Sunblock not working

[chukukchi]

I have two Nest Learning Thermostats (3rd Gen) in the house with a dual-zone HVAC system. Lately, both thermostats have been receiving direct sunlight in the morning, but the Sunblock function is not working.

Here is what I have already checked and done:

1. There is no direct heat source behind either thermostat.
2. I turned the Sunblock function off and on, but it did not make a difference. Both thermostats still do not seem to detect the temperature correctly.
3. I turned the thermostats off and on too. No difference.
4. No "sun" symbol on the thermostats.

Are they faulty? What can be done to fix this issue?

[luciaaa]

Hi, @chukukchi!

Thank you for contacting the community. I'm sorry to hear that your sunblock isn't working correctly and that your thermostat isn't detecting the temperature accurately. I'd be glad to help you.

I appreciate the details you've already provided and the effort you've put into troubleshooting. To better assist you, please provide the following information:

• When was the thermostat installed, and where in your home is it located?
• What is your country of residence? 
• When did the inconvenience start? 
• How significant is the difference between the temperature reading on the Nest thermostat and your thermometer or other thermostats?
• Is the problem constant, or does it occur only under specific circumstances?
• Have you made any recent changes to your HVAC system? Have you experienced any power outages?

Additionally, please share a picture of your wiring configuration of both thermostats. 

Thanks in advance for your cooperation. This information will help me to determine the best next troubleshooting steps. 

Please keep me updated.

Best regards, 

Ana

[chukukchi]

Thank you! Here is the information of my thermostats:

• When was the thermostat installed, and where in your home is it located? - They were both installed in around November 2024. My home is in Carmel, Indiana.
• What is your country of residence?  - United States.
• When did the inconvenience start?  - since Mid-February 2025. It could be earlier but I just realized of the issue recently because in the morning I could see that the current temperature shown could be as high as 76F-78F, but it could not be true because I never set the heat so high.
• How significant is the difference between the temperature reading on the Nest thermostat and your thermometer or other thermostats? - About 6F-8F differences. So the Nest thermostat showed 78F, but actually the room temperature was only 70F. Because after the sun moved and was not shining directly on the thermostat, they dropped back to 70F.
• Is the problem constant, or does it occur only under specific circumstances? - It happens every day now. Always in the morning when the sun shines directly on them.
• Have you made any recent changes to your HVAC system? Have you experienced any power outages? - No power outage. I did not make any changes to the HVAC system either.

Somehow I can't attach photos to the post. Here is the wiring configuration of the thermostats. They are both the same: https://imgur.com/a/g0Ib9Mn 

[luciaaa]

Hi, @chukukchi!

Thank you for your prompt response. I appreciate you taking the time to answer all of the questions.

To further troubleshoot, please let me know the internet signal strength on both thermostats. You can find this by going to Settings > Technical Info > Network.

In the meantime, please follow these troubleshooting steps:

• Restart the thermostat: Settings > Reset > Restart. The thermostat will take a few moments to restart and boot back up.

• If you agree, and only after turning off the breakers, please try to cover the wall with a duct seal compound: Apply the compound around where the thermostat is installed to seal any gaps and add insulation.

• Sometimes, installing a thermostat steel plate or trim kit can also help.

If the issue persists after these steps, please disconnect the thermostat from the Wi-Fi network for 24 hours to monitor the ambient temperature. You can disconnect the thermostat by going to Settings > Network > Disconnect.

Please let me know how it goes.

Best regards,

Ana