1999 Chevy S-10 4.3L 90,000 miles. AC Problem

The low side is showing a full charge and the compressor will cut on and run the press. Gauge up into the red (which takes about 5 secs) and then it shuts off. It's just a constant 5 secs on 5 secs off process. There was some oil build-up by the low side switch which I replaced. Alot of people have been telling me this is a blockage somewhere in the system and it needs to be cleared. Is this probable and if so, how can I clear it myself?

Thanks alot,
Karl