Originally Posted by Don-T
I guess you are running the 4.2 motor. I don't recall a port to install a temperature sensor it. I have a SBC so there is a spare plug in the passenger side head. I bought a switch from Summit Racing that is supposed to close at 200* and open at 185* if I remember correctly. My thermostat is a 195*.
I have an issue with my setup because either the temperature switch is opening early, or there is much difference in temperatures in the motor. The fan starts at about 190*, the thermostat open at 195* and the temperature stays at about 195* so the fan is always running. I ordered a DC Controls controller in the hopes that I can get it set to keep the motor between 195* and 200* with the fan running at a slower speed. I will be measuring the temperature in the fins near the inlet to the radiator so the fan will not start until the thermostat opens and I hope it will regulate the fan speed to keep it as noted above.
Actually that makes sense. If the switch is set to 185 and the thermostat is set to 195 then the fan will never shut off. Probably would be better to have a switch that turns off at 195 and on at 200. One problem with that though is that they are not that exact, switches can vary by 5-10 degrees.
Having said all that it still comes back to what seems like the better option of measuring the radiator temp. I am seriously tempted to braze a bung in the radiator for a sensor there.
As I mentioned originally I am going to wire up with a manual switch for now and get a feel for how often the fan needs to come on before I do anything with a sensor. After that my plan is to use a thre position switch on-off-on. First position to auto operation, then off, then manual high speed.