I had an AC person come to my house to fix my AC. Here is the background: I installed a new thermostat this winter and the heat worked fine. When I went to turn on the AC it would not work. I told the AC guy that I was the one that had installed the thermostat. When he first arrived he looked at the thermostat but he did not open it up and look at the inside. He went back and forth from the thermostat to the furnace to the outside AC unit. He then told me that I needed a new relay switch which would total about $216.00 for parts and labor. I was expecting worse, but somewhat relieved since the cost was relatively low. So after he installs the relay switch he comes back into the house and then looks inside the thermostat and tells me that I have wired it incorrectly and he shows me the correctly wiring. He then correctly connects the wires. I didn't think about it until later, but shouldn't he have checked the wiring first? How did he know the relay switch was bad if the ac wasn't turning on in the first place? Any ideas or thoughts would be appreciated. Thanks.