I had a problem A/C, that had had a rash of other "technicians" from other companies work on it. These other people were pretty much clueless. One company, when the two stage thermostat went out, put in a single-stage thermostat, and rewired the main unit to run in high speed, only. When they came back to put in the two stage thermostat, did they put the compressor wiring back? Nope. Only today, 4 years later, did the KNOWLEDGEABLE fellow (Mark) at Vaught fix all of the screwups done by others. Worse, many companies came out (Amercian Conservation and Air, Strand Brothers) and totally missed the screwed up system. Worse, they tell me the system needs to be immediately replaced.