Mechanical water temp gauge reading wrong in thermostat housing

[drunkenmonke]

Hi, I recently installed an autometer autogage mechanical temp gauge in my 88 4.0. I went out and bought the newer HO thermostat housing with the threaded port and installed the sensor into it with just one brass fitting other than the sensor itself. I had to use one more fitting because the sender would not tighten and seal fully by itself.  I went this route because a mechanical sender would not fit in the other place toward the back of the motor. The gauge never reads over over 130-140 degrees and I confirmed this by shooting a heat gun at the housing itself. When I shoot the heat gun at other parts of the motor It reads over 200. All coolant has been flushed with all new hoses and thermostat. The heater core is flushed as well. Is this just a bad place for the sensor or could it be that the sender is sticking too far out of the coolant to give a good reading? Any help would be appreciated since I still have the idiot light gauge cluster and have no idea what temp my motor is running at. Thanks.

[Strokermjcomanche]

The sender is too far away from the coolant . A full cluster swap is easy to do and a better option IMO .

[HOrnbrod]

^^^ This. The temperature sensor probe has to be immersed in the coolant to read correctly. Using an inline radiator hose sensor adapter is one solution.