AC Blowing Warm Air: Causes and What to Do

Check these first

Most homeowners can safely rule out the simple causes in a few minutes.

• Thermostat is set to Cool and the setpoint is below room temperature
• Fan is set to Auto, not On
• Filter is not clogged
• Breaker for the outdoor unit hasn't tripped
• Outdoor disconnect switch is on

Go outside and look at the condenser

With the system calling for cooling, the outdoor fan should spin and you should hear the compressor. If it hums but the fan doesn't turn, the capacitor or fan motor has likely failed. Turn the system off at the thermostat to protect the compressor.

Look for ice

Ice on the larger copper line or the indoor coil means airflow is blocked or refrigerant is low. Switch the thermostat to Off, set the fan to On to thaw the coil, and call for service. Running an iced system can damage the compressor.

When it's refrigerant

Refrigerant doesn't get used up. If it's low, there's a leak. A proper repair finds and fixes the leak, then charges the system to the manufacturer's spec, rather than just topping it off.

When to call

Call right away if the outdoor fan isn't running, the breaker trips again, there's ice, or the house is heating up during extreme heat. In Las Vegas summers, treat no cooling as urgent when vulnerable people are at home.

Questions