Fan has two settings that can be triggered three ways.
Low setting about 10 degrees warmer than the thermostat. (Thermostat opens so coolant is moving through the radiator, then the fan kicks on.)
High setting that kicks on about 20 degrees warmer than the thermostat. (So if low fan isn't moving enough air to cool it down, more air will make it happen.)
High setting also gets triggered when A/C is set to MAX.
1998 Roush: M112'd Aluminum block 4.6L 2V 6 speed track car
1999 SVT: Mostly stockish
1970 Mach 1: Resto-modded monster
2000 Roush #5004 - World's FIRST M112'd V6 Mustang. Sold, but not forgotten.