Hello,

We just moved into a foreclosure house that the thermostat was missing. I believe it controls both cooling and heating. There are four wires: white, blue, black and orange. Can someone help me to identify them please? I've called three technicians and no one wants a small job as to install a thermostat. Thank you so much!

Check these sites out.

Thermostat wiring colors and furnace terminal designations repair.

Thermostat signals and wiring - Transwiki

Most thermostats are labeled inside. I've wired a few thermostats, but not enough to know the colors by heart. It seems to me that your colors aren't the ones I'm used to seeing. Some people don't follow the color codes like they should.

Thos are not the usual colors. I recommend you get into furnace/air handler and see where the wires are connected. It should have the same wire terminals inside there so you can see what is what. Also check the wire colors on the outside unit.

You should have red, white, yellow and green for a four wire system.