If the #2 terminal is hard to get a good reading from, you can instead measure the voltage on the black wire that is in the 2-wire connector on the back of the alternator.
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back of alternator
If the voltage is under 5 volts, then the alternator is bad. (Or the belt tension is way too loose.)
If the voltage is over 5 volts, the problem is either the regulator or the wire harness between the regulator and the starter solenoid. Most likely it is the regulator. Since the regulator is so easy to remove, you should just pull it and take it in to be tested.
Anonymous on Jul 21, 2008 at 02:04 p.m. said:
"Framer test" While still running put screwdriver on back of alternator (watch out not to ground out terminals). If alt. is working it will stick, no sticky no worky.Get home, get it fixed
