When your air conditioner runs but the house stays warm, it is tempting to panic and call for emergency service. Before you do, a handful of simple checks can sometimes solve the problem yourself, or at least tell you how serious it is.

Check the thermostat It sounds obvious, but confirm the thermostat is set to cool, not just fan, and that the target temperature is below the current room temperature. If it runs on batteries, replace them. A blank or frozen thermostat is a common culprit.

Replace a dirty air filter A clogged filter is the number one cause of weak cooling. When airflow is choked, the system struggles and can even freeze up. Pull the filter; if you cannot see light through it, replace it. Many homeowners are amazed how much this alone helps.

Look at the outdoor unit The outdoor condenser needs airflow to dump heat. Clear away leaves, grass clippings, and debris, and trim back any plants growing within a couple of feet. Gently hose off a dirty coil after cutting power to the unit.

Check the breakers The indoor and outdoor components often run on separate circuits. A tripped breaker can leave the fan running while cooling is dead. Reset any tripped breaker once; if it trips again, stop and call a pro.

Look for ice If you see ice on the refrigerant lines or coil, turn the system off and let it thaw. Ice usually points to airflow problems or low refrigerant.

When to call a pro If the basics check out and the air still is not cold, the issue is likely refrigerant, the compressor, or electrical components, none of which are DIY fixes. That is the moment to get matched with a licensed HVAC pro for a proper diagnosis.