With a volt meter check across the battery with the car not running. A good battery will read 12.5 to 12.9 volts. Start the car and read across the battery. it should read above 13.5. I've seen them as high as 14.7. The voltage regulator is nothing more than a relay that turns off the altenator to the battery so it will not over charge. i don't have a fool proof method to check the regulator. Anybody else got any good methods for that?

 

what? I am totally confused...I thought the regulator just keeps spikes from damaging system...but don't know

 

The regulator limits output from the alternator, a non internally regulated alternator can make alot of voltage. You can check the alternator by the pin in the back that connects to the wiring, check the regulator by checking voltage after the regulator. One side will be the same as the alternator, the other side wont. Its been a while since I worked on external regulators, so I cant tell you what side it is on the thing.

You do need over 13 volts to charge the battery, and if its barely over 13V, then it wont be when you turn on lights, stereo, wipers, fans, etc...