The temp gauge on my 1993 c1500 recently quit working. The check gauge test at start up indicates that the guage is working, but, while the engine is running, the gauge never moves above zero. Thermostat is less than 2 years old and the engine warms normally, but the gauge doesn't move. Also nothing changed when I recently installed a new temp sensor. Has anyone had a similar problem? Should I try replacing the coolant sensor?