AC Not Cooling?
Check These First.

Work through these in order. None of them needs tools, and none involves opening a panel on the equipment. If you reach the end and the house still isn't cooling, you've also gathered useful information for the technician.

1. Is the thermostat actually asking for cooling?

Confirm the mode is set to Cool, not Heat, Auto-changeover or Off, and that the set temperature is several degrees below the room temperature. Set the fan to Auto. If the display is blank, replace the batteries. A thermostat that's lost power is a surprisingly common cause of a system that seems dead.

2. Is the air filter clogged?

Pull the filter and hold it up to a light. If you can't see light through it, replace it. A clogged filter starves the system of airflow, which reduces cooling and can cause the evaporator coil to freeze. Most filters need changing every one to three months, more often with pets or construction dust nearby.

3. Did a breaker trip, or is the outdoor switch off?

Check the breaker panel for the air conditioner and for the furnace or air handler, since the indoor unit has its own circuit. Look for a tripped breaker sitting in the middle position. Reset it once. If it trips again right away, stop. Repeated tripping means something in the system is failing, and resetting it again can damage it. Also check the disconnect box near the outdoor unit to make sure the handle or pull-out block is in place.

4. Is the outdoor unit running, and is it clear?

Stand near the outdoor condenser with the system calling for cooling. You should hear the fan and compressor running and feel warm air blowing out of the top. Make sure leaves, cottonwood fluff, grass clippings or a fence aren't blocking the sides, and keep about two feet of clearance. If the fan runs but the unit hums and nothing else happens, shut the system off at the thermostat and call us. Don't try to start it by hand.

5. Look for ice

Ice on the larger copper line near the outdoor unit or on the indoor coil means the system is freezing up, usually from poor airflow or low refrigerant. Turn the cooling off and set the fan to On so the ice melts. Give it several hours. Don't chip ice, and don't run the compressor while it's frozen. If it freezes again after a new filter, you've got a problem a technician needs to find.

6. Check for a drain backup

Modern systems have a safety switch that shuts cooling off if the condensate drain backs up. If you see water around the indoor unit or in the drain pan, or a pan float switch has tripped, the system may shut itself down on purpose. Clearing a clogged drain line is a fix a technician can do quickly, and it's worth doing to avoid ceiling or floor water damage.

7. Is it cool but not cool enough?

If the system runs all day and gets the house within five or six degrees of the setpoint on a hot afternoon, it may simply be working near its capacity during a heat wave. Closed supply vents, a west-facing room with big windows, leaky ducts in a hot attic and an undersized system for an addition all create the same complaint. These are worth a visit but aren't emergencies.

Stop and call right away if

You smell something burning or hear grinding or loud banging from the equipment. A breaker trips more than once. The outdoor unit is hot but the air from the vents is warm. There's heavy ice or water pouring from the indoor unit. Turn the system off at the thermostat and book service.

What the technician will do

We start with the same simple checks, then measure airflow, electrical readings and refrigerant pressures, inspect the coils and drain, and tell you what we found and what it costs before we fix anything. Our dispatch fee for HVAC is $49, applied toward any approved repair. If the system is old and the fix is expensive, we'll show you both the repair and the replacement numbers instead of pushing a new unit. See our AC repair page for more, or read our guide on how long furnaces and air conditioners last in Utah to decide whether repairing makes sense.

Related Homeowner Answers

• Why does my breaker keep tripping? An AC that keeps tripping its breaker needs a technician, not repeated resets.
• How long do ACs last in Utah, and when is it time to replace?
• AC repair and HVAC maintenance