How to Clean an Outdoor AC Coil

The outdoor coil dumps heat from the house into the yard. Cottonwood, grass, and dust mat it over in late spring around Vancouver, and the system has to run longer to reject the same heat. A gentle rinse is reasonable homeowner maintenance. Everything past that belongs to a technician.

A safe rinse

• Set the thermostat to Off. Pull the outdoor disconnect or switch the breaker off. Confirm the fan is not spinning and is not trying to start.
• Do not remove the electrical panel cover. You do not need to, and the capacitor behind it can hold a charge.
• If the top grille or a side panel is meant to lift off without tools, and you can see through the coil, rinse from the inside toward the outside. Water then pushes dirt out of the fins instead of into them.
• Use a garden hose. A pressure washer folds the fins flat, and folded fins block air as badly as the dirt did.
• Skip household cleaners, bleach, and coil solvents from a shelf unless the product is made for condenser coils and you can keep it out of the electrical side and the lawn. Water is enough for loose cottonwood.

Let the coil dry before you restore power. A bent section of fin can be straightened with a fin comb by someone who does this often. Pliers make it worse.

What this will not fix

The indoor evaporator coil is in the ducted cabinet. Hosing it from a register, or spraying it in place, floods the furnace and the drain. If cooling is weak after the outdoor coil is clean, the filter, the indoor coil, the charge, and the blower are next. A matted outdoor coil is one cause of high head pressure. It is not every cause.

If the unit still cannot keep up, or the fan will not start after you restore power, stop retrying it and book AC repair. A seasonal cleaning visit is AC maintenance, which includes the indoor coil you should not hose.

Common questions