Temp gauge was running around 150 and I hadn't looked at the thermostat since I bought the car so I decided to install a new STANT 195 for winter. Installed the new 195 and the gauge was still reading 150. Thought I must have a bad engine coolant sensor so I head on down to the parts counter and grab a new one. Installed new sensor and gauge still shows 150.
Tonight I removed radiator cap and let the engine idle about 10 minutes to warm everything up and the electric fans engage and run about 45 seconds and shortly after the fans start I can look in the radiator and see that the thermostat has opened and water is pumping through the core. Outside air temp is about 50 degrees. Thermostat cycles normally. Gauge in dash reads 145-150 as the 195 degree thermostat opens and closes.
I guess the next step is to get a scan tool on it and see if the sensor is sending a reasonable value to the PCM and try to determine if I have a bogus gauge in the dash. Oil pres, fuel gauge, volt meter all seem good. What else should I look for?