Why Won't My Outside AC Unit Turn On?

You turn on the air and notice that it's not getting any cooler inside. A quick glance outside shows the outside AC unit not turning on. What's going on?

Before you call for an air conditioning repair, there are a few things you need to check.

Check the Thermostat

It should be set to cool. Set the temperature to 5 degrees below the inside temperature and see if the outside unit comes on.

Look for a Tripped Breaker

If your AC won't turn on, you can check two places for a circuit breaker or electrical panel. Older homes have a main electrical panel on the outside of the home or a circuit panel on newer homes. Check the electrical panel to see if the breaker is tripped. Reset it if it is. Then see if the outside unit comes on. If the breaker trips again, let a professional handle it.

Change the Air Filter

If you notice that your outside AC unit won't turn on, check your air filter. As your air filter becomes clogged with dust, hair, and other particles, it blocks airflow into your HVAC system. This can cause the equipment to overheat and shut off.

Check the Shut-off Switch

Outside AC units have an electrical switch next to them which allows the power to be cut from the exterior. Make sure the switch is in the on position.

Check the Inside Shut-off Switch

Often, your AC will have a shut-off switch in the attic or even a closet that can shut off the power to your HVAC system. You'll want to make sure that is in the on position. If it is shut off, neither the inside nor the outside units will turn on. The switch will look like a normal light switch, which people can turn off by accident.

Make Sure the Condensate Line Is Clear

The internal AC unit has a pan beneath that catches condensate run-off. That pan usually has a drain line attached to it that allows the water out of the house. If that line gets clogged, it can trip a switch that shuts everything off.

Try the Reset Button

If your unit has a reset button, push it and see if it helps. If it doesn't have one, you can turn off the AC at the thermostat and turn it back on in 5 to 10 minutes.