What to Do If Your AC Stops Working

When the air conditioner quits on a hot day, it is tempting to call for service right away. A few simple checks can sometimes get it running again, and if they don't, you will be able to tell the technician exactly what you already tried.

1. Check the thermostat

Make sure the thermostat is set to Cool, the target temperature is below the current room temperature, and the fan is set to Auto. If the display is blank, replace the batteries. Programmable thermostats can also be stuck on a schedule or a "hold" setting.

2. Look at the breaker and the outdoor disconnect

Central AC systems usually have a breaker in the main panel and a disconnect switch near the outdoor unit. If a breaker has tripped, reset it once. If it trips again, stop there: repeated tripping points to an electrical problem that needs a professional.

3. Replace or clean the air filter

A clogged filter restricts airflow, which can cause weak cooling or even a frozen indoor coil. Hold the filter up to the light; if you can't see through it, replace it with the same size.

4. Check for ice on the lines or coil

If you see ice on the copper refrigerant line or the indoor coil, turn the system to Off and set the fan to On so the ice can melt. Running the system while frozen can damage the compressor. Ice that comes back usually means low refrigerant or an airflow problem, both of which need a technician.

5. Clear around the outdoor unit

Leaves, grass clippings and overgrown plants around the condenser block airflow. Turn the power off at the disconnect and clear debris from around the unit, leaving a couple of feet of open space.

6. Check the condensate drain

Many indoor units have a safety switch that shuts the system down when the condensate drain line or pan is full. If you see standing water in the pan, the line may be clogged.

When to call a pro

• The breaker trips more than once.
• You hear grinding, buzzing or clicking without the system starting.
• Ice keeps forming on the lines or coil.
• You smell burning or notice a refrigerant (chemical) odor.
• The outdoor fan doesn't spin while the system is calling for cooling.

Refrigerant and high-voltage components should only be handled by a qualified HVAC technician. When you request quotes, mention the steps above and what you observed: it helps the pro come prepared.