results to share w/ folks.... Car: 1995 Saturn SL1 SOHC. Symptom: Temperature gauge reads temperature but engine is running cool. Temp Gauge below typical running temperature. About 2 minutes after car starts running the radiator fan starts and runs until ignition is off. Season is summer; environmental temp is about 27 deg Celsius. Typical drive is 60 minutes duration. Engine is not overheating. No leaks in coolant system/hoses, reservoir level is good. Coolant mix is ethylene-glycol coolant with distilled water in a 70:30 ratio. My thoughts: From reading my Haynes manual, it appears the thermostat is stuck open. However it appeared to be also a sensor problem as the fan is running on.... Troubleshooting: 1. Wiring harness ok 2. checked the PCM/CCC/computer trouble codes = code 14 only. Temp sensor high temp. 3. I replaced the engine coolant temp sensor and viola the problem is resolved. The new sensor (Niehoff) has a brass body at the sensor tip. The original was a plastic body and it appeared to have a small crack in the body. I hear there's alot of trouble with these. Anyway lookup a great how-to-fix video on Youtube ... very well done by Richard ("richpin06a") [MEDIA=youtube]JC0U53w_Htk[/MEDIA] 4. I did not replace the thermostat. Cheers, Roger