He carries a tiny tool bag, and a CPS temp seeker TM250. ( a four station multi-port Digital thermometer), No manifold gage. He showed me how to check charge with temperature only.
Basically, he hooked up a temperature probe to discharge port at the compressor, a probe at bottom of condenser, temp probe at Suction (maybe 1-2 feet from the compressor).). He could tell if it system is over charged, or under charge. His word to me was: temperature, temperature, temperature. He would say something like ; this one is probabbly two pund short, this one is probably 3 pound short. by garr ...lly, he was right on the money.
I ask him why he doesn't take care it himself; His reply was; if the shopping center knew he can do all these stuff, they simply add xtra work without more compensation. So they always hire an outside contractor.