[Tommy]

Generally speaking, temp sensors complete the circuit that powers the fan by closing a switch to ground when the temp gets high enough. Either sensor might serve that purpose. One way to figure out which controls the fan is to trace the wire from each sensor and see where it goes. Another way is to disconnect the wire at the sensor while the fan is running. If the fan stops, that is the sensor controlling it. . . . BTW, a loose or frayed wire to the sensor that is inadvertently grounded could also cause the fan to run continuously.