AC Not Cooling? Five Things To Check Before You Call
An air conditioner that runs but does not cool is the single most common call we take between June and September. Roughly one in five of those turns out to be something the homeowner could have sorted in ten minutes. Here is how to check, in the order that finds problems fastest.
1. Look at the filter first
A clogged filter starves the evaporator coil of airflow. The coil gets too cold, condensation freezes on it, and the ice blocks what little airflow was left. From the living room this looks exactly like a broken AC: the unit hums, the fan runs, and the vents blow weak, room-temperature air.
Pull the filter. If you cannot see light through it, replace it. Then switch the system to fan-only for two to three hours to melt any ice off the coil before running cooling again. Running it while frozen risks liquid refrigerant reaching the compressor, which is a far more expensive problem than a filter.
2. Check both breakers
Central air runs on two circuits: one for the indoor air handler or furnace, one for the outdoor condenser. If only the outdoor breaker trips, the indoor fan keeps blowing while nothing is being cooled. Homeowners often check the panel, see the furnace breaker on, and assume power is fine.
Reset a tripped breaker once. If it trips again immediately, stop and call. A breaker that keeps tripping on the condenser usually means a shorted compressor winding, a failed capacitor or damaged wiring, and repeated resets can turn a repair into a replacement.
3. Confirm the thermostat is actually calling for cool
Sounds obvious, and it accounts for a real share of no-cool calls. Check that the mode is on COOL rather than FAN or HEAT, the setpoint is at least three degrees below room temperature, and the fan is on AUTO rather than ON. Fan set to ON runs the blower continuously, so warm air keeps moving through the vents between cooling cycles and the system feels broken when it is not.
If the display is blank, replace the batteries. Many thermostats also have a low-voltage fuse on the furnace control board that blows when a wire shorts.
4. Walk out to the outdoor unit
Three things to look for. Is the fan on top spinning? Is the coil packed with cottonwood fluff, grass clippings or leaves? Is there anything crowding it within about two feet?
A condenser humming with a still fan is almost always a failed run capacitor, a cheap part and a same-visit repair. A coil buried in debris can be rinsed gently with a garden hose from the inside out, power off at the disconnect first. Restricted airflow across that coil raises head pressure, kills capacity and shortens compressor life.
5. Check the condensate drain and float switch
Air conditioning pulls a surprising amount of water out of the air. That water leaves through a drain line that grows algae and clogs. Many systems have a float switch that cuts the whole system off when the pan fills, to stop water reaching your ceiling.
If you find standing water in the drain pan, the switch has probably done its job. Clearing the line and confirming the switch resets is straightforward work.
If all five check out
Then you are into refrigerant, compressor, contactor or control territory, and that needs gauges. Low refrigerant is not something to top up and forget; refrigerant does not get consumed, so low charge means a leak that needs finding and repairing. Book AC repair and we will diagnose it properly rather than swapping parts and hoping.
You can book in any Washington city — Seattle, Spokane, Tacoma, Vancouver or Yakima — from our service areas page. Related reading: repair or replace: how to decide and what a real AC tune-up includes.
Need this fixed rather than explained? Call (888) 380-4427 any hour, or find your city on our service areas page.