I'm trying to utilize a spare wire as my C wire for my new thermostat. A lot of what I've read online assumes you have these simple, lettered terminals in your furnace. However, that's not the case in my system.
Here's the previous wiring:
I noticed a spare couple of wires in the conduit, so I looked inside the furnace and found the yellow one I'd like to make my C wire:
Here's the inside of the system. No nice, user-friendly terminal screws, just a bunch of wire nuts!
Here's the schematic.
It's so old it obviously doesn't reference a c wire, but I'm wondering if it's possible for this system. I tried joining into wire nut with the G (green) wire, because apparently that's an alternative power source for C. However, when I tried that, the thermostat would power on at first, but it seemed when the fan tried to turn on, the system would trip and the thermostat would lose power altogether.