Why Your AC Isn't Cooling (8 Causes)

Start with the free checks

1. Thermostat set correctly and in cool mode, not fan-only. 2. Air filter clogged — the single most common cause. 3. Outdoor unit blocked or recirculating its own hot air against a wall or fence. 4. Breaker tripped for the outdoor unit only, which leaves the indoor fan running and feels like a working system.

Then the mechanical causes

5. Frozen evaporator coil from restricted airflow or low charge. 6. Dirty condenser coil — especially on salt-air properties. 7. Failed capacitor keeping the compressor from starting. 8. Actual refrigerant leak, which is diagnosed last, not first.

Why order matters

A technician who adds refrigerant before checking airflow will overcharge the system, and an overcharged system cools worse than an undercharged one. Airflow first, electrical second, charge third.

Frequently Asked Questions

Why does my AC freeze up in Hawaii?

Almost always restricted airflow — a clogged filter, dirty coil, or blocked return — rather than low refrigerant, which is the common internet answer.

AC runs but air isn't cold — biggest cause?

An outdoor unit that is not actually running. Check the breaker and the capacitor; the indoor fan will still blow warm air and make it look like the system is on.

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