96 GC- amp gauge goes dead intermittently-computer?

[muddyyj95]

Ive got a 96 GC (4.0 six/auto/air/4x4/207,000 mi) that the amp gauge has been going down to 1/4, then the check gauges light comes on and it goes all the way down. After it started doing that, I pulled the battery cable, and took the alternator over to Autozone, and they said it was good, and that it might be the voltage regulator - that's controlled by the computer. So, I took it home, put it back together, hooked the battery up, and it was fine for almost 75 miles till the very end, then it did it again. When I shut it off at the store, and turned it on again, it was fine for the 20 miles home.

Maybe I should mention that I (had) to drive it through 18 inches of water about 6-8 weeks ago, and the same thing happened, but didn't happen again until this passed Tuesday morning. what's the consensus? Computer?