I'm having this problem right now, too.
 

My AC was blowing slightly chilled, but not cold air. I don't have time to troubleshoot it right now, so I took it to a shop and they found a leak at the evaporator core. So, they replaced the evaporator core, dryer, and orifice, and I picked up the truck. I immediately noticed that while driving, the compressor cycled on and off repeatedly as you describe. The AC condenser fan runs as it should, so I suspected the system was either low or high on freon charge. I took it back to the shop, and they called to say that the issue is with the AC evap. core temperature sensor that samples the temperature of the core to prevent the compressor from freezing things up. Supposedly the sensor is giving faulty readings, causing the compressor to cycle repeatedly.

I'm supposed to be able to pick up the truck again tomorrow. I'll try to follow up here with an update to let you know if this solves the issue.

That makes senses. I suspected that might be the issue with mine, its about the only piece I haven't replaced and of course it turns the compressor on/off. That evap temp sensor is accessable from under the dash if I recall correctly.

And to a previous poster; ambient temp was about 90; low side was 45 and cycled up to 75; high side was about 200 and cycled to 275. The duct temp is a steady 60 degrees (not even close to cooling in 90-100 heat) at all refrigerant levels. I know I'm now overcharged but nowhere between empty, undercharged or overcharged did the duct temp ever get below 60.

I'll see what the tempo sensor does for me. Thanks for the input guys.

Cool! My truck received the new temperature sensor today and the shop called to tell me it's pumping out nice cold 46° degree air at all engine speeds, so it seems to have solved the problem. I haven't picked it up yet, so I haven't been able to test it and give it my own seal of approval, but so far it sounds promising.

I hope you're able to get your problem sorted out, too.