There is an extra wire (orange) which you can see both inside the thermostat and also in the image of the furnace. I should be able to use that for the C wire.
You'll notice that the wiring of the furnace is done with wire nuts. All of the instructions to add the C Wire that I can find are assuming that I have a C port on the furnace, which I don't, since this is all done with nuts.
My question is this: on the furnace side, into which wire nut should the orange be joined to get the correct power supplied?
Thanks so much!