I have a Nest Learning Thermostat from 2018. It worked fine until this winter, but now it keeps losing power and going offline. I only use it for heat (propane furnace), no AC.
It’s been extra cold, and I’ve noticed that the thermostat shuts off for hours at a time and then comes back on. My WiFi is working fine, so that’s not the issue. Last time, I had to drive three hours to my house just to manually charge it, and it stayed on for a week after that, but now it’s happening again.
Could it be that the battery is failing? Do I need a C wire? I read that the thermostat doesn’t charge when heating is on—could that be the problem? I’ve also heard of power adapters, but I’m not sure if that would work for me.
It seems like the thermostat is getting some power, just not enough to stay on. Any advice on what I should do?
You should install a C wire or get a Nest power connector. Just replacing the thermostat won’t fix it long-term. A C wire will make sure the thermostat gets constant power and prevent this from happening again.
I also have a two-wire system for my propane boiler and never had battery issues for years. But one of my thermostats recently started dying every couple of weeks. I swapped it with another one and the issue followed the thermostat, so I replaced the battery, and it’s been fine since. If your setup worked since 2018, it might just be a bad battery.
@Jerry
If this is a second home and the heat isn’t running often, the battery might not be charging enough. Adding a C wire is the best solution to keep it powered at all times.
Check behind your thermostat wiring. A lot of homes have extra unused wires that could be connected as a C wire. I found one behind mine and hooked it up to my furnace, and it fixed my power issues.
You should get the Google Nest power adapter. It’s easy to install and works as a substitute for a C wire. You can find it on Amazon or Google’s store.
Order a Nest power adapter and a 24V transformer from Amazon. If you’re not comfortable installing it yourself, you can schedule a technician through Google.
Nest claims to work without a C wire, but in reality, all smart thermostats need one. If you have at least three wires in your bundle, you can use an add-a-wire kit instead of running new wiring. Check out something like the Venstar Add-A-Wire kit on Amazon.
Are you sure your WiFi is actually solid? Thermostats like the Nest resend data multiple times when the connection isn’t great, which drains the battery faster.
Smart thermostats really need a C wire. If you rely on battery power, you’ll eventually have to replace it or deal with the thermostat shutting down. Either run a C wire or get a power adapter to avoid future issues.
I had this same problem and added a 24V adapter to my Nest instead of running a C wire. Works perfectly. Much easier than using the Google Power Adapter, which needs to be installed at the furnace. Never buying another Nest thermostat though.