I am trying to see if I can fix my girlfriends AC unit (if it is an easy fix). The air comes on when you turn on the thermostat, air starts blowing, but it is not cool. Checked the outside unit (compressor) and it was NOT running. No fan, neither pipe was cold or hot, nothing from the outside unit. Last time this happened, I went to take off the side cover and it started working again, just like that. So this time I thought I could do the same thing, like there was a safety switch on it that was not getting triggered. No such luck, took off the cover, there was no switch and I didn't see any loose wires. Checked the voltage, there seems to be voltage 24vAC coming in from the thermostat wires, and there is AC power (110vAC I assume) coming in from the breaker box. Beyond that, don't know what to check. Thoughts? Help?