Hello all...

The truck in question is a 1994 Chevrolet C1500 W/T with the 4.3L V6
engine. Its factory alternator gave up the ghost...it would charge at
highway speed or with the engine revved up but never at idle. The
battery is not quite a year old, and it tested good at the time.

I put a remanufactured alternator on there and for the first few
weeks, things were fine. Just last night, however, the alternator not
only stopped charging, but also appeared to be putting a heavy load on
the electrical system. The voltage gauge dropped into the red and the
lights got very dim. Fortunately, it never quit running.

Upon getting it home, I discovered that the alternator appears to work
fine at idle. Rev it up and charging falters or stops entirely. The
battery still seems to be in excellent shape (all cells test fully
charged with a specific gravity tester even after letting the truck
rest overnight), so I suspect the new alternator has gone bad as well.

Any thoughts? I've never seen one fail like that before.