If your Google Nest Learning Thermostat isn't controlling your HVAC system, the learning feature isn't working, or you're seeing error codes, this guide covers the most common problems and solutions.
Thermostat Not Turning On HVAC System
When your heating or cooling won't start:
- Check that the thermostat display is on and not showing any error codes
- Verify the system is set to the correct mode (Heat, Cool, or Heat/Cool)
- Ensure the target temperature requires the system to run
- Check if "Time-to-Temperature" shows the system is working toward the goal
- Look for a blinking red light on the thermostat indicating a wiring issue
- Check your circuit breaker and HVAC power switch
Auto-Schedule and Learning Not Working
If the Nest isn't learning your preferences:
- Verify Auto-Schedule is enabled in Settings > Auto-Schedule
- The thermostat needs about a week of manual adjustments to learn patterns
- Make consistent manual changes at the same times daily
- Check that Home/Away Assist isn't overriding your schedule
- Review and delete any incorrect schedule entries in the app
- Reset the schedule and let it re-learn your preferences
Error Codes on Display
Common Nest error codes and their meanings:
- E73 - No power to Rc wire. Check your HVAC system is on and wiring is correct
- E74 - No power to Rh wire. Verify heating system wiring and transformer
- E195/E196 - HVAC not responding. Check equipment connections and circuit breakers
- W1/W2/W3 - Wiring warnings. Review wiring against the Nest wiring diagram
- No power - C-wire issue. Install a C-wire or Nest Power Connector
- Contact Nest support for error codes not listed here
Battery Draining or Low Battery Warning
The Nest thermostat charges through your HVAC system:
- Check if you have a C-wire connected for continuous charging
- Without a C-wire, the Nest charges during heating/cooling cycles
- Install the Nest Power Connector if you don't have a C-wire
- Verify your HVAC transformer provides adequate voltage (20-30V AC typical)
- Try charging the thermostat off the base with a USB-C cable
WiFi Connection Issues
If the thermostat keeps disconnecting:
- Check WiFi signal strength in Settings > Technical Info > Network
- Move your router closer or add an extender if signal is weak
- The Nest works with both 2.4GHz and 5GHz networks
- Restart your router and the thermostat
- Forget the network and reconnect with correct password
- Check if router MAC filtering is blocking the device
Temperature Reading Is Inaccurate
When the displayed temperature doesn't match actual room temperature:
- Allow 30 minutes for the thermostat to adjust after installation
- Ensure the thermostat isn't near heat sources or in direct sunlight
- Check for drafts from doors, windows, or vents nearby
- Use a separate thermometer to verify actual temperature
- Adjust the temperature correction in Settings if consistently off
- Clean the thermostat and ensure nothing is blocking airflow
Home/Away Assist Not Working Properly
If the thermostat doesn't know when you're home or away:
- Enable Home/Away Assist in the Google Home app
- Grant location permissions to the Google Home app on your phone
- Add all household members to your Google Home for accurate detection
- Check that phone presence sensing is enabled for each member
- The built-in motion sensor takes about a week to learn activity patterns
- Adjust sensitivity settings if it's too quick to switch to Away mode
Factory Reset the Nest Thermostat
For persistent issues:
- Go to Settings > Reset > All Settings on the thermostat
- Or press the thermostat ring and hold for 10 seconds until the screen turns off
- Continue holding until "Nest" appears, then release
- Remove the thermostat from your Google Home before re-adding
- Set up the thermostat again from scratch