I have a 2-stage furnace (Trane TUD100R9V5K0) and a 2-stage thermostat (Trane XT302C). I recently replaced a defective control board in my Trane furnace. While doing that, I discovered that the white wire from the t-stat was connected to both the W1 and W2 terminals on the furnace control board. I connected the new control board the same way for now, but I don't think this is the correct wiring to take advantage of a 2-stage system. I checked at the t-stat and found that the White wire is connected only to the W1 terminal. Nothing is connected to the W2 terminal of the t-stat. The black wire which I believe would normally be connected to the W2 terminals at both the t-stat and furnace is present, but unconnected at both ends. Is there any reason why someone would wire it that way? It was like this when I bought the house. I want to wire this thing correctly, but before I do I wanted to find out if there is any reason to leave it as-is. Thanks.

Hello. I have a 1995 York Diamond 90 furnace that uses Natural gas. No AC in the house, just forced air heat. I am switching to a new Honeywell thermostat and need to double check about the wiring before I do this. Currently there are only two wires connected to my thermostat and furnace, white and red. The letters on the furnace read like this: Y W R G C The wires are hooked to W and R and the same on the thermostat. There are no other wires available so I know I need to run new wiring. I think that if once I run the new wiring, if I hook up W R and C on the furnace and the thermostat I should be back in business right? Do you see any need to hook up the other two wires as well, the Y and G? Not really sure what those are for. Thanks for any help!! Craig