Google Nest Learning won't charge with Nest Power Connector

[Bruno28]

I have 2 Nest Learning thermostats at different addresses with the power connector installed at both - one works fine and has a regular charge at 3.8v+, the other drains rapidly at 3.6v.

I can still charge the 3.6v one via USB but as you can imagine the charge doesn't last long.

I measured the voltage at both the furnace control board and at the wires at the base.  Both are showing 26VAC but yet the unit isn't charging.

It's been doing this for almost 2 months now having bought the thermostat 11 months ago.  It was working great for 9 months until this happened.

I worked with Google Support and have a case number, but despite my showing the VAC readings they were convinced I have a millivolt system (I don't think I do - it's a Carrier furnace with a 24VAC board) and didn't help further.

Is there something I'm missing?  Would appreciate any help or direction to further diagnose.

Cheers, Bruno

[Bruno28]

Just an update.  I charged it via USB for 1.5hrs last night and the charge only lasted overnight.  Starting to wonder if there is something wrong with the thermostat itself.

[ByronP]

Hi Bruno28,

Thank you for posting here in the community. I'm really sorry that your Nest thermostat doesn't hold the charge. I understand how frustrating it is when you already try to charge it but it doesn't work. Help's here.

I just want to confirm a few questions before proceeding any further. Can you check any power error message on your thermostat display? Please follow the below steps:

Go to Settings > Technical Info > Power.

Please keep me posted. I'll look forward to your response.

Regards,

Byron