Nest Thermostat *OB wire not detected

[Whonan]

Hey everyone, looking to get some assistance with this. 

i just installed a Nest thermostat (non learning) and it’s telling me that it cannot detect the *OB wires. It does detect everything else (Y, W, G, R), and I confirmed that the wire is clean and seated properly. When the heat is on, it just blows cool air. I also put the old thermostat back in just to make sure the wire still works, and it does. Heat returns to normal with the old thermostat, so it must be something with the Nest. Any ideas?

[moralesvicente]

Hi Whonan, 

Thank you so much for posting in this community. I’m sorry to hear that your Nest Thermostat is not detecting the cable O/B in the new wiring configuration. Don't worry; I would be more than happy to help. 

I appreciate that you have taken action by performing the troubleshooting steps above. To continue getting to the root of the issue, could you please help me by answering these questions?

• Do you see an error code or notification displayed on your thermostat? 
• Could you share a photo of your previous and current wiring setup? I’d like to take a look at how the wires are installed. 

Any additional details you can provide will be helpful.

Best regards,

Daniel

[Whonan]

Hi Daniel,

Here’s some photos of the old wiring, the Nest wiring, and the codes I’m seeing on the Nest. There is a “Note N260” error that shows up on the Home Screen.

 

 

 

 

 

[moralesvicente]

Hello Whonan, 

I'm grateful for the useful information provided. Checking your wiring system, it seems to be connected properly. However, verifying the error code displayed on your thermostat (N260) indicates that it requires a C wire or Nest power connector. 
 
You can fix the trouble by installing the Nest Power Connector or C wire. Either one will provide a stable power source for your Nest thermostat and deliver enough consistent power to your system.
The C wire is different from other wires. It doesn't control the temperature. Instead, it gives your thermostat the power it needs to work.

For your reference Here are some articles to verify what troubleshooting steps you can take regarding the error code: Troubleshoot Nest thermostat help codes.

Please let me know if these suggestions were helpful.

Regards,
Daniel