My First thread anywhere in a very long time....
In the past weeks I installed new aluminum radiator. I'm not going to use the probe type switch the you push through the radiator. (The reason) Over time they work lose a start rubbing and damaging the coolant tubes. Besides, My main fact is it's a new radiator and the probe is mile too short. This switch will go into the intake manifold at the coolant return. I'm setting it up using a N/O (normally open) switches. (one prong) The one I'm using is a 175 degree so at 175 the fan will come, also using a over ride toggle switch that will allow full time fan, if needed. Both the switch and toggle are grounds to the relay (ONLY).
Some knucklehead had the wiring to the fan all screwed up from the first install on the old radiator.
I'm going to set up the new rotary fuel pump the same, the main reason for this switch is to kill the fuel in case the engine dies, or a accident, no oil pressure, no fuel. This is recommended, to keep you and your friends safe from a gasoline fire.
Attached is the wirng diagram