I never understood it, but if I ran the car on the Interstate for over 15 mins. it would start to blow hot. When I got off the Interstate and slowed down, the AC returned. It hasn't happened again since I got it recharged. If my mechanic fixed something else, he didn't charge me for it.

 

My A/C never gets hot, but like dstt said, if I give it gas to accelerate or pass the fan seems to slow down, and the volume of air coming out decreases drastically. If I'm just cruising down the highway at a steady speed, it works great, it's around town with the stop and go that it cuts in and out.

 

Could be to high preassure in the A/C system. There is a sensor near the dryer which cuts off the A/C compressor when the preassure is to low or too high. I don't remember the values - have to check (they are stamped on the sensor). If You push to the floor, RPM increases causing higher preassure inthe system when A/C clutch engaged. To much R12 added during A/C fill ?