When a parts store puts an alternator on a tester, can they tell what the output (in amps) is for that alternator? Or do they just say bad or good? I have a couple of alternators on the shelf and am curious about the amp ratings.

Good testers measure amps output and voltage.

Ron

Alternators will deliver much more then they are rated. It depend on the amount of heat the Alternators dissipates. The less heat or more effiecient (depending what RPM your spinning) the alternators delivers, the higher the rating. Alternators can regulate from 14.5 down to 13.8 Volts depending what load you applied. You just adjust the amount of current until the voltage drops below 13.8 volts at what RPM and heat it will deliver.

When a parts store puts an alternator on a tester, can they tell what the output (in amps) is for that alternator? Or do they just say bad or good? I have a couple of alternators on the shelf and am curious about the amp ratings.

Are they original alternators or rebuilt alternators. 10DN (externally regulated) 10si, 12si, CS130 (internally regulated) or ??? Post the numbers off the alternators (if original) and maybe someone can tell you the original app and amperage for them.

I had a couple of 10dn alternators of questionable performance (I had never used them) that I took down to the local parts store for testing. The test showed the Volts and the Amps.

Thanks, elsolo. I have some old cats and dogs of various types. Old enough to be rebuilt probably so the number stamped on them would be meaningless. That is why I was interested in some type of test.