I need some help with a electrical problem with my auxiliary fan. I have replaced the switch at the dryer, checked the relays, checked the continuity between the fan and relay and switch, checked the fuses.The fan will run if you hook it up directly to the battery,but it won't come on by itself with the ac on.Any help on what to check would be greatly appreciated.

By pass the switch at the dryer, cut you key on, the fan should come on, if it does not, it may be the ground connection. Not sure of location, but the ground for thr A/C clutch is on the right side. under the knob for turm signal.