Why is my Google Nest blowing hot air on cool?

Answered by Robert Dupre

If your Google Nest thermostat is blowing hot air when it should be in Cool mode, there may be an issue with the wire settings for your heat pump. This can be easily resolved by adjusting the O/B wire settings on your thermostat.

The O/B wire is responsible for controlling the reversing valve in your heat pump, which determines whether it is in heating or cooling mode. If your system is blowing hot air when it should be cooling, it means that the reversing valve is not set correctly.

To change the O/B wire settings on your Nest thermostat, follow these steps:

1. Open the Nest app on your smartphone or tablet.
2. Select your thermostat from the list of devices.
3. Tap on the Settings icon in the top right corner.
4. Scroll down and select Equipment.
5. Choose the option for Reversing valve.
6. Depending on your thermostat model, you may see different options for the O/B wire. Select the one that matches your system’s configuration.
7. Save the changes and exit the settings menu.

After making these adjustments, your Nest thermostat should now properly control the reversing valve and blow cool air when in Cool mode. If you’re still experiencing issues, it’s possible that there may be a wiring problem or a malfunction with your heat pump. In such cases, it’s best to consult a professional HVAC technician for further assistance.

It’s worth mentioning that the specific instructions for changing the O/B wire settings may vary depending on the model of your Nest thermostat. The steps provided above are general guidelines, and it’s recommended to refer to the official Nest documentation or contact Nest support for detailed instructions tailored to your specific thermostat model.

If your Nest thermostat is blowing hot air instead of cool air, adjusting the O/B wire settings can help resolve the issue. By properly configuring the reversing valve, your thermostat will be able to control your heat pump’s operation correctly.