AC cooling intermittent now nothing

[thor0812]

On my 2000 Silverado, ac started cooling intermittently. Would work when I would first crank in the mornings and would cool all the way to work (approx 30 miles). In the evening when temps were hotter it would cool about halfway home then go to ambient temp. Occasionally it would start to cool again just before I got home. Today I left home and drove about 20 miles and the cooling went away and now wont cool at all! When I got home I checked and the compressor isn't engaging. I checked the low pressure switch and nothing. Checked all connections and fuses and all look good and tight. I checked for power to the compressor with a test light and there is power to the compressor. Any ideas? Is the clutch shot?? Any of you Chevy gurus ever run into something like this before? Of course this doesn't happen in September or October. Its gonna be in triple digits for the next few days here at least so if yall have any ideas please give me a shout!
Thanks in advance