Troubleshooting
AC Running But Not Cooling: 8 Causes and What to Check
7 min read••
When your air conditioner runs constantly but fails to cool your home, several issues could be at play. This guide walks through the most common causes.
Your air conditioner is humming along, but your house feels like a sauna. This frustrating situation is one of the most common HVAC problems we encounter in Bay Area homes.
The Most Common Causes
1. Dirty Air Filter A clogged filter restricts airflow, forcing your system to work harder while delivering less cooling. Check your filter first—if you can't see light through it, it needs replacing.
2. Frozen Evaporator Coil Restricted airflow or low refrigerant can cause ice to form on the indoor coil. If you notice ice buildup, turn off the AC and let it thaw before calling for service.
3. Dirty Condenser Coil The outdoor unit needs clear airflow. Debris, leaves, or dirt on the condenser coil reduces its ability to release heat. You can gently rinse it with a garden hose.
4. Low Refrigerant Refrigerant doesn't get "used up"—if levels are low, there's a leak. This requires professional diagnosis and repair.
5. Failing Compressor The compressor is the heart of your AC system. When it starts failing, cooling capacity drops significantly.
6. Thermostat Issues Sometimes the problem is simpler than you think. Check that your thermostat is set correctly and the batteries aren't dead.
7. Undersized System If your AC has always struggled on hot days, it may be too small for your home. This is especially common in homes where additions were built without upgrading the HVAC.
8. Ductwork Problems Leaky or disconnected ducts can send cooled air into your attic or crawlspace instead of your living areas.
When to Call a Professional
While you can check the filter and thermostat yourself, most other issues require professional diagnosis. If cleaning the filter and condenser coil doesn't solve the problem, it's time to schedule a service call.