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Google Nest Learning Thermostat Gen 3 is not charging and seems to be losing battery fast.

VitoKuang
Community Member

‎12-13-2023 06:49 PM - edited ‎12-13-2023 07:18 PM

I have a Aprilaire 6202 HVAC control system that is dual zone with dampers. There are 5 wires (R, Y, W, C, and G). I have two nest learning thermostats for different floors. The install is only about 1 1/2 years old on a new construction home when the problem started happening. The weather is now colder, and the problem seems to start happening when we started using heat rather than cooling. This issue did not happen last winter though. The upstairs zone thermostat is not charging and seems to be losing battery fast. After using usb to charge it, it only lasts for about 2-3 days before shutting down from low battery.

 

I have tried swapping the downstairs and upstairs nests to isolate the problem and the issue seems to only occur in the upstairs zone. Both thermostats in both zones recognize all 5 of the wires. Both also are connected to wifi at all times and the only times not are when the upstairs one loses too much battery voltage. The 5 connections made are to W1, G, Rc, Y1, and C for both base plates.

From testing both nests connected to the downstairs zone I am seeing battery voltage of 3.8-3.9, Vin & Voc read ~33 V, and Iin is 200 mA.

The upstairs zone I am seeing battery voltage of 3.6-3.7 volt, Vin & Voc read ~37 V, and Iin is 200 mA.

 

In the HVAC control panel, I checked all of the voltages with a multimeter and from R to the other 4 wires I am seeing 27-28 V. I also tested the 24V transformer and the input is 122 V, and the output is the 27-28 V; I also tested the power into the control panel and the voltages are 27-28 V. I then also tested the connections at the thermostat backplates and read the same 27-28 volts from the R to the 4 other wires.

 

Are there any other things I can test to help narrow down the issue either with the furnace, control panel, or nest? I was thinking to swap the base plates as I am seeing they are different in the technical info. The upstairs is software version 1.5.38/3.1 and model is 5.4. The downstairs is software version 2.3.51/3.1 and model is 5.26. 

 

Thank you in advance for your help!

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2 REPLIES 2

VitoKuang
Community Member

‎12-13-2023 07:26 PM - edited ‎12-13-2023 07:37 PM

Here is an image of the furnace details. I also checked the fuse in the furnace and it was ok. 20231212_223302.jpg 

20231213_203536.jpg

 

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zoeuvre
Community Specialist
Community Specialist
In response to VitoKuang

‎12-18-2023 01:20 PM

Hi VitoKuang, 

 

Yikes! I'm sorry to hear your thermostat is not charging and seems to be losing battery fast. The issue appears to be specific to the upstairs zone and the Nest Thermostat installed there, and additional troubleshooting steps can be attempted to resolve the problem. A few questions: 

 

  1. Are you located in North America or Europe?
  2. Are the power breakers on, and do you receive power to your home?
  3. Is the thermostat's display seated properly?
  4. Are all the wires of your thermostat seated firmly in its terminals (with no loose or exposed wires)?
  5. Did you charge the thermostat display using a micro-USB cable?
  6. If so, does the micro-USB cable work with other devices as well?
  7. Did you plug in the thermostat display into a working power outlet?
  8. For how long did you charge the thermostat display?

 

Also, follow these: 

  1. Double-check the wiring connections at the upstairs Nest Thermostat and ensure they are secure and properly inserted. Make sure there are no loose or damaged wires. Pay particular attention to the C (common) wire connection, as a weak or intermittent connection could cause battery charging issues.
  2. To test the upstairs Nest Thermostat, use a multimeter or voltmeter to measure the voltage between the RC or RH wire and C wire. A consistent voltage of 27-28 V is ideal, but lower or fluctuating voltages may indicate a specific wiring or power supply issue.
    • Set the dial to 200 VAC.
      • If the multimeter doesn’t have a 200 setting, choose 100 or 250 VAC.
      • The general rule of thumb is don’t set it too high (500+) or too low (50). Place the red lead on the RH or RC wire.
    • Place the black lead on the C wire being tested.
    • The normal readout should be somewhere between 20 and 30 V (24 V is most common).
  3. Swapping base plates between upstairs and downstairs Nest Thermostats can help identify if the issue is related to the base plate or the thermostat itself. If the problem persists with the upstairs base plate connected to the downstairs thermostat, it suggests a possible issue with the base plate, while if it occurs with the downstairs base plate, it suggests a problem with the thermostat.

 

Working with electrical systems can be hazardous, so if you're unsure or uncomfortable with certain steps, it's advisable to seek professional help to safely diagnose and resolve the issue.

 

Let us know how it goes.

 

Best,

Zoe

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