Truck Repair: Gages, chevy silverado, 2003 chevy silverado

Question
I have a 2003 Chevy Silverado 3/4 ton PU truck. My gas guage started acting up, first it pegged out past full, then it seemed to work. Then it dropped to Empty and hasn't moved since. Also at the same time the voltage gage pegged out past 19 volts. I checked the voltage and it was 14.2 with the engine running. Any suggestions on what to check, Thanks

Answer
I would check for a bad ground.
Make sure there is a ground wire connected from the engine to the firewall, clean and tight.\
Then find the ground terminal under the dash, probably above the parking brake pedal, and make sure all the wires are tight.
May need to wiggle the connector to the instrument cluster also.

Van