The exposed part of the wire should be clean, straight, and 3/8” (1 cm) long. Cut and re-strip any crooked or corroded wire ends. Pull your thermostat off its base and remove both batteries. Make sure that nothing is between the battery and the battery terminals. You should fix any issues with your system or thermostat, but as a temporary measure, you can charge your Nest thermostat with a USB cable. However, if the old thermostat works perfectly with your system, your Nest thermostat might be seriously damaged.

If there's noblinking red light, it's possible that you’ve put wires into the wrong thermostat connectors. Make sure you've entered your system’s wires correctly into theapp and follow the wiring diagram it gives you.

If you have a Nest thermostat model that uses AAA alkaline batteries, replace them with a fresh set of the same batteries. Proprietary Heating System: If your HVAC system only has 2 wires when you have both heating and cooling systems, your heating system is most likely proprietary. The displays and bases of various thermostat models are not interchangeable, even though they may look similar. WARNING: Any attempt to connect low and high voltage thermostat parts may damage them as well as your system. Do not mix and match these bases and displays, even if the thermostats are the same model and generation. The 3rd genNest Learning Thermostat’s stainless steel ring can also be in different colors. If you have a thermostat ring that looks likeone of these, you have a 3rd gen Nest LearningThermostat.

If your Nest thermostat screen remains blank after trying other fixes above, there might be a blown fuse in your HVAC system. You can ask a professional installer to fix this issue for you. The installation expert will inspect your thermostat’s wiring and HVAC system and repair any faults. Try Using Your Old Thermostat Reinsert the wire. The connector button should stay down. If it’s not, the wire isn’t fully inserted. Repeat the above steps with each wire. Put the other end of the USB cable in a charger and plug it into a power outlet. Avoid using a computer to charge your Nest thermostat. If you don’t want to hire an installation expert to set up your Nest thermostat for you, you can call the Google Nest support team. They’ll walk you through the installation process and ensure that you set up the thermostat properly. Closing Thoughts If your system works as it should with your old thermostat, your Nest thermostat may be damaged and needs to be replaced.

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To help you identify whether your heating system is a high voltage, millivolt, or proprietary, we’ll try to describe them: Note that your Nest thermostat may charge for about an hour, especially if the battery is very low. If your Nest Thermostat won’t turn on, the batteries could have drained or there could be a power issue. If your system works with your old thermostat, try getting a professional to installyour Nest thermostat.Make an appointment with our installation partner OnTech, to have a trained pro come to your home, install and set up your Nest products.If your Nest thermostat is damaged, or if you need a professional to service your system, the installer maylet you know. Important: Turn off power to your system at the system switch or fuse box. This helps protect your system and thermostat from possible damage.