Thermostat wiring help please!

Hello everyone, I’m having issues with my thermostat not turning on my ac compressor. Heat works fine but when I go to turn on ac and cool down, seems fan only runs and ac doesn’t. These are the wirings of the furnace.

Anything will be helpful. Thank you!

Wiring at thermostat

Is that blue wire at the furnace also available in the wall behind your thermostat?

If it is, the fastest and easiest way to fix the problem is to connect the blue wire to C on both sides and remove the C adapter. (Then reset your thermostat and remove and re-add it in the app.)

If it is not available, you need to find the point that the Y wire is spliced to send the signal to your compressor and remove the splice so that the furnace has an uninterrupted run of wire to the thermostat. Then you need to wire in the compressor directly to Y and C on the furnace board.

The wire nut that is near the terminals is covering where the red and white wires are connected to the air handler terminals. I assume those are the wires that are coming from your outside unit. I can’t tell 100% certain because the wire nut is in front of it, but it looks like you have connected both the white and the red wire to the same terminal (C).

If that is the case, then that means there is no chance the outside contactor will ever work. One of the wires will need to be connected to the Y terminal on the board, but the other wire needs to stay connected to the C terminal.

I saw that, but i think the red wire is wire-nutted to the other red wire that runs across the board, leading me to think that that wire is connected in parallel with the transformer terminals R and C
Most likely, the A/C contactor is connected in series with the Y wire, between the thermostat Y terminal and the furnace Y terminal.

Hard to see many posted photos.
Either just a bundle of wires.
Or obscured markings.

Need both closeups and wide angle views.

Yeah I’ve been looking, and maybe the red one goes to the wire nut… I think we need another picture where the wire nut is not covering the terminals and of what’s tied together in that nut :slight_smile: