any time the a/c is on you should have a fan on.. its part of the a/c circuit to have a fan running when the a/c is on. the other fan is controled by the heat of the engine.... i think it is the Engine temp. sensor... cost about $15 at auto zone... the sensor is screwed into the engine block and has two pins coming out the top that the wiring harness is connected to it with two wires.. not the one wire temp. sensor for the temp. gauge on the dash this is different and only has one wire, and cost about $6.00..
hop this helps.
