[Oldsguy]

Greg,
Welcome to our site. You say "heat gauge" I think you mean engine temperature guage right? What Larry said about checking the fuse panel is the first thing to do. It sure sounds like you have some intermittent grounds that are causing your gauges to act up though. If you have a good fuse (probably labeled "instruments"), then I would next start looking for a wire grounding out like Larry said. Your engine termperature sensor is usually on the driver's side of the intake manifold in the front. It is mounted vertically in the water jacket crossover of the intake manifold next to cylinder #1. To check your fuel gauge I would start back at the fuel tank first and find the wire that runs from the top of the tank up the passenger side frame-rail to the firewall. Inspect both those sending wires and look for bare spots that could provide shorts to ground.