We just got a new WiFi capable thermostat that, unfortunately, seems to use a form of power stealing in order to charge itself. The problem here is that our house is actually quite well insulated; the unit doesn't run for very long, so the thermostat keeps turning off the WiFi as the battery falls too low.
When I first installed the new thermostat, I found the blue wire that was listed as likely being the common wire; however, when I connected it, the thermostat indicated that there wasn't any power and prompted me to remove the wire. So I went up to the furnace, hit the breaker, and popped open the panel. I can see the blue wire appears to just be wrapped around the outside of another wire rather being connected to the furnace.
So... we have this confirmed: Yellow wire for cooling, white wire for heat, green wire for the fan, and the red wire for power. I can only confirm because the thermostat, for all the WiFi woes it seems to have, is working to control the temperature just fine right now.
Here is a picture of the wiring at the furnace; is this enough for anyone to tell me where I should be connecting that blue wire, or should I go ahead and call an HVAC technician out?