Why is my AC running but not cooling?
Short answer: usually one of four things. Air can't get through (a dirty filter or a blocked outdoor coil), the outdoor unit isn't running (a tripped breaker or a failed part such as the capacitor), a clogged drain line has tripped a safety switch, or there's a refrigerant problem. You can check the filter and the breakers yourself. Past that, it's a job for a tech.
See it: the outdoor unit
Tap Call for cooling, then Capacitor fails. Watch the fan.
The fan stopped, but the thermostat is still calling? A tech checks the capacitor first. Don't open the unit: a capacitor can hold a charge even with the power off.
Book a checkIllustration of a generic outdoor unit, simplified. Figure made with Colorfigures.
What can I check myself?
- The air filter. If it's gray and clogged, put in a clean one of the same size. A blocked filter can starve the system of air.
- The breakers. The AC usually has its own breakers in the panel, one for the indoor unit and one for the outdoor unit. If one has tripped (the handle sits in the middle), push it to OFF, then ON, once. If it trips again, leave it off and call a tech.
That's the safe list. Leave the panels on the units closed.
How do I tell if the outdoor unit is running?
Go outside and look at the fan on top. If air is blowing inside but that fan isn't turning, the outdoor unit isn't doing its part, so the air inside never gets cold. A tripped breaker, a failed capacitor or a stuck contactor are common reasons. The figure above shows the capacitor case.
What does a tech check first?
That the thermostat's call reaches the outdoor unit, that the contactor pulls in, and that the capacitor, the fan motor and the compressor are doing their jobs. Then the coils, the drain line and the refrigerant.
Could it be ice or the drain?
Ice on the copper line outside or on the indoor coil means something is wrong with airflow or refrigerant: turn the cooling off and call. A clogged drain line can trip a float switch that shuts the cooling off so water doesn't overflow; a tech clears the line.
When should I call right away?
- A breaker trips again after one reset.
- A burning smell, or buzzing from the outdoor unit with the fan not turning.
- Ice, or water where it shouldn't be.