'01 Sierra A/C control

Has anyone had any troubles from their A/C control board? I have a '01 2500HD sierra that is experiencing some non-functioning A/C compressor. The A/C light comes on, but there is no cool refreshing air. I just replaced the compressor belt and had great cool air for about three weeks.

I have a set of A/C gauges, vacuum pump, and a Haynes A/C manual. What do I need to check?