Gm alt question (voltage regulator)

[Strange]

so i have the 80s gm alt (10si 12si) one of those kind with the white 2 port plug on it.

Its wired up correct (not converted to "1 wire")
lug to battery, the one plug to idiot light, and other to 12v source for excite

for the last few days everything has been fine, but today i saw the gauges start to jiggle a bit. Then a little bit later it got worse.

The volt gauge would peg, then all the gauges would go crazy for a sec, then speedo would die, radio turns off, and the digital read out in the truck goes berzerk. then 10 seconds later everything will be back to normal.

does this sound like a voltage regulator intermittently being an asshole?
battery is good, and of course when i tested the alt it passed....damnit

[the_experience3006]

More information on the truck would help identify what kind of dash arrangement you're dealing with. If it's a completely digital dash I'd be far less inclined to believe it is an alternator problem than if you have an old mechanical dash.

[acprokeith]

Charge the battery up and disconnect the Alt. If it continues its not the Alt.

[the_experience3006]

Disconnecting the alternator is fine if he doesn't have any electronic modules in the truck. The description of the truck doesn't really tell us that for sure. TBI era electronics are pretty robust, but the digital dashes are not and voltage spikes could really wreck his day. How about a simple test with a mechanical voltage gauge? You can probably get one for $5 at harbor freight and wire it up quick to keep an eye on system voltage when it happens.