I had a neighbor install a new furnace in my house 2 years ago. He's been in the A/C business since at least the 1970s. The new furnace is one of the high efficiency furnaces that doesn't use the chimney (a Concord 90+ efficiency). Both the AC and furnace work properly, except for one problem. Ever since he installed the furnace, whenever I turn the switch on the thermostat to "Fan ON" (instead of AUTO), the Air Conditioner will also turn on and it will STAY ON, regardless of the temperature setting on the thermostat. In other words, I could leave the house for 2 hours after turning the fan switch to FAN ON, and the AC will run the entire time and the temp in the house will keep dropping regardless of any of the settings (and regardless of if the other switch is turned to heat or cool). My neighbor told me tonight that the green and yellow wires are switched and that he will be over Saturday to fix it. I just wanted to post this message here to see if he is correct...I don't want anything else to break if he is wrong. Any advice will be helpful. thanks. Todd, Omaha