Just bought an old fleet truck for my son to use as a beater with a heater. 2002 1500 two wheel drive with the 4.8 engine and automatic transmission. Back when these were new my construction company would have a half dozen of these rolling around and I was very impressed with how they held up. This unit appears to be in decent condition - but occasionally the "BATTERY" light pops on and the 4 gauges (gas, oil, volts ,temp) will start wavering back and fourth from max to min. After about 30 seconds or so the BATTERY light shuts off and everything returns to normal. Is this common? Do I have a ground or alternator issue? Gauge cluster issue?

 

It sounds like you have a ground issue.

I would go to https://lemon-manuals.la/ and look up the service manual for the truck and find the power and grounds location information and then dig in, undo the current grounds, clean and shine up the surfaces, and then refasten the grounds and hopefully, most of these electrical gremlins will disappear.

Good Luck!