Is your air conditioner no longer cooling as well as it used to, or does it smell strange when you switch it on? In most cases, the cause lies in the filters: they trap dust, mites and pollen from the air and, when they become clogged, the unit has to work harder and the air comes out in worse condition. Cleaning them is a simple task that you can do yourself in a few minutes.
In this guide we explain how to clean air conditioner filters step by step, how often to do it and what to do if the air still smells bad even with clean filters.
The impact of poor maintenance on air conditioning
The build-up of dust, mites and pollen in the internal components of a residential air-conditioning system directly affects its thermodynamic efficiency. When particles obstruct the airflow, the heat transfer rate drops drastically. This forces the compressor to work longer cycles, increasing mechanical wear and electricity consumption.
Beyond the purely economic aspect, indoor air quality gradually deteriorates. Clogged filters and moisture retained in the condensate tray become the ideal breeding ground for colonies of fungi and bacteria, which are directly responsible for bad odors and for triggering respiratory allergies.
What you need to clean the filters
Before starting the technical process, it is essential to gather the right items to ensure a deep clean without damaging the polymer components or the delicate aluminum fins of the evaporator.
- Lukewarm water and neutral soap: The ideal combination for removing surface dirt from the plastic mesh.
- Clean microfiber cloth: Essential for trapping particles without shedding fibers or generating static electricity.
- Vacuum cleaner with a soft brush nozzle: Ideal for quickly removing coarse dust.
- Soft-bristle brush: A key tool for removing residue lodged between the grilles.
- Professional chemical treatment: To completely eliminate bacteria and ingrained dirt in the circuits, an air-conditioning cleaning spray such as AIRNET SPRAY becomes indispensable: a specialized spray that dissolves grease without damaging the materials.
How to clean air conditioner filters step by step
Follow these steps on a wall-mounted split unit. In cassette or ducted units, the filters are in the ceiling grille or in the return: consult the manufacturer’s manual. If you need specific products, you will find them in our air conditioning cleaning category.
Electrical safety management
Personal safety is the top priority in any domestic maintenance task. Before removing any casing or handling components, you must disconnect the unit from the mains power. It is not enough to switch it off with the remote control; unplug the unit from the socket or flip the corresponding circuit breaker in your home’s electrical panel. This completely eliminates the risk of short circuits or accidental shocks.
Remove and wash the split unit filters
The filters are the system’s first line of defense. Cleaning them regularly ensures a constant, clean airflow.
- Opening the cover: Hold the sides of the split’s front casing firmly and gently lift it upward until it locks into its automatic open position.
- Removing the mesh filters: Locate the retaining tabs at the bottom of the filters. Press up slightly and slide the pieces down gently to take them out of their guides.
- Dust removal: If you see a thick layer of dirt, use a vacuum cleaner at low power to remove most of the dust before wetting the part.
- Systematic washing: Place the filters under the tap or in the shower using lukewarm water. Apply neutral soap and rub gently by hand. Avoid boiling water and stiff brushes entirely, as they could irreversibly deform the fine plastic mesh.
- Drying process: Let the parts air-dry in a shaded place. Never expose the filters to direct sunlight or use hair dryers. Do not reinstall the filters if they are still damp, as this would immediately encourage mold growth.
Take the opportunity to check the coil and the tray
Behind the filters lies the thermal heart of the indoor unit, an area prone to the accumulation of microscopic sediment where water and ordinary soap are not enough.
Use the soft-bristled brush to clean the aluminium fins of the evaporator, with vertical movements from top to bottom. If the coil is dirty, soap and water are not enough: spray AIRNET® SPRAY with the unit running and the dirt will come out through the drain. To disinfect it and eliminate bad odours, then apply AIRPUR® SPRAY. You will find the complete process in our guide to cleaning and disinfecting a split air conditioner.
Next, inspect the drain pan located at the bottom of the evaporator block. This part collects the water from ambient condensation. Check that the pipe is free of blockages and standing water that could cause overflows and leaks on the wall. Clean the surface of the pan with the dampened microfiber cloth.
Outdoor unit maintenance
The compressor and condenser located outside the home are exposed to the weather, collecting leaves, pollution and organic debris.
Use a vacuum cleaner or a dry brush to clear the external ventilation grilles. If the build-up of dirt is severe, you can use a low-pressure hose to wash the outdoor heat exchanger, always directing the water from the inside out and without wetting the electrical junction boxes. For grease on the outdoor coil there are specific cleaners, such as AIR SERNET RTU.
Verification and dynamic drying protocol
Once all the parts are completely dry, reassemble the filters and close the front cover of the split. Reconnect the unit to the mains and switch it on, selecting only fan mode for a period of 10 to 15 minutes. This produces a constant airflow that helps distribute the sanitizing agents and evaporates any minimal traces of moisture left trapped in the internal ducts.
Analysis of the benefits of preventive maintenance
| Evaluation Factor | With Saturated Filters (No Maintenance) | With Clean Filters (Maintenance Up to Date) |
| Energy consumption | Higher electricity consumption due to the extra strain on the compressor. | Efficient operation within nominal design parameters. |
| Air quality (IAQ) | Spread of dust, bacteria, mold spores and bad odors. | Optimal allergen retention and purified airflow. |
| Motor service life | Premature compressor wear caused by thermal overload. | Smooth operation, reducing the rate of mechanical failures. |
| Cooling capacity | Prolonged duty cycles with low temperature transfer. | Fast, uniform air conditioning of rooms. |
Recommended frequency and solutions for bad odors
To ensure maximum operating efficiency, it is advisable to carry out this deep cleaning at least twice a year. The ideal time coincides with the change of seasons: one thorough session just before the start of the summer season and another before switching on heating mode in winter. If people with chronic respiratory problems or severe allergies live in the home, or pets that shed a lot of hair, it is advisable to check the filters once a month during periods of continuous use.
If you notice a musty smell when you switch the unit on, the source is the fungi and bacteria on the coil, not the filters. Clean the coil with AIRNET® SPRAY and then disinfect it with AIRPUR® SPRAY, a bactericide and fungicide that eliminates the cause of the odour. In professional maintenance, AIRNET PRO and AIRPUR PRO perform the same function.
Frequently Asked Questions
Can I use harsh chemicals such as pure bleach to clean the filters?
It is not recommended. Concentrated bleach and other corrosive chemical cleaners can severely degrade the structure of the plastic threads of the filter mesh and permanently oxidize the aluminum fins of the split. It is preferable to use neutral solutions or specific products tested for air-conditioning systems.
What happens if I run the air conditioner completely without the filters in place?
Running the system without filters allows all the dust, hair and dirt suspended in the air to settle directly on the evaporator coil and clog the drain pan. This drastically reduces the transfer of cooling or heat and can cause serious breakdowns from system freeze-up or mechanical blockages within a few days.
Why is my air conditioner dripping water down the interior wall after cleaning?
This usually happens if the drain tray has moved from its original position during cleaning or if the loosened dirt has blocked the opening of the drain pipe. Make sure that the drain channel is completely clear and that the pipe keeps a downward slope towards the outside.