No C Wire? Honeywell Home Smart Thermostat

[@ShadduckGuestRoom]

Thanks for taking the time to post this, but here's a TIP for others: Check thoroughly, both ends of your existing thermostat wire bundle, you may find a hidden C-wire! It may be folded back/tucked into the wall cavity, or may be snipped off at the end of the cable's insulating sheath (not needed or used with the old installation)... While preparing to upgrade to this exact same Honeywell model, I found mine was hidden there all along! Thinking I had no C-wire (it wasn't visible at the old thermostat end), I've been delaying my smart thermostat install while watching several of these how-to videos. Finally feeling ready to do the deed, I opened the furnace panel where the thermostat wires enter, and found an unused blue C-wire wrapped around the thermostat bundle/cable (on the thermostat end it was cut off at the insulating cover, not easily visible). The "C" terminal was there and connected to the remote condensing unit, but previous installer didn't attach the thermostat wire bundle to it, as it wasn't needed with that old battery operated thermostat. Took about 10 minutes to power off the furnace, attach the blue wire on the furnace end, then run up to the thermostat and expose/strip the end of the blue wire on the thermostat end. Thankfully, there were several inches tucked into the wall.

[@Joyce-r4f]

I have a electric dual,heat and air,the fans come on for heat,no heat comes out HELP????

[@icandothat905]

What are the wire colors of your original thermostat?

[@icandothat905]

Thermostat wire colors typically correspond to specific functions in an HVAC system. Here’s a breakdown of common thermostat wire colors and their functions: 1. Red (R): Power from the transformer (usually 24V AC). 2. White (W): Controls the heating system. 3. Yellow (Y): Controls the air conditioning system. 4. Green (G): Controls the fan. 5. Blue or Black (C): Common wire (used for completing the circuit and powering smart thermostats). Additional wires may exist in more complex systems, but these are the most standard.

[@icandothat905]

I replaced my common wire (blue) with the existing green (fan) because on my zone there is no fan control but the wire was there. It sounds like you have no complete circuit on the white (heat) but you do on the fan.

[@Joyce-r4f]

Thank you so much.been trying to get my heat back. I'm praying this works.

[@Joyce-r4f]

HELP

[@icandothat905]

How did you make out?

[@haroldcampos9661]

You lost me at the splices… 😥

[@icandothat905]

My system has the ac controlled in a different zone. My setup on my main floor, where this is, uses the same wire configuration: white for heat, red for power, and there’s an extra green wire for the fan. This connects to nothing. I took the green wire and used this as the common wire (typically blue) which provides constant 24v to power the touchpad. I used a voltmeter to find the hot and put the green wire on this, and then put it into the common/blue spot on the touchpad.

[@icandothat905]

Your thermostat will be connected to your 120v system with a unit that converts the voltage to 24. The splice went from the hot to the green wire as described in my other comment here.