Confirm the cooling call
Set the thermostat to COOL and below the current room temperature. Replace thermostat batteries only if the model uses accessible batteries.
Check visible power conditions
Note whether the thermostat display, indoor fan or outdoor unit has power. If a breaker has tripped, do not keep resetting it.
Look for water or a safety shutdown
Some systems stop when drainage protection detects water. Do not bypass a float switch or continue running equipment near spreading water.
Share exactly what is inactive
Tell the service provider whether the thermostat, indoor fan, outdoor unit or entire system is unresponsive and when it last operated normally.
When to request professional service
Request service when basic settings and an accessible filter do not explain the problem, or when the system is frozen, leaking, electrically unstable, unusually noisy or unable to maintain a safe indoor temperature.
Shut the system down for smoke, a persistent burning smell, repeated breaker trips, spreading water or severe mechanical noise. Call emergency services for fire, medical danger or another immediate threat to life or property.