1998 Windstar - Temp gauge goes to bottom when heater turned on!
I have a 1998 Windstar with 3.8L engine. I replaced the intake gasket last June and the van has run great since. Today I turned the heat on and the gauge slowly drops to the bottom. Turn heat off and it slowly comes up. Changed the thermostat twice with no change. When the heat is off, the temp stays steady all the time even on the highway. Also had an emissions test after the gaskets were replaced with great results! The heat is hot when on. Grounded the temp gauge sensor and it worked fine. What would cause this?