Currently I have dual transformer system From heat >> RH & W1 From cool >> Y1, Rc, G

Honeywell provides a C wire adapter and also mentioned turning an unused wire into a C-wire. I do have an unused wire from the cool side. Mentioned in the manual is all about joining the adapter OR if there is an extra wire to furnace. My furnace wire up to the thermostat is only 2 wires.

Is it possible to use the cool transformer for the extra wire? Since I do have 2 unused wires


  • Can you post photos of the wiring at the thermostat and at the air-handler please? Jun 28, 2020 at 2:53
  • @ThreePhaseEel imgur.com/gallery/YV8IkLE
    – ATS
    Jun 28, 2020 at 13:32
  • And @ThreePhaseEel imgur.com/gallery/OlZkpbH
    – ATS
    Jun 28, 2020 at 13:39
  • 1
    It actually looks like the Blue is to the C... so can I just use that in the thermostat ?
    – ATS
    Jun 28, 2020 at 15:05
  • Did you ever get this resolved? If so, please give a check-mark to the answer that helped you the most, or write up your own answer explaining what you did to get it fixed and give yourself a check mark. That will help others with this kind of problem know that this has a resolution and is a good place to look for their answer
    – FreeMan
    Jul 28, 2020 at 16:13

1 Answer 1


I'd use the blue wire from the air handler as your C wire

From the pictures given, it does appear that the blue wire from the air handler is connected to C, so I'd just use that as your C wire. Let us know how it goes!

  • Yup! Worked perfectly ! Thanks for your time!
    – ATS
    Jun 28, 2020 at 18:55
  • 1
    @ATS -- we thank folks around here by upvoting and/or accepting their answers :) Jun 28, 2020 at 19:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.