Sorry but I'm thrown for a loop.

1995 Chevy 1/2 ton 350.

Noticed the dash battery light was on and the volt meter was showing 11 volts. Pulled the alternator, had it tested and failed.
Put a rebuilt one on. A little while later, I notice the battery light on, and the volt meter showing 12 volts. With the engine running (revved it to make sure the alternator was excited), I measure 11.74 volts at the battery, and at the alternator. Take the alternator off and it tested bad.

I put on the second rebuilt alternator and start the truck, no battery light and 14 volts. 2 blocks away and the battery light comes on and 12 volts.

What is going on here? I don't think it's the "shouldn't get a rebuilt alternator" syndrum. What do I need to check?? Is something pulling that much current to smoke the diodes that fast?

Have you had your battery load tested? Sometimes a partially shorted battery can pop alternators.

Thanks for the idea John. I'll try that before I install another alternator from elsewhere.