When an air conditioner runs but the house will not cool down, the cause is often simple, and a few safe checks can either fix it or tell the technician exactly where to start. Anything involving refrigerant, the electrical components inside the equipment, or a gas furnace belongs to a qualified technician.
1. Confirm the thermostat is calling for cooling
- Set the mode to Cool and the fan to Auto rather than On. With the fan set to On, the blower runs between cooling cycles and the air from the vents can feel warm.
- Set the temperature a few degrees below the room temperature and give the system several minutes.
- Replace the batteries if the display is dim or blank.
2. Check the air filter
A clogged filter restricts airflow across the indoor coil. Low airflow reduces cooling and can let the coil freeze. If you cannot see light through the filter, replace it, and note the size printed on the frame so the new one fits without gaps.
3. Check the breakers
The outdoor unit and the indoor air handler or furnace are usually on separate breakers. If the indoor fan runs but the outdoor unit is silent, look for a tripped breaker. Reset a tripped breaker once. If it trips again, leave it off and call: a breaker that keeps tripping is protecting something.
4. Clear the outdoor unit
The outdoor unit needs open airflow. Clear leaves, grass clippings and plant growth from around it and keep shrubs trimmed back. With the power off at the outdoor disconnect, a gentle rinse with a garden hose is fine; a pressure washer will bend the coil fins.
5. Watch for ice
Ice on the refrigerant lines at the outdoor unit, or frost on the indoor coil, means the system is short on airflow or refrigerant. Turn cooling off, leave the fan running to thaw the coil, and check the filter. If the ice comes back after the filter is replaced, call — running a system that keeps freezing can damage the compressor.
When to stop and call
- A breaker trips again after one reset.
- You hear grinding, screeching or loud buzzing from the outdoor unit.
- Ice returns after a filter change.
- Water is pooling around the indoor unit or the condensate drain has backed up.
- You smell burning or anything electrical.
Why our summers are hard on air conditioners
Long humid stretches in the Ohio River valley keep systems running for hours, and humidity adds load on the indoor coil and the condensate drain. Equipment that is the wrong size, or connected to leaking ductwork, shows its problems on the hottest, stickiest days first. A spring maintenance visit catches most of these problems before the first heat wave.
If these checks do not solve it, request HVAC repair and tell us what you already checked — it shortens the diagnosis. For a maintenance rhythm, read how often to service HVAC in the tri-state area.