it hasnt been working since i got the darn thing. its a 1990 Jeep yj with the 4.2L engine in it. The only reason im concerned about it is i think it might be running a little warm. Anyone know where they gauge measures from?

I don't know the 4.2 as well as the 4.0, but, assuming it's the same, it's on the water neck at the very front of the motor where the heater hoses and radiator hoses all enter the motor.

Had problems like this and it turned out to be in the gauge cluster.
Remove and clean connector pins and connector receiver (scotchbrite)
Dismount gauge and clean contacts there also.

Make sure wire is connected to sensor first.
Clean terminal at sensor,make sure wire terminal is tight on sensor.
Inspect wire for damage.

On some of the 4.2 the intake manifold has a water jacket that runs through it and the sending unit is on the manifold if not on the t-stat housing.