Learning thermostat goes into charging

[Bwdelano]

My thermostat constantly turns off and flashes it's red light for charging. I charged it via USB the other day and it worked for a short time but it's back to doing it again. I've checked the wiring (3 wire), and measured the power at the plate at 27V A/C. 

[MelbaDT]

Hey Bwdelano, 

Sorry to hear about your Nest thermostat but thanks for reaching out and for trying those steps already. I want to dig deeper into it. 

A few questions — was this just installed or did it work with this same HVAC system before? If it worked before, were there recent changes made on your wiring or actual thermostat device before this started happening? Also, how is your thermostat wired? 

Best, 

Melba

[Bwdelano]

I installed it just after Christmas, it had been working fine until about two weeks ago. I haven't made any changes to the wiring since I installed it. It's just a 3 wire red/white/green. There are other wires in a common jacket, but none were connected to the previous thermostat so I don't know if they're connected to the furnace.

I am a licensed electrician in Washington state, so I have testing equipment if you need other information, I've just never worked with HVAC so I don't know what I should be looking for with the system.

[MelbaDT]

Hey there, 

Sorry for the delay here but thanks for these added information. 

Could you provide a photo of how your thermostat is currently wired? Are you getting a code on the thermostat display when the battery drops? Also, could you try to remove the thermostat display from its base and check if any connector pins are bent? 

Best, 

Melba

[Bwdelano]

Hi.

No, I don't get an error code. Just a message that the battery needs to charge. I've included photos of the wiring and pins.

Wiring 

Pins 

[MelbaDT]

Hey there, 

Thanks for the photos and for these added details. Based on the wires of your thermostat, it is sharing power from the RH and W1 terminal. Could you try the following suggestions: 

• Check that your system is receiving power. 
  1. Try to turn off the breaker or switch that controls power to your system, then turn it back on again. Make sure the switch is pushed all the way to the On position.
  2. If you have a fuse box, check that the fuse controlling power to your system isn’t blown and is working normally. Replace it if needed.
  3. If your thermostat shows you a blinking red light, the battery is charging and it'll eventually turn on. It can take up to an hour if the battery is extremely low.
• Check your thermostat’s wiring.
  1. Pull the thermostat display off the base.
  2. Pull out one wire and inspect it. The exposed part of the wire should be clean, straight, and 3/8” (1 cm) long. Cut and re-strip any crooked or corroded wire ends.
  3. Reinsert the wire. The connector button should stay down. If it’s not, the wire isn’t fully inserted. Repeat the above steps with each wire.
  4. Once you've checked all the wires, push the display onto the base until you hear a click.
  5. Turn the system power back on.

You may also check this link for additional steps that you can try should the suggestions above won't work: https://bit.ly/3v3nwzX

Best, 

Melba

[MelbaDT]

Hey Bwdelano, 

It's me again — I wanted to ensure you've seen my last response above. Have you had the chance to try the suggested steps? If yes, how's everything now?

Best, 

Melba

[MelbaDT]

Hi, 

We haven't heard from you in a while so we'll be locking this thread if there is no update within the day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the Community.

Best, 

Melba