Your thermostat erases some or all of its information depending on the option you choose. The thermostat will restore its factory default settings. When there is no power to your Nest’s Rh wire, it will show an E74 error code on the display, and your system will fail to turn on. The most common causes of this problem are:

If your system doesn’t have a C-wire or if it was already securely attached, you may need to charge your battery manually. The Nest Thermostat E and 2nd- and 3rd-gen Nest Learning thermostats can be charged using a micro-USB cable. For a 1st-gen Nest Learning Thermostat, you’ll need a mini-USB cable instead. If you have the Nest Learning Thermostat with a single transformer system, switch the power wire between the Rh and Rc terminals. A thermostat restart can fix some common issues. Reset your thermostat to clear your personal settings.After you reset the account connection, you'll still find your thermostat in the app. However, your thermostat will be listed as "offline" and you'll no longer be able to control it with the app. To remove it from your account and app, you'll need to go to your thermostat's settings.

As long as the thermostat base is from the same model, generation and country/region as the thermostat display, you can swap bases and displays.Give each of those fixes a chance to resolve your network problem before moving on. Interference problems are the next most likely culprit, especially if you’ve been adding more items to your network. Try shutting off devices and—if possible—moving the nest and router closer together to see if that fixes the connection issue. However, in systems without a C-wire, the Nest can only charge itself when the heating or cooling system is actively running. In the next section, we’ll go over the steps you can take if your Nest isn’t charging itself. 3. Nest Thermostat Battery Won’t Charge Alternatively, you could replace your Nest with an Ecobee system. Unlike Nest, Ecobee thermostats all include an adapter system for systems without a C-wire. But buying a whole new system is a pretty expensive fix compared to the add-a-wire accessory. 5. Nest Thermostat Delayed Your thermostat learns how often you walk by to help it know when to automatically switch to and from Eco Temperatures as you leave and come home. If you reset Home/Away on your thermostat, everything it has learned about when you're home or away will be reset. Since the C-wire is the preferred power source for Nest, a loose C-wire can cause the charging process to fail. If you tightened the C-wire during the above steps, give the system some time to charge before proceeding with your troubleshooting.

As with many Nest problems, blowing hot air on cool or cool air on hot is usually caused by a wiring issue. Specifically, it usually means that your system has a heat pump, but you’ve wired it to the conventional system row.If you need further help, or find a restart doesn’t fix the issue, go to our thermostat troubleshooter. Differences between restart and reset

Your thermostat can only read the temperature where it is located. Temperatures in other areas of your home may be significantly different. Adding a Nest temperature sensor to your system can help if you have a large home or if your Nest is located in a particularly hot or cool area of your home. The Failed to connect message or error codes M21 and M22 all mean that your Nest can’t connect to your Wi-Fi network. The problem could be with your thermostat or with your Wi-Fi network, so we’ll try a few fixes for each. Use this reset option if you move your thermostat to a new location in your home, or if you've had your home remodelled. Your thermostat will learn about its new location in a few days. The Nest app’s step-by-step instructions make it easy to install and wire your thermostat, so use it as your main guide. Refer to this article if you need extra help. The displays and bases of various thermostat models are not interchangeable, even though they may look similar.If your Nest doesn’t have charging issues, you don’t need to do anything. Your Nest must be getting enough juice on its own. Press and hold the screen for 10 seconds until it shuts down to refresh. (Nest Learning Thermostat and Nest Thermostat E) When your Nest thermostat says delayed, it is telling you that the system is underpowered. This often happens when Nest is run without a C-wire.