Ok, I have a 91 silverado 2500 ex cab, 5.7 L automatic. Several years back, I had a local AC shop convert my system over to 134A, new accumulater, Compressor, etc. Today, I tried to recharge the AC unit with a DIY "AC PRO" from the local autoparts store. I'm pretty sure that I followed all the instructions, including watching a couple of you tube videos. I filled the system to the high side of the "Green" area, but no cold air. The compressor clutch keeps kicking in and out about every two seconds and while this is going on, the pressure reading jumps (with every cycle) from a little below the green zone, all the way to the high side of the green zone.
Anyone have and advice?

 

You really need to get a real set of AC gauges so you can read both the high and low side pressures at the same time. It sounds like your system is low on R134a, but without knowing what the pressures are, it's tough to diagnose. FYI, O'Reilly Auto Parts has loaner AC gauges in their loaner tool program, and I think AutoZone does too.