Air Conditioner, Erratic Operation

My 98 Maxima GLE A/C works fine on the road,but sit for two a traffic signal and the vents start pushing hot air.I checked the car in my driveway,the compressor pumps approx.two min,the suction line is cold during this brief period.but neither fan runs.I had two shops check the system,both are at a loss,as neither shop experienced this problem.System pressure is ok.They feel the problem is electrical,but differ on a solution.One suspects the auto climate control thermostat,the other the pressure cut off, or a relay.I question both,as the car works fine on the highway.Any suggestions would be apperciated.