I am trying to change out my old thermostat which uses a mercury switch to a Honeywell ct2800 programmable thermostat. The old thermostat which is also a Honeywell has just 2 wires connected to it and none of the terminal posts got any letter markings. There is no instructions on the ct2800 on changing out a thermostat with 2 wires. Can anyone tell me which terminals to connect the 2 wires to? I connected the 2 wires to terminal W & G but it didn't work so I disconnected it and used my ohmmeter across remaining terminals to see which terminals gives me a short as I turn temperature 10 degrees above room temperature. None of the terminals went from open to short as the temperature was increase 10 degrees above room temperature. Forgot to mention this thermostat is for a gas furnace