Thermostat or Thermostat and Water Pump

[mikesz]

as mentioned above there is a sensor on top of the engine passenger side. I replaced mine cost about $35, also there is the passenger side engine vent fan behind the vent, mine was binding I got a used one for about $50. Could just be low coolant level, I have found just a slight decrease sets it off.

[911monty]

+1 on the coolant level. The temp gauge does not work in steam or air, needs to be in water. Coincidentally the heater core will also not put out any heat without water circulating. Be sure to use the proper coolant and purge the system if it is low.