AC not cooling your home: what to check before calling

Start with the settings and airflow. Warm air alone doesn't tell you what's broken.

The answer in 2 lines. Check that the thermostat is set to cooling, with a temperature below the room reading. Inspect the user-accessible filter and make sure furniture isn't blocking return grilles. Look at the outdoor unit from a safe distance for an obvious obstruction. If you see ice, stop cooling and arrange service if the problem persists. Don't buy a recharge kit or open equipment panels. During dangerous heat, move to an air-conditioned place instead of waiting beside a broken system.

Start with these checks

Check the controls. Select Cool rather than Heat or Fan. Check the displayed temperature, schedule and batteries if the thermostat uses them.
Inspect the filter with the system off. Replace a disposable filter with the specified size and type; wash a reusable filter only as the equipment instructions allow.
Look for blocked airflow. Move furniture away from return grilles and remove loose objects around the outdoor unit without reaching through its guard.

Stop: danger

Smoke, sparks or suspected electrical fire: get everyone outside and call 911. Don't delay evacuation to investigate the equipment.
A breaker trips repeatedly: leave the system off and have the fault checked. Repeated resets don't fix an electrical problem.
Dangerous indoor heat: move to an air-conditioned location. Confusion, slurred speech or loss of consciousness can indicate heat stroke: call 911 and begin cooling the person while help comes.

Match the symptom to the next safe step

The display is blank: check batteries if applicable and look for a household power outage. Don't open the thermostat wiring compartment.
Airflow is weak: inspect the filter and accessible grilles. A clean filter doesn't rule out a blower or duct problem.
Air moves, but stays warm: confirm cooling settings. If the outdoor unit appears inactive while cooling is requested, record what you see and call for service.
Ice appears on tubing or the indoor coil: stop cooling. Restricted airflow can freeze the coil; low refrigerant is another possibility. Don't chip ice away or heat it with a tool.
Some rooms cool while others don't: note which rooms are affected. Ask the technician to assess air distribution before recommending replacement equipment.

What not to do

Setting the thermostat much lower to force a struggling system to recover.
Running cooling while ice continues building up.
Opening the outdoor electrical compartment, touching capacitors or pushing a stopped fan.
Adding refrigerant without finding out why performance has declined.

What to ask the technician

Send the equipment model, thermostat setting, any error message, photos of visible ice and a description of the airflow. Explain whether the problem started suddenly, followed maintenance or affects only part of the home. Ask for a written diagnosis and an estimate identifying the proposed repair.

For refrigerant work, use the EPA certification requirements to understand the credentials, then ask the technician to show the appropriate certification. This credential concerns refrigerants; contractor licensing requirements depend on your state and locality.

Renting, maintenance and staying cool

Renters should notify the landlord or property manager in writing, describe the indoor conditions and keep a copy. Repair duties, required cooling and available remedies vary by state, locality and lease. Use USAGov's tenant-rights page and follow its state-agency link to find the rules before withholding rent or arranging repairs you expect the landlord to reimburse.

For maintenance planning, open the Department of Energy home-cooling guide and read its maintenance section alongside your equipment instructions. Don't apply a universal filter schedule to every system.

During a heat emergency, use the CDC heat guidance to review protective actions and options for finding a cool location. Close sun-facing shades while arranging somewhere safer to stay.

Good to know

Ice is a symptom, not proof that the system needs refrigerant.
A dirty filter can reduce cooling and contribute to coil freezing.
If cooling returns after a filter change but ice or poor performance comes back, arrange a diagnosis rather than repeating the same workaround.

Illustrative example: In Dallas, Maya notices weak airflow and ice on an exposed refrigerant line. She stops cooling, replaces the dirty disposable filter and photographs the ice without opening the cabinet. When the problem returns, she sends the photos to a qualified technician and requests an airflow and refrigerant-system diagnosis.

A made-up story, for illustration.

Bobby

Sources, verification, confidence

Verified on November 5, 2026, for the United States. Confidence: high for basic maintenance, refrigerant certification and heat precautions; medium for symptom-based troubleshooting. A site inspection is needed to confirm the fault. Rental requirements vary by location.