We decided to restore and test our radiator fan switch rather than replace it figuring that if it worked well there was no reason to change it out. First step was to restore it. This was easily done with some elbow grease for the hard grime and a low pressure blast with glass bead to give it its final finish.
Below the grime we revealed the operating temperature for the switch and tested it using heated water, a thermometer, and a continuity tester. The switch works in a very simple way; it is screwed into the radiator and comes in contact with the engine coolant. When the coolant reaches a pre-determined temperature, the switch is activated and completes the circuit to the radiator cooling fans thereby turning them on. When the coolant cools enough the reverse takes place and the fan motors are turned off.
Another part done and ready to join the soon to be painted radiator.