A/c was intermittent on mine. Had the system charged/checked and worked well for a day, then on and off, then nothing next time in the car. Called the shop and told them I was bringing it back so they could see if their dye showed a leak, then when I started the car later in the day to go there, the AC blew very cold...
In the midst of all this, I replaced the thermostat. I was not getting a CEL, or any notable problems, but I wanted to replace it before problems in winter, as this usually fails allowing the engine to run to cool.
Told the guys at the shop this after they found no leak and measured by AC out put at 41F...
Possible explanation: Thermostat was allowing engine to run cool, so the radiator fan would not trigger, which reduced AC operation, since it is the only fan.
I did look at the fan connector and resistor (they look new) and at the fuse/relay box and saw no problem there.
If it goes out again, I'll re-check the 40A fuse and fan relay, but I think it was somehow thermostat related. I don't have a scanner, but after a few key cycles, the new thermostat probably cleared the errors and the AC started working.