Cleaning an air conditioner and running it efficiently

Why cleaning cuts both odour and bills

An air conditioner draws in room air, passes it over a cold heat exchanger and blows it back out. Along the way, moisture in the air condenses on the heat exchanger and dust gets caught in the filter. A clogged filter weakens the airflow, so the unit has to run longer to reach the same temperature, and leftover moisture and dust make an ideal home for mold, which causes that sour smell. Cleaning therefore takes care of hygiene and your electricity bill at the same time.

Filter cleaning comes first

Many manufacturers suggest checking the filter about every two weeks during the cooling season, but follow your manual for the exact interval and how to remove it. Always unplug the unit or switch off the breaker before you start. If there is a lot of dust, vacuum the surface first, then wash the filter gently with a soft brush in lukewarm water with a mild detergent. Let it dry completely in the shade before putting it back.

• Unplug the unit
• Vacuum the dust off first
• Lukewarm water, mild detergent, soft brush
• Dry fully in the shade before refitting

Mistakes that ruin the filter

Blasting the filter with a hot hair dryer or leaving it in strong sun for hours to speed things up can warp the frame or damage the mesh. Refitting a filter that is still damp brings the moisture straight back and with it the smell. Scrubbing with a stiff brush or scourer stretches the fine mesh so it no longer catches dust properly. Running the air conditioner without a filter is also a bad idea, as dust builds up inside right away.

Dry the inside before switching off

The easiest way to prevent odour is to dry the inside after cooling. Run the fan mode for a while before switching off, or turn on the auto-dry function if your unit has one. Switching off straight after cooling leaves condensation sitting on the heat exchanger, where mold grows easily. In humid periods such as the rainy season this habit makes a big difference. When summer ends and the unit will sit unused, drying it thoroughly on fan mode first means much less smell when you start it next year.

• Run the fan for a while before switching off
• Turn on auto-dry if available
• Dry thoroughly before the off-season

How much of the inside to clean yourself

You can wipe the filter, the casing and the louvres where air comes out, but the heat exchanger and the depths of the blower fan are complex and close to electrical parts, so do not force your way in. If you use a cleaning spray, first check the manual to see whether it is allowed, never spray electrical parts, and open a window for ventilation. If the smell persists after cleaning the filter, or you can see black marks inside the louvres, it is safer to have a professional take the unit apart and clean it.

The outdoor unit decides efficiency

An air conditioner moves heat from inside to the outdoor unit, so if the outdoor unit cannot shed that heat, efficiency drops sharply. Stacking things in front of or behind it, or running it with a cover on, traps the hot air. If you want to shade it from the sun, a canopy above it that does not block airflow is enough. If the outdoor unit sits inside an enclosed balcony, always open the window or vent while it is running.

• Keep the area around it clear
• Remove any cover while in use
• Shade it without blocking airflow
• Open windows or vents if it is on a balcony

Running it with less electricity

Setting the temperature very low simply makes the unit run harder for longer. A summer indoor temperature of around 26 degrees is commonly recommended, and using a fan or circulator to move the cool air lowers the temperature you feel, so you stay comfortable with a slightly higher setting. During the day, block sunlight with curtains or blinds. With the inverter models common today, leaving it on at a moderate temperature is often better than switching on and off repeatedly, but this varies by model, so check the manual.

• Set it at around 26 degrees and adjust
• Use a fan or circulator alongside
• Block sunlight with curtains
• Avoid frequent on and off with inverter models

Checklist at the change of season

When you first turn it on before summer, clean the filter, then run the cooling briefly to confirm that cold air comes out, that water drains properly through the hose, and that there are no strange sounds or smells. If the air is lukewarm or water drips from the indoor unit, there may be a refrigerant or drainage problem, so have a professional inspect it. Do not touch the refrigerant pipes yourself, as that is dangerous. If a cable feels hot or you smell burning, switch off the power at once and stop using it.