Interesting post Richard, and something rarely thought of to a DIYer. That loosened a memory I had from an installation I did in the early eighties. I took a Fridgi King underdash unit out of a junk truck and installed it in my 68 Ford 100 I had restored. I did this at a friends auto parts store/shop. We flushed the system, installed new dryer and hooked everything up, evacuated and charged it. No cold air. My friend began to feel the hoses and lines. When he got to the flare connection at the condensor, he said "feel this". The line was HOT to the fitting. On the other side it was cool. He took a small hammer and gently tapped on the fitting. Whatever was blocking it came loose and the system worked fine for another 12 years.