So I know there's a ton of these questions on here, and I've spent the last hour combing through them, but none that I've found have the answer to my question or my specific problem.

For starters: 1992 F-150, 4.9L I6, M50D 5-speed manual, 4x4.

So out of the blue on my drive home last night, my voltage gauge started reading below the N on normal. My headlights dimmed, my blower got very weak on the highest setting, etc. No missfires or anything and no loss of power, so I just kept driving home. When I pulled into the driveway and stopped, I just stared for a while at my voltage gauge. Seemingly at random, it picked back up to reading perfectly normal and my lights and blower went back to full steam. So I parked it for the night. This morning, it starts up and runs like a dream (as usual) but my voltage gauge is back down below the N. I drive around with the heat on, and almost every 10 minutes it the gauge will read normal, the blower picks up, and 60 seconds later, it's gone again. It has nothing to do with what gear I'm in, how fast I'm going, etc. What could this be?

PS. Battery is three years old, alternator is 5 months old, connections are solidly connected with a touch of dielectric grease.

 

Bad connection, or voltage regulator.

 

X2....only I'd get yer alt checked too. Just cause it's new doesnt mean it's good. Ice bought new rebuilt alts that were bad from the start.

 

If it were a voltage regulator, wouldn't that just mean it would go too high? Not cap at normal but die down low at random?

I insisted on new, no rebuilt for me.

 

The alternator is internally regulated, if the regulator is bad the alternator is bad. Too low, too high, it controls these things.

 

Bear with me on this, but that means I've essentially got to swap the alternator again, correct? Provided it's not bad connections?

 

Ehh I'd still get it checked. Really to me it's the alt. Usually it's diodes that go bad. The regulator is in the alt anyway so to check anything it'll have to come off. Check yer battery cables, look for corrosion.

 

They can test it with it still on the truck.

 

"They?" Any reason "I" can't do it?

 

Yes, you too.