Troubleshoot strange heating or cooling behavior

1. Open the Home app .
2. Touch and hold your thermostat's tileEnergy dashboard .
3. Select Day, Week, or Month.

 Nest app

1. Open the Nest app and tap your Nest thermostat on the home screen.
2. Tap History  for a 10-day summary.
3. Tap on any day to learn more details about why the temperature changed.

On your thermostat

• Nest Learning Thermostat: Open the Quick View menu, then select History .
• Nest Thermostat E: Go to Settings History.

Learn more about Thermostat Energy History.

If you checked the symptom lists in step 1 above and your symptoms match, here are some troubleshooting steps you can take.

Wiring issues usually occur when you’re first installing a Nest thermostat. However, they can surface later as well, but usually for different reasons.

Turn off power to your system at the fuse box or system switch. This will help prevent damage to your system and help keep you safe. Pull off the Nest thermostat display. Check that all connectors that have wires are down (see picture).  If needed, re-insert wires so that the connector button stays fully pressed down. If the button isn’t down, your Nest thermostat won’t know there’s a wire in the connector.  You may need to re-strip and straighten the wire ends so that they can be fully inserted into the Nest base’s connectors.

Some common symptoms indicate that your system may need professional maintenance:

• Your Nest thermostat screen turns blue when you want cooling or orange when you want heat, but your system doesn’t turn on. 
  • Note: When your thermostat’s screen changes color, it’s trying to turn your system on.
• Your system works normally for a while after you restart it but one or more odd behaviors listed above in this article’s introduction eventually return.

To diagnose possible system maintenance issues yourself, you can install your old thermostat and test your system. This will help you tell if there’s a maintenance problem with your system, or if your system simply isn’t providing enough power to your thermostat.

1. Turn off power to your system at the fuse box or system switch.This will help prevent damage to your system and help keep you safe.
2. Uninstall your Nest thermostat.
3. Connect your old thermostat. Use the picture you took of your old thermostat’s connectors during the installation of your Nest thermostat to help you know where each wire should go on your old thermostat.
   • If your system works correctly with your old thermostat re-installed, then there may be a wiring or power issue with your Nest thermostat installation. You may need a common (C) wire or the Nest Power Connector installed. You may be able to connect an existing C wire or install the power connector yourself, but contact a local professional to install a new C wire and troubleshoot any other issues.
   • If your system doesn’t work correctly with your old thermostat and you see the same issues you had with the Nest thermostat, your system may need maintenance. Contact a local professional to diagnose and fix issues with your system.

If you connected a Nest thermostat to an incompatible system you'll likely experience unexpected behavior. While Nest thermostats work with most 24V systems, there are some system types and some specific models from various manufacturers that are incompatible. Others may need to have a C wire or the Nest Power Connector connected to be compatible. Go to the following article for a list of system types that aren’t Nest compatible.

Systems and hardware that aren’t compatible with Nest thermostats

Pull off your Nest thermostat’s display and check if there’s a wire in the C connector.

If there’s already a wire in the C connector 

Sometimes the wire in your Nest thermostat’s C connector isn’t properly connected to your system or your thermostat.

• Double check that all wires are in the right thermostat connectors. Use your thermostat wiring diagram and the picture you took of your old thermostat’s wires.
• If your thermostat won't turn on, go to our troubleshooting power issues article.
• If there's an error code or wiring report on your thermostat, go to our troubleshooting error codes article.
• If you’re still having issues with a wire in your thermostat’s C connector, contact a local professional to diagnose your system and check that your C wire is installed correctly.

If there isn’t a wire in the C connector

Check if there’s a C wire connected to your system’s board that you can connect to your thermostat.

1. WARNING: High voltage
   Be sure to turn off power to your home at the breaker, fuse box or system switch to protect yourself and help prevent damage to your system. Your furnace may be in a less accessible place like an attic or basement.
   • If you're comfortable accessing your furnace safely and you’re certain you’ve turned off power to your whole home, here are a few steps you can take.
   • If you're not sure that you can safely access your furnace, contact a local professional in your area to help troubleshoot your issue.
2. Look at which wires are connected on your system’s control board to see if any of them are connected to the system’s C terminal. If so, you can put the other end of that wire in your Nest thermostat’s C connector to see if the strange heating or cooling behaviors stop.
3. If there isn’t a wire in the system board’s C terminal, continue to the next steps. You can install the Nest Power Connector or have a professional HVAC technician, such as a local professional, install the power connector or a C wire for you.

A local professional can install the Nest Power Connector or a common wire if you don't have one already. They can also diagnose and fix issues with your system and check that your Nest thermostat is working properly.

• If you have a spare wire behind your thermostat that’s not connected to your system, your local pro may be able to use it as a C wire, which is usually cheaper than running a new wire to your thermostat.
• If you don’t have a spare wire, a local pro may be able to install the Nest Power Connector. It can provide power to your thermostat instead of a C wire. Typically, this is easier and less expensive to install than running a new C wire from your system to your thermostat.
• Your local pro may also be able to run a new wire from your system to your thermostat. Costs can vary depending on how difficult running the new wire will be. Ask your pro for an estimate.

Contact a local pro

Note: Pros are independent companies or contractors that Nest works with to help you install your Nest products. Although they are not employed by Nest, we try to maintain a network of well-rated installers for our customers to work with.