my alt went bad and i went to get a new pne and they have two kinds a 120amp and a 140amp what one came on a 94 z/28. thanks

 

I think it was the 140. But even if I'm wrong id get the 140 anyhow

 

ok thanks. now i know in old cars u can have the car running and take off the + side and if the car keeps running the alt is good and if it dies its bad. can u do that with these. if not how can u test them.

 

you can go to just about any autoparts store (autozone, checkers, advance auto parts). And they can test it for you.

 

This is not a good idea as it can damage the voltage regulator. Best way is to either use a digital voltmeter to check voltage with everything you can think of turned on (looking for 13.5-14.4 volts), or remove it and have a parts store check it. I would do the later first.