2008 Ford Focus AC Problems?

I have an 08 Ford Focus. I have tested the Freon level on it and at 75 degrees outside it is at about 38PSI while running and that is supposed to be normal. However, the ac condenser on the car still clicks on and runs and then shuts off. In the car the air gets really cold then really warm. Any ideas what this could be? The dealer just had to replace the thermostat and to do that they had to remove the ac condenser to get to the thermostat to replace it and now it does the intermittent running. I am baffled, especially since the Freon level is normal according to the gauge.