No Cool
Ecobee Thermostat
Severity: ModerateWhat Does This Error Mean?
Ecobee 'No Cool' is an alert posted to the Alerts panel when the thermostat called for cooling, the system ran, and the indoor temperature did not drop within the expected time.
The thermostat itself may be fine — the alert points at the cooling equipment.
Cause is usually a tripped breaker, a frozen evaporator coil, low refrigerant, or a contactor that did not engage.
Affected Models
- Ecobee Smart Thermostat Premium
- Ecobee Smart Thermostat Enhanced
- Ecobee SmartThermostat with voice control
- Ecobee3 lite
- Ecobee3
Common Causes
- Outdoor unit breaker tripped
- Evaporator coil frozen — usually low refrigerant or dirty filter
- Outdoor contactor stuck open
- Capacitor failed — outdoor unit hums but does not start
- Refrigerant low from a slow leak
- Air filter so clogged that no airflow reaches the coil
How to Fix It
-
Check the outdoor unit.
Walk to the condenser outside.
If you hear nothing when the thermostat calls for cool, the outdoor unit is not running.
Check the breaker and the outdoor disconnect (the small gray box on the wall near the unit). -
Replace the air filter.
A clogged filter starves the indoor coil of air, the coil freezes solid, and cooling drops to zero.
If the filter is grey and matted, replace it.
Then turn the system off for 4 hours to let the coil thaw before retrying. -
Look for ice on the indoor coil.
Open the air handler or furnace door (if accessible).
If you see white frost or ice on the copper coil, the coil is frozen.
Run the system in Fan Only mode for several hours to thaw before calling for cool again. -
Listen at the outdoor unit.
If the unit hums but does not spin, the start capacitor failed.
Capacitors are 15-40 USD and easy to replace, but always discharge them first — they hold lethal voltage.
If you are not comfortable, an HVAC tech swap is 100-200 USD. -
Schedule refrigerant check.
If the system runs but barely cools, refrigerant is likely low.
This requires a licensed HVAC tech with gauges.
Refrigerant is not 'used up' in normal operation — low charge always means a leak that needs to be found, not just topped up. -
Dismiss the alert.
Once the system is repaired, open the Alerts panel on the thermostat or in the app and dismiss the No Cool alert.
It does not auto-clear after the system runs again — you have to acknowledge it manually.
Frequently Asked Questions
Why does Ecobee notice before I do?
Ecobee compares the actual temperature drop against what the system should achieve over a window of time.
A failing system often loses cooling capacity gradually — the thermostat catches the trend before you feel it indoors.