Thermostat not controlling the HVAC

[Mjmbkk]

The thermostat is not controlling the HVAC. It is running so the time. Changed the setting to cool, heat & eco. It only runs the air con . It won’t change to heat or eco. 
I’ve reset & then set to facility settings. Checked the wiring. It’s been working fine for years. 
i have to turn off it if with the circuit breaker. 
All indicators, show everything is working fine. 

[Guarcax]

Hi there!

Thanks for posting in the community. 
I’m sorry for the inconveniences that you’ve been experiencing with your Nest thermostat. I understand that you’ve been using your Nest thermostat since years ago, but recently it stopped controlling heating and echo, it does activate the air conditioner but cannot change to heat or echo. No worries, I’m glad to help you in this.

To further assist you, I will need some information. Here are some questions for you:

• What is the model of the Nest thermostat that you own?
• Does the thermostat screen indicate that it’s actively calling for heating?
• What type of furnace do you have? (gas, electric, etc.)
• Were you able to put labels on the wires?
• Do the LED lights blink on the HVAC control board?
• Have you recently experienced a brownout or blackout?

In the meantime, you can check the following articles for further information: How to tell which Nest thermostat you have and Troubleshoot strange heating or cooling behavior.

I will be waiting for your response.

Regards,

Daniel.