Nest Thermostat E72 error

[iggy99]

I am getting error 72 message on the Nest learning thermostat.  The thermostat is telling me it is not receiving power on RC wire.  All wires are properly seated and connected. The unit is running and the AC is cooling (i feel cold air from the AC duct and the room is cool); however, I can not set the temperature or go to settings or any other functions on the thermostat.  What is going on??

[luciaaa]

Hi, @iggy99,

Thank you so much for posting in the community. I’m truly sorry you are receiving an E72 error code on your thermostat. I’m happy to help you and find a solution. 

To effectively help you, please let me know: 

• Would you mind sharing a photo of your wiring configuration?
• Do you have a conventional or a heat pump system?
• When did your system last receive a professional maintenance check?
• When did the issue start?
• Did you experience any power outages recently?
• Is the display turning on? 
• When you remove the display, is the AC still running? 

While we gather more details, please try these troubleshooting steps:

Important: Before you begin, turn off the power breaker to your HVAC system.
 

1. Remove the display from the base plate.
2. Take a clear photo of the wiring configuration.
3. Carefully remove all wires and clean them with a dry towel.
4. Reinsert the wires as shown in the photo.
5. Restore power to the HVAC system and reattach the display.

Additionally, check the following:

• Check if your system’s drip pan or drain tube is full of water or has a clog.
• Ensure the air filter is clean. Replace it if necessary.
• Verify that the system's fuses are intact.

Please let me know how it goes.

Best regards,

Ana.