Nest Thermostat (Gen 3) is in heat but HVAC system not coming on

[JonR75]

I have two Nest, 3rd generation thermostats for a split level house but they both control the same HVAC unit with a heat pump. Now the system works in cooling mode but when I turned my thermostats to heat, the system just blows cool air and the compressor never comes on to heat the house. I checked all wiring for both thermostats and they are good. Ran the compatibility checker on the Nest site and it I probably have dual fuel even though it’s all electric but I switched to dual fuel anyway. Don’t know what else to check at this point. 

[Guarcax]

Hi @JonR75!

Thanks for posting in the community.
I’m sorry for the inconveniences that you’ve been experiencing with your Nest Learning Thermostat 3rd Gen. I can see that you just installed the Nest thermostat a couple of months ago, and it was working fine when cooling, but now that you are trying to use it for heating, it is not responding. I’m glad to help you in this.

In order to further assist you, I need some extra information. Here are some questions for you:

• What other troubleshooting steps have you done so far?
• During the setup process, did you select the correct fuel type?
• Who installed the Nest thermostat?
• How many wires are connected to the thermostats?
• Do you receive any message from the Nest thermostat?
• When was the last time you changed the air filter?
• Do you have any pictures of the current and the previous wiring configuration?

In the meantime, you can check the next article: Using multiple Nest thermostats in the same home. 

I’ll be waiting for your response.

Regards,

Daniel.