How to Stop Birds Perching on an Outdoor Air Conditioning Unit

To stop birds perching on an outdoor air conditioning unit, fit humane deterrent spikes along the flat top edges and any ledge the birds use, fixed with waterproof adhesive pads rather than screws so you never drill into the casing. Keep every spike clear of the fan outlet and the vents, and check the unit's manual for minimum clearances. Where the top is the fan outlet, deter birds from the bracket, wall ledge or fence beside it instead.

Why do birds keep landing on my AC unit?

An outdoor condenser gives birds a flat, raised, sheltered perch, usually with a good view and a wall behind it. Pigeons in particular like a dry ledge to sit on, and a unit tucked beside a wall or under an overhang is an easy place to loaf. Droppings build up on the casing and on whatever is underneath, such as paving, a window sill or your washing.

The unit is also not a surface you want to treat like a shed roof. The fins and fan need airflow, and the casing contains electrics and refrigerant pipework. That is why the method needs more care than fixing spikes to a fence.

What should I check before fitting anything to the unit?

Work through this list first:

1. Find the air discharge. Many units blow air out through a round grille on top. Others discharge from the front or side, leaving a flat lid. Never put spikes where they would sit over or close to a discharge grille.
2. Read the clearance guidance in the installation manual. It will state how much free space is needed around the unit. Spikes should not eat into that space.
3. Check for nests. If a bird is nesting on or in the unit, leave it alone until the nest is no longer in use. In the UK it is an offence to damage or destroy an active nest. Our guide to whether bird spikes are legal in the UK explains the rules.
4. Check who owns it. If the unit is installed by a landlord, or is under warranty or a maintenance contract, ask before attaching anything to it.

Is it safe to drill into an AC unit to fit spikes?

No. Do not drill or screw into the casing. Behind the panels are the compressor, wiring and coil, and a stray screw can cause damage that is expensive to fix. It also tends to void any warranty.

That makes this a job for adhesive. ThornGuard packs include screws and cable ties, and we also sell separate waterproof adhesive pads for surfaces you can't drill, including AC units, render and uPVC. Our guide to fixing bird spikes without drilling covers the adhesive method in more detail.

How do I fit spikes to an AC unit step by step?

1. Switch the unit off at its isolator before you start. You will be working close to the fan and vents.
2. Clean the fixing surface. Wipe off droppings, dust and any grease, then dry it fully. Adhesive will not hold on a dirty or damp surface. When cleaning droppings, wear gloves and a dust mask, and dampen them first instead of dry-brushing them. Do not hose or pressure-wash the unit itself.
3. Measure the edges the birds use. This is usually the front lip and the side edges of the top panel. Cut the strip to length. You can cut across the sections, or split it lengthways to cover more ground on a narrow edge. Our guide on how to cut bird spikes to size shows how.
4. Dry-fit the strip first. Lay it in place and check that no spike overhangs a vent or grille, and that nothing can catch a hand when you open the service panel.
5. Apply the adhesive pads to the underside of the strip and press it firmly onto the clean surface. Follow the instructions on the pad pack for pressing time and for how long to leave it before the unit runs again.
6. Check the fit after the first few weeks of weather and press down any lifting corners.

The strip folds four ways along its length, so it can wrap around the corner of a panel and cover an edge on more than one side. That helps on a unit where birds step from the top onto a side ledge.

Which spikes work best on an AC unit?

Choose spikes that cope with both birds and animals. ThornGuard strips have an irregular three-height design of 12mm, 22mm and 36mm. The staggered heights leave no flat landing spot for a pigeon, and they also stop a squirrel, fox or cat using the unit as a stepping stone onto a wall or lean-to roof. Flat single-height spikes tend to leave gaps that birds can balance in.

The material matters here too, because the unit sits outdoors all year. ThornGuard spikes are made from UV-stabilised virgin polypropylene, so they resist the brittleness that makes cheap spikes snap after a winter. If you have had that problem, see why bird spikes snap or go brittle.

Spikes deter birds from landing. They do not harm them, and no deterrent works on every bird in every situation, so it is worth covering all the perches nearby, not just the unit.

What if the top of the unit is the fan outlet?

Then leave the top clear and take away the perches around it. Options, in the order we would try them:

• Fit spikes to the nearest approach points: the wall bracket, a ledge above the unit, the fence top or the window sill next to it. Birds often land there first before dropping onto the unit.
• Use a sloped cover. A raised, angled hood, built or bought to suit your model, makes the top too steep to sit on. It must leave the discharge path and clearances completely open, so check the manual or ask your installer.
• Remove the draw. Pigeons return to spots where they have been fed. If someone nearby is feeding them, or there is spilled seed under a feeder, the birds will keep coming back.

If you are also dealing with birds on the nearby roof or ledge, our guides on keeping pigeons off your roof and protecting window ledges from pigeons cover those perches. You can see the strips and packs on the ThornGuard product page, and the fitting guide has measuring and fixing tips.

Common questions

Will spikes stop my air conditioner working properly?

Not if they are fitted correctly. Keep them off the fan grille, vents and any clearance zone in the manual, and attach them only to flat edges that don't affect airflow. If you are unsure, ask the installer where spikes can safely go.

Can I use cable ties instead of adhesive on an AC unit?

Only if there is a solid bracket, rail or pipe clip that is not part of the unit's working parts, and you must never tie to refrigerant pipes. On a smooth casing, adhesive pads are the safer choice because you don't need to drill or pull anything tight against the unit.

What should I do if birds are already nesting on or in the unit?

Leave them alone until the nest is finished with, because disturbing an active nest is illegal in the UK. Fit the spikes afterwards, once the nest is empty and the unit has been cleaned, to stop them coming back next season.