AC fan runs but no cold air: what to check first

Safe checks you can do yourself

Confirm the thermostat is set to cool, not fan-only, and that the set temperature is below the room temperature. Replace or clean a clogged indoor filter. Blocked airflow can make the system blow room-temperature air and can cause the indoor coil to ice up.

Look at the outdoor unit if you can do so safely. The outdoor fan and the area around the unit should be clear of leaves, grass, and debris. Do not reach into the unit or remove panels. Check whether a circuit breaker for the air conditioner or furnace air handler has tripped, and reset it only once. If it trips again, stop and call a professional.

Open supply vents and make sure return-air grilles are not blocked by furniture or curtains. If you see ice on the copper lines or the indoor coil, turn the system off and leave the fan on if the thermostat allows it, so ice can melt. Running a frozen system can damage it.

When to call a professional

Call a technician if the simple checks do not restore cooling, if breakers keep tripping, if you smell burning or notice buzzing electrical parts, if the outdoor unit is silent while the indoor fan runs, or if you suspect a refrigerant leak. Refrigerant work is not a homeowner repair.

A system that ran out of refrigerant, has a failed compressor or capacitor, or has a control-board problem needs tools and training you should not improvise with. If anyone in the home is at risk from heat, arrange a temporary cooling plan while you wait for service.

Questions to ask the technician

Ask what they found, what tests they ran, whether the proposed repair is a failed part or a symptom of another problem, the cost of the diagnosis versus the repair, and whether a written estimate is available before work begins.

Ask about warranties on parts and labor, and whether a similar failure is likely if a related part is left as-is. You do not have to approve a full replacement on the spot. A second opinion is reasonable for a large job. Use a call log so you can compare what you were told.