My pt cooling fan will not work unless the ac is turned on. any ideas guys?

A possible culprit maybe the relay that controls both the fan for cooling the engine adn A/C. The A/C circuit and cooling circuit both share the same relay. To find the relay, look in the fuse panel behind the battery and look inside the cover. It will tell you the relay and if in doubt have someone turn on the A/C and feel the relay for clicking on and off(cycling). Also have you ever changed the coolant sensor located on the upper radiator housing? It could be a possible reason for not turing on. Suggestion, if it has never been replaced do so with a new thermostat(180 degree many pt'ers use now). Hope this ehlps you out and try you tube as well.