The SPAL cooling fan switch features 3/8" NPT threads on a stainless steel, hermetically-sealed body. Thermal fan switch threads into your intake manifold or cylinder head and activates a relay (not included, sold seperately) when the bulb is immersed in coolant that is 185° F or 195° F, depending on which electric fan switch you use. As the engine cools, the contacts on the fan relay switch open, and the fan stops automatically. Make sure the electric fan switch bulb is submerged in the HOT engine coolant. Non-adjustable radiator fan sensor. Operating Switch Range: 35° F to 480° F. Max Current & Voltage: 3 amp, 32 VDC. Grounded case only.