I have the same problem as Mustang11, but when I accelerate the gauge goes down, then back to real high. Think it's the gauge going out. The car runs fine, but want to be sure. Check the water level every time before I run it, and only twice has it been a little low.
Same thing is going on with my oil gauge, locked at zero, used to stay in the middle while I was driving and goes to zero at a stop.
Planning on switching to better gauges, anything else to pay attention to/replace while I'm already in there? Going to replace the sending unit, but any other hints as what to look for?