Showing results for 
Search instead for 
Did you mean: 

Heat Pump System / Air Handler - Honeywell to Nest Thermostat

Community Member

Previous Thermostat:  Honeywell Home TH6210U2001

Air Handler (attic): Coleman AP36BX21C

Heat Pump (outdoors) : Coleman HMH72B361S

Current Nest NT2020 provided by JCP&L 🙂 

Prior to making the switch, the Honeywell unit worked well. (6pm yesterday).

Wiring is pretty straight forward and color coded; Red (R), Yellow (Y), Blue (C/Common), Orange (OB), White (W), Green (G). After installing the new thermostat, I received a note that *OB was undetected. It appears Y and OB are not detected until unit kicks on, and then Y gets detected, but OB remains undetected (locally, on the nest unit).

Nevertheless, the unit was 'working', but only blowing out cold air.

I reached out to support, we've swapped numerous wires for some test (Y to W, O/B to W, etc), unplugging G - some of these I was quite skeptical of as unplugging blower (G), wouldn't change temperature, but I am sure they had a reason for all of these swaps. After an hour and a half on the call, they told me to switch back to my old thermostat and ensure it worked. It did. At this point I gave up and they suggested I call a partner to come out and install for $130. 

Does anyone with some HVAC experience or experience installing these units with a full electric heat pump (w/ emergency heat) ? 

I have reinstalled the thermostat with dual heat; emergency heat activating below 30 degrees.  However, the house went from 75 degrees (previous thermostat test) to 67 degrees, with heat activating at 70 degrees... Its actually blew out colder air and dropped from 69 to 67 in about 10 minutes. 


I have attached both previous wire diagrams and current (on nest). Brown wire is not connected and was not connected; which confused me a bit as Brown is typically emergency system (albeit, we do not have an emergency fuel source, its just an electric 'strip' when E-H is activatedPXL_20221211_015438086.MP-min.jpgPXL_20221211_142514886.MP-min.jpgPXL_20221211_143503341.MP-min.jpg ... Any suggestions? 


Community Specialist
Community Specialist

Hello KnockoutLounge,


I'm sorry for the trouble this may have caused you because your system blows cold air when in heating mode. Let's see what's going on.

Could you provide us with the case number from the support person that you spoke with? Also, have you tried the steps in this guide?


I'll look forward to your response.




Hi there,


I'm checking back in — how's it going? Still need our help? Let us know so we can assist you right away.



No longer need help. Google Support led me down the wrong path, but Reddit was able to assist.  I am all set.


Thank you.

Hi KnockoutLounge,


Woohoo! Thanks for the update on what you've done to have your concern rectified — give yourself a pat on the back for a job well done!.


It looks like we have come to a solution, so I'm going to lock this thread in 24 hours. If you have any other concerns or questions, please feel free to create a new post.