Ok im not sure of thos os 9n the right place or not so if it is not my apologies . Here os my problem I have a 94 dakota 3.9 motor and at forst my temp guage wasnt reading at all so i looked under the hood and say that the single wire sensor was broke so I changed the single wire sensor first and to my amazement my guage worked . But it read max hot all the time will changing my two wire sensor under I think every one is saying under the ac compressor . Will that fix my problem . O and I just bought this truck 132.000 miles and the water pump and the radiator was just changed before I bought it if that means anything please helpppppp

 

The single wire sensor is for the gauge, the 2 wire sensor is for the PCM. So the gauge is reading high at all times even when the engine is cold and it wasn't working at all before the sensor swap, then the new sensor is bad or a wiring problem.

 

I think you are saying that your gauge didn't work at all, then you changed the sensor, and it is now reading full hot all the time... correct? If that is the case then your wire (from the single wire sensor) is grounding out somewhere.