are the lights flashing on the climate control unit? do you have Automatic AC?
how aboutthe clutch on the compressor could it be not holding? it has a electo magnet that engages the clutch i believe.

have you tried to by pass the low pressure switch when the compressor turns off? take a piece of speaker wire and jump the connections in the plug to the switch. the switch is loated on the same line that has the service port for the freon, look towards the back of the line near the firewall there you will see the wire harness plug into the sensor. could be a bad sensor turning off the compressor.

try cleaning the temp sensors above the front doors behind the grad handles, use alcohol and a Qtip.

Dan