When going down the highway the air conditioning blows fairly cold when the temperature outside is below 90 degrees. I notice when it is hotter than that, the compressor will kick off for 1 or 2 minutes then will come back on for several minutes then kick off again over and over. While sitting in the driveway the compressor stays on. It does not cycle on and off like it is low on freon. Not sure if this is a separate issue but this car has never blown cold air in stop and go traffic. It will only blow cold air on the highway. Everything accept the compressor has been replaced on the car within the last 8 years (condensor, evaporator, orrifice tube, drier, pressostats). I have heard mention about a thermostat running to the evaporator and a thermal cutoff on the compressor. Could these have anything to do with the problem? I am also wondering about a high pressure cutoff??