AC not cooling? Check these first
It's 95 degrees, the AC is running, and the air coming out feels like a sigh. Before you pay for an emergency service call, run through these checks. A surprising number of "broken" air conditioners are really a clogged filter, a thermostat setting, or an outdoor unit choked with dust.
What's actually going on
Central air works by pulling heat out of your house and dumping it outside. The indoor part cools the air, and the outdoor unit, called the condenser, releases the heat through a big grid of metal fins while a fan blows across them. If air can't move through the filter inside, or through the fins outside, the whole system struggles. That's why the first fixes are all about airflow.
One warning sign to know: if you see ice on the copper lines or the indoor unit, turn the cooling off and let it thaw. Running a frozen system can damage the compressor, the most expensive part.
Why it happens
The single most common cause. Without airflow, the indoor coil can even freeze over.
Fan set to ON instead of AUTO blows room-temperature air between cooling cycles, which feels like the AC isn't working.
Dust, grass clippings and cottonwood fluff block the fins, so the unit can't get rid of heat.
A bad capacitor, a stopped fan, or a refrigerant leak needs a licensed technician.
Let's fix it
- Check the thermostatSet it to COOL, fan on AUTO, and a temperature at least 3 degrees below the room. Replace the batteries if the screen is dim or blank. It sounds obvious, but it's the most common fix.
- Replace the air filterA clogged filter starves the system of air and can freeze the indoor coil. If yours is gray, swap it now.
- Check the breakers and the outdoor switchLook for a tripped breaker labeled AC or condenser, and make sure the disconnect box on the wall by the outdoor unit is on.
- Clean the outdoor unitTurn the power off at the disconnect. Clear leaves and weeds 2 feet back, then gently hose the fins from the outside in. Never use a pressure washer, which flattens the fins.
- Give it time and check the airTurn the power back on, wait 5 minutes, and run it for 30 minutes. Air from the vents should feel about 15 to 20 degrees cooler than room air.
Still not fixed?
If the outdoor unit hums but its fan isn't spinning, turn the power off right away. That's usually a failed capacitor, a quick repair for a technician, but running it that way can damage the compressor.
If the indoor unit runs but the outdoor unit is silent, check the outdoor disconnect and breaker again, and look at the thermostat wiring for anything chewed or loose.
What a pro charges: A typical AC service call runs $100–$300. A capacitor replacement usually costs $150–$400; refrigerant leak repairs can run $300–$1,500.
Common questions
Why is my AC running but not cooling?
The most common causes are a dirty filter, a thermostat set to fan-only, a tripped breaker on the outdoor unit, or dirty condenser fins. Check those before calling for service.
Why is there ice on my AC lines?
Usually restricted airflow from a dirty filter, or low refrigerant. Turn cooling off, run the fan to thaw it, replace the filter, and call a technician if it refreezes.
How cold should the air from my vents be?
About 15 to 20 degrees cooler than the air in the room.