Everyone agrees that an air conditioner will usually fail when you need it the most, like on one of the hottest days of the year. One afternoon right after coming back home from work, I regrettably found that my air conditioning wasn’t cooling anymore.

Dripping sweat, I frantically called management to send an HVAC professional and schedule a service visit. The HVAC pro informed me that the capacitor on the outdoor unit (the essential piece that gives the motor a jolt of power) had blown due to a buildup of dust and debris. What could have prevented this, he said, was so simple I almost cried. To prevent damage to the crucial parts of the outdoor unit, all you need to do is rinse it with a hose twice a year.

How to Clean an Outdoor Air Conditioning Unit

1. Turn Off the Power to the Air Conditioning Unit

You can safely turn off the power at a disconnect switch near the unit itself or at the circuit breaker in your home's breaker box. Look for a metal box mounted to a house wall near the A/C unit; there will be an electrical cable running from the box to the unit. The disconnect switch is inside the box. Depending on the type of switch you have, you may turn off the power by simply flipping it from on to off. If the switch has a pull-out head, pull out the plastic head from the socket and then flip it upside down and plug it back in (the word "off" will be visible when the head is properly in place).

If there is no disconnect switch near the unit, find the air conditioner circuit breaker inside your breaker box and flip the breaker switch to the off position. This will be a big (double-pole) breaker with a long handle.

2. Open the Top of the Unit

Remove the screws or bolts securing the top panel of the A/C unit. Lift the top and carefully set it aside. It may have fan wiring connecting it to the unit interior; if so, position the top assembly so as not to stress the wiring.

3. Clean the Unit's Interior

Remove leaves and other debris from inside the unit, being careful not to touch any wiring or other electrical components. You can also clean the area with a shop vac and hose extension.

4. Spray the Coil

Screw a nozzle sprayer onto a garden hose and put it on a medium-pressure setting; excessive water pressure can damage the thin metal fins of the coil — the radiator-like structure surrounding the unit interior. Spray the fins with water from the inside out, working from the top down to remove dust and debris. If desired, you can apply a coil cleaning product before rinsing per the product instructions.

TIP

The fins are made of very thin aluminum that bends easily, and they don't work as well when they're bent. You can straighten bent fins with a fin comb, but if they're badly damaged, you should call a pro.

5. Clean the Outside

Clean the outside of the unit with a light spray of water. Reposition the unit's top panel and secure it with its screws or bolts. Let the unit air dry.

6. Restore Power to the A/C Unit

Restore power to the unit by turning on the disconnect switch or flipping the pull-out head and reinserting it in the on position as applicable. Be sure to close and secure the door of the switch box. If you used the circuit breaker to cut power, flip the breaker back to the on position and close the breaker box door.