Hi fpate,
Thanks for reaching out to our community.
I’m sorry to hear that your Nest Learning Thermostat (3rd gen) that is set in heat-cool mode with fixed temps keeps changing the AC settings to 71 deg. I understand how frustrating it is for you to keep resetting it to 73, but it always goes back. No worries, help is here.
Before I start further troubleshooting, let me ask you a few questions:
- When did the issue start?
- What other strange symptoms have you experienced since the problem started?
- Are there any error messages? If so, what are they exactly?
- Is this a new installation?
- What kind of HVAC system do you have? (Heat pump, conventional system, etc.)
- Do you notice any intervals or specific patterns between these strange behaviors? When was the last maintenance check for your HVAC system?
- Have there been any recent changes or upgrades to your HVAC system?
- Is this the first time you're activating heating or cooling since the season changed?
- Have you checked the power readouts on the Nest thermostat?
- Do you have a common ground wire or C wire?
- Are you familiar with the C wire?
- Have you experienced any power outages within the last few days or weeks?
Thanks for your kind attention; I will be looking forward to your response.
Best regards,
Virna
