Common Air Conditioner Problems and Practical Solutions (HVAC Guide)

Air conditioners often show early warning signs before a major breakdown. Knowing the most common HVAC and air conditioning problems helps you restore comfort faster and avoid costly repairs. 1) The AC is running but not cooling. Start with the thermostat mode (Cool) and setpoint. Check the air filter: a clogged filter restricts airflow and reduces cooling. Inspect the outdoor condenser for blocked fins, leaves, or dust; gently clean to improve heat transfer. If the issue persists, low refrigerant or a failing compressor may be involved—this requires a licensed technician. 2) Weak airflow from vents. Dirty filters, blocked supply vents, or a struggling blower motor are typical causes. Make sure vents are open, replace the filter, and confirm the fan setting is correct. If airflow is still low, the ductwork could be leaking or the evaporator coil may be dirty. 3) Ice on the indoor unit. A frozen evaporator coil usually means poor airflow (dirty filter, blocked coil) or low refrigerant. Turn the system off to thaw, replace the filter, and schedule service if icing returns. 4) Water leaks around the indoor unit. Condensate drains can clog with algae or dust. Clear the drain line and ensure the drain pan is intact and level. Persistent leaking may indicate improper installation or coil freezing. 5) Strange noises or odors. Rattling can mean loose panels; buzzing may indicate electrical issues; squealing can point to belt or motor problems. Musty smells often come from moisture and mold—cleaning the drain and coil can help. Regular maintenance—filter changes, coil cleaning, and seasonal inspections—improves efficiency, indoor air quality, and system lifespan.