🔄 Try this first — Press and hold the thermostat ring for about 10 seconds until the screen turns off, then release to restart it. Also check your boiler is switched on and your router is working.

Is your Nest Thermostat E not turning on your air conditioning or cooling system when it should? Here are the checks you can safely carry out before contacting support. Note that most UK homes do not have cooling connected to their thermostat — this guide applies if you have air conditioning wired to your Nest.

What This Problem Means

The thermostat is not successfully calling for cooling. This can be caused by a temperature setting, the system mode being set incorrectly, or a wiring or compatibility issue with your cooling system.

Common Symptoms

  • Cooling does not activate when the room is warmer than the target temperature
  • The system mode may be set to Heat only rather than Cool or Heat-Cool
  • The cooling symbol does not appear on the display
  • Air conditioning does not respond to the thermostat

Safe Checks You Can Try

1. Check the System Mode

On the Nest Thermostat E, go to Settings and check the system mode is set to Cool or Heat-Cool rather than Heat only or Off. If set to Heat, the thermostat will never call for cooling.

2. Check the Target Temperature

Set the target temperature lower than the current room temperature. Cooling only activates when the room is warmer than the target.

3. Check Your Cooling System Is Powered

Confirm your air conditioning unit is switched on at its own power supply and is not in a fault state. The thermostat cannot activate a cooling system that has no power.

4. Restart the Thermostat

Press and hold the thermostat ring for about 10 seconds until the screen turns off, then release to restart it. Allow it to restart, then test cooling again.

5. Check Cooling Compatibility

Not all wiring configurations support cooling. If your Nest Thermostat E was installed for heating only, the cooling wires may not be connected. A qualified HVAC engineer can confirm whether your system is wired for cooling control.

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When To Contact Support

If you have worked through the checks above and the issue persists, contact Google Nest support at https://support.google.com/googlenest. For heating system faults that do not resolve, consult a qualified heating engineer — the Nest Thermostat E works with your existing boiler wiring and a heating professional can check the connections safely.

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