does anyone know what exactly this switch does (#16 in the picture below)?

 

San Leandro just calls it a thermo switch. Isn't that in the radiator return hose? I think it turns on the fan.

nicer pictures

 

yeah its just a temp switch that is open or closed at or above a ceritan temp that is the one that controls when the radiator fan turn on or off.,

and the one going into the back of the block thru the water pipe is the ecu water temp sensor.

 

ok, thank you guys for your information