Ed,

Those pins and slots often don't make good connections. I'd pull the board ... lightly rub the corrosion off the pins with the eraser of a pencil ... then gently compress the slots so they make tight connections when the board's inserted. Also check to make sure the screws holding the gauge to the main board are tight to assure it's grounded. This may help ... but the little buggers are often hard to get working correctly. You can remove the boards and jump the connections ... instructions on that can be found in the archives. I've had good luck by simply replacing the Temp/Comp boards with a good working piece from the Pick and Pull.
Good luck.