New to the forum so if this thread doesn't belong here l apologize. I have a 2001 express 1500 4.3L V6. Monday it died on me driving to work,mad l suspected it to be the alternator. I replaced the alternator & battery with no luck. The van would crank but no start,turns out it was the fuel pump. I replaced the fuel pump and the van started right up and drives fine,however l noticed that the volt gauge bounces when a load is put on it. When at idle l can turn on the A/C,lights,radio and nothing happens. If l start driving with all the loads on, the volt gauge starts bouncing 14-18 volts back an forth continuously. I have checked the battery not running (12.53volts) and running with the loads on (14.35volts). I have checked all fuses,grounds etc. I had auto zone test the battery & alternator and they said they were both good. My question is,is it possible to have a bad voltage regulator even if the alternator is testing good? could the fusible link have anything to do with this. It is not showing symptoms of a bad voltage regulator (ex: lights flickering,loss of power or acceleration) Any tips or things l should check would be helpful. TlA!

 

Alternator should be internally regulated. Not unusual for the gauge to fail or be inaccurate.

Of course if you still have your old alternator you could swap it back in and see if that solves the issue. But I would wiggle the connections first and make sure all is tight.