Few things are more frustrating than an air conditioner that hums along all afternoon while the house gets hotter. If your AC is not blowing cold air, one of these seven problems is almost always the cause.
1. Low refrigerant from a leak
Air conditioners do not "use up" refrigerant. If the charge is low, there is a leak. Symptoms are warm air, a hissing sound and sometimes ice on the copper line. A technician finds the leak, repairs it, then recharges the system. Topping off without a repair just wastes money. See our AC repair pages for your city.
2. Frozen evaporator coil
Restricted airflow from a dirty filter, dirty coil or weak blower makes the indoor coil freeze into a block of ice. Air cannot pass through ice, so the vents blow warm. Turn the system off, set the fan to on, and let it thaw before calling for frozen coil repair.
3. Failed run capacitor
The capacitor gives the compressor and fan motor the jolt they need to start. When it swells or fails, the outdoor unit hums but nothing spins. It is one of the most common and least expensive air conditioning repairs.
4. Dirty condenser coil
The outdoor coil rejects heat from your home. Packed with dust, cottonwood or grass clippings, it cannot do that job, pressures climb and cooling drops. Annual AC tune-ups include coil cleaning for exactly this reason.
5. Tripped float switch
High-efficiency systems have a safety switch in the condensate drain. When the drain clogs, the switch shuts the system down to prevent a ceiling leak. Clearing the drain restores cooling.
6. Failed contactor or fan motor
A pitted contactor or seized condenser fan motor stops the outdoor unit from running. The indoor blower keeps going, so you feel air, just not cold air.
7. Compressor failure
The most serious cause. A compressor that trips the breaker, runs hot or will not start needs a careful diagnosis. Compressor repair or replacement is sometimes the right call, sometimes a new condenser is. We give you both numbers.
When to call
If the filter is clean and the breaker is on but the air is still warm, it is time for a professional. Emergency AC repair is available 24/7 across California at (855) 459-5498.