Several years ago I had a problem with my temp gauge and found the wire terminals on the back of the gauge very corroded and a bit loose giving intermittent high resistance. I removed the screws and cleaned the terminals with 600 grit sand paper and reinstalled them and problem solved. NOTE if you try this, only take out ONE screw at a time, if you remove them all at once, the gauge will get loose and you might have to disassemble the instrument panel to reattach everything. Ask me how I know........