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A/C Turning on When in Heat Mode Only

bdonova1
Community Member

‎04-15-2025 11:58 AM

My Nest 3rd gen thermostat has been running for a couple of years.  The other day, I noticed the A/C was running, but the thermostat is in Heat Only mode.  It happened again today.  Both times, a gas fireplace was on and the inside temp was in the 70s.  It seems like it is calling for A/C though in Heat only mode.  Never saw this in previous 2 years.

Gas forced air furnace, no heat pump.  A/C unit outside.

Wiring- Red Y1, -Green G, - Red Rc, - White W1

SW 6.3-5

Battery 3.82 volts

-Brian

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GabrielaG
Community Specialist
Community Specialist

‎04-18-2025 04:39 PM

Hi @bdonova1,

 

Thank you for reaching out to the community. I'm sorry to hear your Nest Learning Thermostat 3rd gen is not working as expected when it is in Heat Mode only, but there's no need to worry; I'm happy to help you right now.

  • Are there any error messages? If so, what are they exactly?
  • Do you notice any intervals or specific patterns between these strange behaviors?
  • Have you done troubleshooting steps? If so, can you list them?
  • Can you please send me a picture of the Nest Thermostat wiring?

Any additional details you can provide will be helpful.

 

Best regards,

Gabriela

 

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