We installed a Nest Learning Thermostat 3rd generation in 2019 and intermittently had low battery warnings / wifi disconnecting, usually more often in spring and fall when the system ran less often. We do not have a C wire. We were going to pull new thermostat cable through the wall a few months ago to fix this, but then we looked into it and learned about the Nest Power Connector, so we bought and installed one of those, but we still get the low battery / wifi disconnect.
I then thought maybe the battery was dead due to the inconsistent charge for so long (or a malfunction), so I bought a new Nest Learning Thermostat 3rd generation from Costco (and I'll return whichever one doesn't end up working). It initially worked great, but then I got the wifi disconnect / low power thing again. When we installed the power connector, there were 2 wires going into Y, and I only put one of them on the power connector and I left the other on the control panel at the furnace. That didn't work. I then switched the wiring so that both Y wires are on the power connector, and that didn't solve the issue.
The battery charge at the thermostat when this is happening is consistently around 3.7 V.
The only other thing I can think of is that there is also a humidifier connected to the c terminal on the control board at the furnace. We don't use it - could it somehow be drawing power and making it so the Nest power connector doesn't get enough power to send to the Nest Learning Thermostat? Should I try disconnecting that from the c terminal? Or do you have any other ideas of what might be going on? Thanks in advance for your help!
