This trick electric fan switch is a normally open temperature switch with 1/2" NPT male threads that screws into your intake manifolds water passage. When the coolant reaches 185°-215°, the contacts on the cooling fan switch close, activating a relay which directs current to your electric fan. When the engine cools, the contacts on the fan relay switch open, and the fan stops automatically. This radiator fan switch arrangement is not adjustable, but is more rugged than other temperature fan switch setups.
NOTE: This thermal fan switch must be used with a fan relay. If installed as a gounding fan switch, it will burn out. We suggest using this temperature fan switch with our relay 910-64044. Make sure the fan switch is mounted in the manifold or radiator tank so that the bulb is submerged in the HOT engine coolant.
910-64013 Instructions (PDF)