Nest Thermostat Not Cooling
Nest Thermostat Not Cooling
If your Nest Thermostat is showing not cooling, this guide covers the most common causes and the checks you can safely carry out before contacting support.
Nest Thermostat Problems — all models
What This Problem Means
This issue prevents your Nest Thermostat from functioning normally and may require troubleshooting to resolve.
Common Symptoms
• Air conditioning not activating
• Home not reaching set cool temperature
• Thermostat shows cooling but system not running
• AC unit not receiving signal
Safe Checks You Can Try
Check thermostat is calling for cooling
1. Set the target temperature below current room temperature
2. Check the display shows the cooling symbol is active
3. Listen for the AC unit to start within 2 minutes
4. Check the AC unit power switch and circuit breaker
Check O/B wire configuration
1. Heat pump systems use an O/B wire to switch between heating and cooling
2. Go to Settings then Equipment in the Nest app
3. Check whether O/B wire is configured as O (cooling) or B (heating)
4. Incorrect configuration causes cooling and heating to be reversed
Check system power
1. Verify the circuit breaker for your AC system has not tripped
2. Check the outdoor AC unit is powered on
3. Inspect the air filter and replace if blocked
4. A blocked filter can cause the AC system to shut down
Restart the thermostat
1. Press and hold the thermostat ring for 10 seconds until it restarts
2. Wait for the display to reload
3. Set a cooling temperature and test
4. Check the Nest app for any error messages after restarting
If You Need Spare Parts
If you’re confident carrying out the repair yourself, replacement air filters are available on Amazon with next day delivery.
Always check your model number before ordering to ensure compatibility.
When To Contact A Professional
If cooling still fails after these checks, contact a qualified HVAC engineer to inspect the AC system and wiring.
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