I have an 01 A4 1.8T. The thermostat gauge sits at cold, intermittently, and I get heat out of the vents. I was thinking that it could be a sending unit or gauge. I would like to test the senors/sending units but dont know were they are at. Can anyone help me...Thanks.

 

How much heat do you get? Good heat = bad coolant temperature sensor. Weak heat = bad thermostat. Or if the gauge jumps around a lot then that also means a bad sensor.

 

its good heat...were is the coolant sensor????