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New installation

Community Member

Good day.

We have a mixed (furnace/heat pump) system and our third gen nest thermostat was installed by a tech person not an HVAC expert.

It seems all heat is currently being generated by furnace (outside temp 38-45F). Sometimes the house feels pretty cold but additional thermometer on a fan confirms nest's stated temperature. As far as I was able to tell wiring was done correctly and S wires were capped since nest does not need them. Does this sound like it is working well? It seems it was set on heating stage 2, is that part of the problem? Heating systems and this type of tech is not my area of expertise. From reading online it seems that it is not and I am wondering if I should have an HVAC person come in and make sure it was set correctly.

If there are other resources here please let me know, this is my first post.  



Community Specialist
Community Specialist

Hi hulumaxflix, 


Yikes! Let's see what's going on. A few questions: 


  • Are you located from North America or Europe?
  • What type of Nest Thermostat do you have?
  • Does the thermostat screen indicate that it’s actively calling for heating?
  • Did heating ever work with the Nest thermostat? If not, did the heating work with the previous thermostat?
  • Did you turn off the power to the HVAC system?
    • Did you recently turn off any breakers?
    • Have you recently experienced a brownout or blackout?
    • Is there a light switch near the heater that controls an outlet?
  • Did you select the correct fuel type?
  • Do the LED lights blink on the HVAC control board? If yes, locate the light.
  • When was the last time you changed the furnace's air filter?
  • Have you experienced extremely cold weather lately?
  • Is this the first notable temperature drop of the year in the area?


Also, kindly link here the photo of your previous thermostat wiring configuration and how the thermostat wires are connected to your Nest Thermostat base now. 


I'll look forward to your response. 




Community Member

Thank you kindly Zoe. I very much appreciate your response.


Before answering your questions I would like to clarify that I have now confirmed that the heating is working, it is just reflexing to furnace rather than heat pump first (in adequate temperature). We believe in the past the system employed heat pump first. 


1. North America. 

2. Nest learning third generation

3. Yes. Heating stage 2.

4. Yes/Yes. Please see clarification above. 

5a. Yes, at the time of switching the thermostats. Since they were flipped back on. In the past this had occurred without issue. 

5b. Power went out in our neighborhood a few days after installation due to bad weather. Everything else has been working well. 

5c. Not that we can see.

6. We tried both electric and "I do not know". The latter followed by HVAC when prompted for type (e.g., flooring, etc.).

7. We cannot see this in a panel.

8. Yes, 3 months ago.

9. Variable between lower than 45 and higher. 

10. See 9 above. Variable. Lowest has been about 37. 


Thank you again very much, pictures attached below, 


Community Member


Hey everyone,

I'm chiming in to see how I can help.

Thanks for looking into this, Zoe.

@hulumaxflix, we appreciate you providing more details. Big help! Incorrect wiring configuration could cause odd HVAC system behaviors. In addition to what was asked above, the wiring diagram on your thermostat display appears to be different. Can you pull your thermostat display and take a photo of its actual wiring set up?

Keep me posted.


Community Member

Thank you Mark and Zoe. Please see the requested image attached


Hi hulumaxflix,


Thanks for keeping us in the loop. Please move the blue wire to the O/B terminal and connect the black/brown wire to the C terminal for your 24V common. Once done, make sure to confirm the wiring changes prompt that will appear on the screen. If none, press and hold the button or the screen for 10 seconds until it shuts down to refresh. Then, activate your HVAC system.

Note: Turn off the power from your HVAC system at the breaker box before touching the wires.

Let us know if that works.