Ok so ive been dealing with this for about a week already. Car is a 2003 svtf and my fans will not come on without a/c on which causes overheating while sitting. So everything cooling wise, minus the rad and fan assembly, is brand new since i built the cyl head a while ago wp, thermo, thermo housing, cts, fan resistor, resistor pigtail have all been replaced. Also have done about 5 flushes total just incase anything was in the water jackets and plus it sat for a year. Anywho with the a/c off after driving and idling the temp clibs to about 228f with no fans, which is almost to the red on water n oil temp, turn the ac on and both fans turn on and temp goes back down to rougly 197f-195f and is normal. Did the old jumper-rooskie from rl15 to f1 with key on n both fans engage with resistor plugged or unplugged. Oh and it has heat even when cold so no bubbles in system. When the car was tuned i dont believe fan temp was ever messed with but no way checkin now since my xcal was stolen by my old awesome roommate. Any suggestions on what is goin on or anyone dealt with something similar?