Nest 3rd Gen Learning Thermostat

[Jazzdrum57]

Nest 3rd Gen Learn Thermostat has been working perfectly for several years.  It went offline today and now can’t find my network.  Went through all the steps including restarting the router to no avail.  All other devices on the network are working including the upstairs Nest thermostat.  Any ideas on how to fix it?

[Paul48312]

I had a similar problem. Working fine for years then heating went erratic, cycling on and off rapidly and message stating not enough power for WiFi and showing offline in the app. Solution was to connect a C wire. Since I have a four wire system I used the G wire (fan) and placed it on C. Also did the same on my furnace control board. Heating now works correctly, no messages and connected to network. 

[Paul48312]

It puzzles me why it worked perfectly for years on a 4 wire config without a C wire. Now it needs a C wire. I read somewhere for configs without a C wire, the Nest scavenges power from the circuit when heating or cooling are active. I suspect a software update broke this feature causing my battery to drain and go into the bad operating state it was in. Glad I found a fix. 

[Foxholme2019]

I too only have a 4 wire connection. I’m kinda scared to mess with my furnace board though. What happens with the fan then if you moved it to the C wire?

[Paul48312]

The consequence is you don’t have the ability to set the Nest to fan only mode ( run the fan without heating or cooling). I’m ok with this because I don’t use fan only mode. Also, the heating and cooling modes will control the fan as needed. 

The alternatives are 1) replace 4 wire with 5 wire or 2) install the Nest power module. These 2 options add expense and are more effort than above. 

[Copycat1]

Does anyone have a fix for this problem? I have the problem too.

[Paul48312]

Do you have the C wire connected on the nest and on your furnace? If not, connect it up and then try to reconnect to WiFi. 

[Jazzdrum57]

I do not have a C wire.  It is only a 4 wire system.  When this problem occurred, the system was off.  

[Paul48312]

I also have a 4 wire system. What I did was to use the G wire (typically for fan control) and put it on C at the Nest and furnace control board. Now I have full power and everything works. Note with this solution I can no longer control the fan directly. I don’t care since the heating and cooling functions control the fan. 

The alternative is to replace the 4 wire with 5 wire to get full functionality including independent fan control, or buy the Nest power add-on module.

[Foxholme2019]

This is really helpful, I’m just nervous because I’ve never wired anything before. Hopefully I can locate the furnace control panel easily to move wires around. 

[Jazzdrum57]

Thanks for your advice.  I have a second unit upstairs with a 4 wire connection also and it continues to work fine.  I may switch the units and see what happens.  I don’t want the 2nd unit to stop working.  

[Copycat1]

yes, I have a blue wire connected to the "c" post.

[Paul48312]

Then you should not have a power issue. Confirm your network is running and devices can connect to it. Now use the Nest device, and select the gear icon, select Network, select the network name and enter password. See https://support.google.com/googlenest/answer/9223192?hl=en

[Foxholme2019]

I think I am also having a similar issue. Our furnace died and they replaced the motor. However it took a few days so the nest was offline and I did not know you could charge it. So the battery was drained. Plugged it in to a usb to charge and then put it back on the base. That was two weeks ago. 

Now it’s saying not enough power and I can’t figure out or understand why. 

[Paul48312]

You need to add a C wire. See other replies in this thread for details. 

[Jazzdrum57]

So I decided to purchase the Nest C wire adapter ($17.99 on amazon) and will connect it and see if the problem resolves.  It’s not an expensive test and if it doesn’t work I can return it for a full refund.  I’ll post my results.

[Jazzdrum57]

Got the C wire adapter today, connected it and the problem remains.  Honestly, I didn’t think that was going to solve the problem since I had no error message for the power.  I contacted Nest Tech support and ran through their tests to no avail.  Because the unit is out of warranty, there is no replacement available.  Thanks for your help.  Hope others find a solution.

[Paul48312]

Bummer. Sorry it didn’t work. Sounds like you’ll have to replace it with new. Good luck. 

[Markjosephp]

Hello everyone,

I know it has been a while, and I appreciate everyone's help here regarding the issues you're experiencing with your Nest Thermostats going offline despite attempting several troubleshooting steps.

Based on the information you've provided, it seems like you've already taken some proactive steps to troubleshoot the problem. However, there are a few additional steps we recommend trying to address the offline status of your Nest Thermostat:

1. Ensure that your Wi-Fi network is functioning properly and that there are no issues with connectivity. You can try restarting your router or moving the thermostat closer to the router to improve signal strength.
2. Make sure that your Nest app is up-to-date on your smartphone or tablet.
3. Verify that your router settings are compatible with Nest products. Some routers have specific configurations that may affect the connection stability of smart devices like Nest Thermostats. Refer to your router's manual or contact your internet service provider for assistance with router settings.

Please let us know if you have any further questions or if there's anything else we can assist you with.

Best regards,
Mark