I have a 2 door 4wd 1992 ford explorer and the ac compressor wont turn on.?

it has plenty of freon in it, checked the pressure and it is high enough for it to run. one day it just quit engaging. you can send power to it and it runs. when we take the plug off voltage is there. when we put it back on the relay keeps clicking and the voltage disappears. we already changed the relay what is left? my step dad says the tps is supposed to kick off the ac when the engine is at full throttle and that the tps could be bad. i had a hesitation problem in the winter time that would come and go as the engine was cold or warm. its getting hot out and im tired of this stupid problem if it could be an easy fix. any suggestions anyone?!