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E102 Error power outage

Justinm59
Community Member

‎10-18-2024 09:21 AM

I've had no issues for the few year of ownership on the nest thermostats. Started to get e102 error on the downstairs unit when we started trying to use the heat this fall. I've checked the wiring and the furnace isn't giving any error indicator. I put on basic thermostat and the heat works again. I'd like to keep using the nest if I can get it to work. We did lose power for 4 days after hurricane Helene. Model Display-3.4 and Backplate-5.4

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Justinm59
Community Member

‎10-18-2024 09:17 AM

I've had no issues for the few year of ownership on the nest thermostats. Started to get e102 error on the downstairs unit when we started trying to use the heat this fall. I've checked the wiring and the furnace isn't giving any error indicator. I put on basic thermostat and the heat works again. I'd like to keep using the nest if I can get it to work. We did lose power for 4 days after hurricane Helene. Model Display-3.4 and Backplate-5.4

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moralesvicente
Community Specialist
Community Specialist

‎10-28-2024 05:16 PM - edited ‎11-04-2024 10:38 AM

Hello Justinm59, 

 

Thank you for taking an interest in our community. I’m sorry to know that your Nest Learning Thermostat 3rd Gen is getting the error code E102. Don’t worry; let me assist you with some troubleshooting steps and information. 

 

This error code is indicating that there's over-current or over-voltage (there's too much power that flows through the thermostat). So please follow the following steps.

 

Check the system power: 

 

  • Ensure that the power to your system is on. The power switch will usually be in your breaker box or fuse box, but in some homes it will look like a light switch near the heating or cooling equipment.  
  • There may be a single switch or two switches: one for heating and one for cooling. Make sure that the power is on for both, then check your thermostat.
  • After you check the power, go to your thermostat and check if it’s working.

 

Verify the thermostat wires: 

 

Check that your system’s wires are in the right connector. It's important to protect yourself, your thermostat, and your system. Turn off power to your system and thermostat at the breaker or fuse box before exposing or adjusting any wiring.

 

  • Pull off the thermostat display.
  • Check that the wires are inserted correctly in the thermostat.
  1. Check that each wire is fully inserted into its connector and that every connector with a wire is down. 
  2. Check that each wire has ⅜ inch (6 mm) of exposed wire.
  3. Check that each wire is connected properly to the system board.

 

  • Put the display back on the base and turn the power to your system back on.
  • Check if your thermostat is working. If it still doesn’t work, check that your system wires are connected to the right connectors. Use the wiring diagram the app gave you during setup to move the wires to the right connectors. If you don’t have the wiring diagram, refer to this article to Identify a thermostat wire. 
  • Turn power to your system back on at the breaker or fuse box.

 

If you’ve tried the steps above and your thermostat still isn’t working, contact a local professional. 

 

Let me know if you have any other questions.

 

Best regards,

 

Daniel. 

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