Newbie -2000 Silverado A/c Problem

[MerriAnn]

The Air Conditioning does not work. Compressor does not kick on and off. When temp. dial is turned torwards hot or warm, them compressor will start kicking off and on., like it should. Bypassed low pressure switch, compressor still won't kick on and off when the A/C is on. Checked connections to compressor, it has the right voltage. Freeon was checked and it's full. Once in a great while, it will work for a short period of time, like 3 to 5 minutes and then the compressor quits kicking in and out. Checked condensor and it is free of debris. I put a new compressor belt on. The heat works great. Accuator door is working properly. This truck is a 2000 Chevy Silverado 2500 4x4 with 6.0 liter, Automatic trans.