Just installed a Hunter 550 Thermostat from a Honeywell and the AC won't shut off. Have it set to the standard auto program and the temp setting reads 78, but it's actual temp reads 71 and it's still cooling. My old thermostat had W (white), G (green), R (red), C (blue), Y (yellow). The instructions said not to hook a C (common) wire to the new unit, so I only hooked up the other 4 wires. There is also a brown and orange wire in my wall, but those were not used before. Should I have another wire hooked up? I'm so confused!:confused:

Is this a gas furnace?with electric A/C ? You may have to go to the furnace and varify the wiring ,make sure the wires are connected to the same terminels as at the thermostat, some people do not pay attention to color code.

I would very carefully read the instructions again. Then call any help number in them. Sounds like a bad stat to me.