After leaf fall, clear the outdoor coil so the unit can breathe. Lift leaves off by hand or with a soft brush. Do not slide a knife, a stick or a pressure washer along the fins. Bent fins block air as surely as the leaves did, and a hose aimed at the electrics is a shock and a fault. If the casing was also damaged, treat it as a storm: isolator off, then an engineer. Leaves alone, on an intact unit, are housekeeping you can do with the power isolated if you want to be cautious.
Leaves on the coil face and in the base tray
They mat across the coil face, pack the gap behind a wall bracket, and fill the base tray so defrost and rainwater sit there. The fan then works against a blocked heat exchanger. Cooling and heating both suffer. The remote still says whatever you set. 16C will not push air through a leaf blanket.
Look from the garden, not by leaning over a spinning fan. Switch the unit off at the remote and wait. If you are going to put fingers near the coil, use the isolator. A fan that starts on a timer is a nasty surprise. Keep shrubs off the discharge for the rest of winter.
Brush, clearances and a coil you do not knife
Gloves, a soft brush, and a vacuum on a low setting held just off the fins are enough for dry leaves. Wet leaves come away in clumps. If a fin bends, stop. Straightening fins is a light comb used by someone who has done it, not a kitchen knife. A knife slips and punctures a tube, and then the job is refrigerant loss and an F-gas repair. Do not hose the electrical panel, the isolator or the cable gland. A gentle rinse of an intact coil face, kept out of the electrics, is as far as a householder should go, and many people should stop at the brush. If you would not wash a socket, do not wash this box. If you have punctured a pipe, stop and isolate. Oily residue on the coil is a leak call, not a leaf clean. Bent fins, or a fan that struck debris, need a service rather than a deeper scrape.
A gap between the unit and the fence, and a shrub that is not growing into the fan, matter more than a heroic clean. Manufacturer clearances are the minimum. In England the Planning Portal still governs where a new unit may sit. Moving it off a leaf trap can be a small relocation, and it is still F-gas work if the pipes are opened. Book this look before the first cold week if you heat with the unit. A blocked coil in heating mode ices up faster and defrosts poorly. The end-of-season service can include this. Leaf fall does not wait for that appointment if the face is already blind.
Frequently asked questions
Can I scrape leaves out of the fins with a knife?
No. You will bend fins or puncture a tube. Lift the leaves and brush lightly. A punctured tube needs an F-gas engineer, not a deeper scrape.
Should I hose the outdoor unit every autumn?
Do not hose the electrics. Dry leaves usually need a hand and a soft brush. If a rinse is used, keep it off the controls and the isolator.
The unit is louder since the leaves arrived. Why?
The fan is pushing against a blocked coil. Clear the face with the fan stopped. If the noise remains on a clean coil, ask for a service rather than turning the setpoint down.
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How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.