C-Wire Adapter Install Help / No Control Board & No C Wire (Thermostat)

[Crissy]

@speadie You seem to be the guru here… I’ve spent 4 hours between looking at my unit’s wiring and the forums. Can you please help?

Old thermostat used a jumper between Rc and Rh. Appears that the heat in my unit is an “accessory.” I live in Florida so I use the heat maybe 2-3 nights a year.

Unit does not have control board and no C wire. A traditional thermostat wire was spliced in before with a spare/unused blue wire.

Everything in my house was previously rigged by amateurs, countless hours wasted trying to figure out what they did. With everything.

Please help a single woman who has to DIY everything on her own!

[speadie]

I think you’ve got a blue wire hiding in your wall.

If that’s the case, and the blue wire is connected all the way through, you can skip the C adapter and connect the blue wire to the wire nut marked C in this image.

Your diagram looks something like this.

If that doesn’t work, then your blue wire is not continuous and you would need to use the C adapter.