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Hi, I have a 1966 impala and i just replaced intake manifold valve covers and carburator on my 283 engine. Problem is alternator keeps going bad, I have replaced it 3 times. At first my car wanted to turn on then alternator went bad after a few trys and when alternator was replaced it didnt bothered to do anything, alternator just went bad. Can you help please?

Are you sure the alternator is going bad? Meaning it isn’t producing around 14 volts after the engine is started and running? Or is the engine not turning over which would suggest maybe a dead battery?

Im pretty sure, I had the alternator check every time. Good thing I have warranty! Battery is a new optima red top and shows close to 12v on the voltmeter. Car doesnt turn on or turn.

Close to 12VDC is not enough. A fully charged battery will read a little “over” 12V. You need to have the battery checked as well as the alternator. Alternators do not normally fail one after the other if everything else is in good working order. There is something missing here.

IIRC the OEM alternator setup on the Impala had a separate voltage regulator. Have you changed that?

By chance have you gone to an internal regulator replacement alternator. That would open up a new can of worms of getting the wiring correct.

Hope to help.

A low battery wouldnt explain why the alternator goes out every time i turn the key. Can the ignition switch play a role? In the mean time I’ll charge the battery.

Yes, the voltage regulator has been changed.

I assume you are taking these ‘bad’ alternators back to the parts store. Have they tested ‘bad’ on a test machine? When you get the next one, test it on the machine. If that one fails too, retest it and see if it now indicates that it is ‘bad’.

It would be nice to do a postmortem on a ‘bad’ alternator to determine exactly what failed. Most likely it would be a diode which would indicate that the alternator is being called on to provide too much current. BTW is the battery full charged using a power line driven charger?

Also is the alternator (generator) light illuminating ‘on’ the dash just before you crank the engine? Does it go ‘off’ when the engine starts and come back ‘on’ later?

Help us help you.

Luckely i have warranty on the alternator. I’m going to test the alternator before leave the store, just to make sure.
At first, when i was able to crank the engine I did see the light on the dash ‘Generator’. Now it doesn’t do anything as if I have a dead battery but the alternator goes out. I did notice on the last two alternators the ‘R’ terminal were loosen/wobbled. Which weren’t like that out of the box. Does that mean anything?