topic Re: Nest Thermostat 4th Gen Running Out of Power - Need Help! in Nest Thermostats

Nest Thermostat 4th Gen Running Out of Power - Need Help!

Smitty2 — Sun, 26 Oct 2025 17:32:15 GMT

I own two 4th Gen Nest Thermostats. One of the two units periodically shows the power status as "Power Savings". It will start turning features off like far sight and wifi. Eventually it runs out of power and needs to be recharged. The other unit has no issues.

Both units have a Common wire and should be continually charged. I'm unclear why the one keeps running out of power.

The working unit shows a Lin of 300. The problematic unit shows a Lin of 0 (WY).

Nest Support was useless and told me this was "Eco Mode" - 😂. I asked for a manager and they disconnected from our chat. Great service - what a joke. (Case ID 6-5139000040522 if someone from Google can contact me).

My questions for this group:

1. Should a unit with a common wire and continuous power require charging periodically? If so, did something change with 4th gen (3rd gen didn't require us to do this)?

2. What does a "Lin" of "0 (WY)" mean?

3. How can identify if the common wire set up is working? I've tested with a multi-meter and get the correct voltage across the Rc and C wires from the AC unit.

Thanks for the help! Only wish Google could've answered these questions.

Re: Nest Thermostat 4th Gen Running Out of Power - Need Help!

CoolingWizard — Sun, 26 Oct 2025 18:28:01 GMT

The second unit does not see the common wire. As a result the thermostat is trying the W and Y wires in attempt to reach the Common Power.
Check you Common wire using a multimeter set to AC Voltage. Put one lead on the C wire and the other on the R wire. Report the voltage seen

The Cooling Wizard

Re: Nest Thermostat 4th Gen Running Out of Power - Need Help!

Smitty2 — Sun, 26 Oct 2025 18:56:39 GMT

Thanks for the quick response. That makes sense now.

It's showing 27 volts across the C and Rc wires.

I took my other nest 4th gen display and put it on the baseplate that has the issue. It correctly recognized the common wire (showed Lin of 300). So it seems to be something with the display unit.

When I go into the wiring config on the failing unit it shows the C is configured. Are there other settings I need to change to get it to use the common wire?

Re: Nest Thermostat 4th Gen Running Out of Power - Need Help!

CoolingWizard — Mon, 27 Oct 2025 05:02:53 GMT

@Smitty2 ,

This sounds like you need to submit a warranty request for the defective displau.

The Cooling Wizard