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Error code E74

Mikeniekia1
Community Member

‎03-25-2026 07:17 PM

My Nest Thermostat 3 Gen stop working and displayed a E74 (no power to the RH wire) error code. The battery was dead, I charged it up, checked the RH wire's connection, checked the power source, and everything is good but the error is still there. I need the community's knowledge and experience to solve this problem. Thanks all! 

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Derickf
Community Specialist
Community Specialist

‎03-29-2026 04:50 PM

Hi @Mikeniekia1,

 

Thank you for posting in the community. I’m sorry to hear that you're seeing the "E74" error code on your Nest Learning Thermostat (3rd gen). I understand how important it is for you to have your device working properly. I appreciate you sharing the troubleshooting steps you've already taken, such as charging the battery and verifying the power source and wire connections. I'm happy to assist you.

To gather the necessary information, please answer the following questions:

  • How long did you charge your thermostat via USB before reconnecting it to the base?
  • Have you recently experienced any power outages or electrical surges in your home?
  • On your thermostat display, please go to Settings > Technical Info > Power. What are the current readings for Battery, Voc, Vin, and Iin?

I'll be waiting for your reply.

 

Best regards,

Derick

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