Sounds like it may be over pressurized. I over pressurized my system once, and it would blow cold, then make a "click/clunk" sound, and blow warm, and repeat. I couldn't tell you how I solved it. The mechanic said that he thinks the pressure was released when he fit his gauge on the high side, and after that, the PSI numbers were perfect, and the air is ice. IMO, I'd take it back to the certified technician, and have him check everything over again. It may be a bad compressor or compressor clutch though.