what is that switch for in the bottom of my radiator pretty sure from what ive read that is sensed temperature for the bac system but this guy http://mazdarx7.iougs.com/idlecontrol.shtml says its to sense air outside the radiator???? please help cuz i wanna drop in my racing radiator and it doesnt have ports for coolant level sensor or this switch. ty

 

This is an FC, correct? Remove the switch on the bottom corner of the radiator & jumper the two harness-side connectors together. The switch closes the circuit at a low temperature (something like 60F) and is involved in the 3k RPM warm up circuit. The engine may not rev up to 3k RPM anymore on cold starts, since the ECU will always think the water temperature ( not the air) is 60F or higher.