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Error E448 - No System Power HVAC Unit Still Running

Ewat33
Community Member

a week ago

I upgraded to the Nest 4th generation last year and have had no problems until last night. We had a big storm, lots of lightning, and I noticed this morning that our AC unit never shut off last night.  When I checked the Nest thermostat , it was showing offline with an error code E448. 

I checked all the breakers and even replaced the fuse on the HVAC unit but the thermostat still shows no power. The wiring plate is also not lighting up.

I needed to be able to control the air somehow so I decided to try an inexpensive, non-programmable thermostat and it is working fine. Not sure why it is working but the Nest is not. 

Any suggestions would be greatly appreciated. My upstairs AC went out in the storm as well so trying to not have to pay to repair both. 

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1 REPLY 1

kcruzgonzalez
Community Specialist
Community Specialist

Friday

Hi @Ewat33 ,

 

Thank you for posting in the community. I understand your Nest Thermostat (4th generation) is offline with error E448 after a storm, and your AC unit isn't working with it, though a traditional thermostat works fine. I'm here to help you investigate.

The E448 error code on a Nest Thermostat typically indicates that the thermostat isn't receiving consistent power. The fact that your wiring plate isn't lighting up and a simple, non-programmable thermostat works suggests that power is indeed reaching the HVAC system, but possibly not in a way that the Nest Thermostat can utilize or detect consistently after the electrical disturbance from the storm.

Given that your traditional thermostat is currently working, let's try a full factory reset of your Nest Thermostat. This can often resolve unexpected behavior or software glitches that might occur after a power surge or disruption.

Here's how to factory reset your Nest Thermostat:

  1. On your Nest Thermostat's display, go to Settings (gear icon).

  2. Scroll down to Reset and select it.

  3. Choose All Settings or Factory Reset.

  4. Confirm your selection. This will erase all settings and restore the thermostat to its original factory state.

After the factory reset, you will need to set up your Nest Thermostat again from scratch using the Google Home app. Follow the on-screen instructions on the thermostat and in the app to reconnect it to your Wi-Fi and configure your HVAC system.

Please tell me if performing a factory reset and setting it up again resolves the issue. I'll be here to assist you further if needed.

 

Regards,

Kevin

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