2004 Chevy 2500 Silverado 6.0 V8 Gas.?

[bgilbert605]

OK... Just changed the Orifice tube changed evacuated and recharged. no leaks were detected. when its sitting at idle running, AC goes down to 37 degrees. that's great. once i start driving it down the road the AC Compressor kicks off. and blows hot air. when i come to a stop.... the AC kicks back on and blows cold again... does not make any sense... anyone know what it could be????
Does not have the Auto temp control and the pressure is perfect.....