Behind my old thermostat I have only 4 wires. Red, Green, White, and a Blue wire connected to Y. I figured I just need to go to the furnace and connect the C-wire extender to the board.
When I got down there I found this and am confused on what to do next. The spliced wire and the blue wire are connected to the Y terminal (you can’t see it in the pic) The board is set at G, COM, W, Y, and R in case this isn’t clear.
Looks like I do have a C-wire but it’s not run up through the wall. Does anyone know what my next step should be?