Start with weak airflow
A heavily loaded filter, blocked return, closed supply vents or blower problem can reduce cooling and contribute to coil freezing.
Look for ice or water
Ice on the line or indoor coil indicates a condition that needs attention. Turn cooling off rather than forcing the system to run.
Compare indoor and outdoor operation
Note whether the indoor fan and outdoor unit are each running. That observation helps narrow electrical, control and equipment possibilities.
Know when to stop
Shut the system down for burning smells, smoke, repeated breaker trips, spreading water or severe mechanical noise.
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.