Caring for your air conditioner yourself
DIY maintenance of small air conditioners
Clean the filters, keep the outdoor unit clear, keep an eye on the condensate: how to care for your split wall unit or portable air conditioner safely – and how to recognise when a specialist is needed.
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What you can do yourself – and what not
Small air conditioners such as split wall units and portable air conditioners need little care. As an owner, you can do a few simple tasks yourself. Anything involving the refrigerant circuit, the electrics or opening the unit belongs in the hands of specialists.
The operating instructions of your unit always take precedence. The information on this page is general and does not replace the manufacturer's instructions.
As of October 2026
Do it yourself
Six tasks for owners
Before any care, switch off the unit and disconnect it from the power supply.
Clean the filters
During the cooling or heating season, check and clean the air filters every 2–4 weeks, more often with a lot of dust, pets or continuous operation. Remove the filters as described in the instructions, vacuum them or rinse them with lukewarm water, let them dry completely and put them back in.
Wipe the indoor unit
Wipe the outside of the casing and air louvres with a soft, slightly damp cloth. Do not use harsh cleaners or solvents, and do not spray water into the unit.
Keep the outdoor unit clear
Keep leaves, snow, plants and objects away from the outdoor unit so that air can flow in and out freely. Do not bend the fine fins and do not place anything on the unit.
Watch the condensate drain
Check that the condensate drains normally: on a split unit through the hose to the outside or into a drain, on a portable unit into the tank or through the drain hose. Empty the tank of the portable unit regularly.
Let it dry after cooling
After cooling, let the indoor unit run in fan mode for a while so that it dries inside. This prevents odours. Depending on the model, there is a dedicated drying function for this – see the instructions.
Remote control batteries
If the unit no longer responds reliably, first replace the batteries in the remote control. Old batteries belong at a collection point.
Unit types
Split wall unit and portable air conditioner
The care is similar, the details differ.
Split wall unit
- The air filters are usually located behind the front flap of the indoor unit.
- The condensate drains through a hose. If water drips from the indoor unit, that is a warning sign.
- The outdoor unit stands outdoors: keep it clear and do not cover it while the system is in operation.
Portable air conditioner
- Depending on the model, the filters are located at the back or on the side.
- Empty the condensate tank or check the drain hose.
- Route the exhaust hose as short as possible and without kinks, and check the window seal.
- Before storing it for the winter, drain the unit completely and store it dry.
What you should not do yourself
- No refrigerant work: Only specialists with a licence for handling refrigerants may top up refrigerant, open pipes or loosen connections.
- No high-pressure cleaner: The hard water jet bends the fine fins and can force water into the electrics and bearings – on both the indoor and the outdoor unit.
- Power off first: Before any cleaning, switch off the unit and disconnect it from the power supply – pull the plug or, for permanently connected units, switch off the fuse or the isolating switch.
- Do not open the unit: The specialist company cleans and checks the heat exchanger, fan, condensate tray and electronics inside.
- No sprays into the unit: Only use cleaning or disinfectant sprays if the manufacturer expressly approves them.
Warning signs
Then call a specialist company
If you notice these signs, switch off the unit and have it checked.
Unpleasant smell
A musty or foul smell when switching on indicates dirt inside, for example on the heat exchanger, the fan or in the condensate tray.
Water drips
If water drips from the indoor unit, the condensate drain is often blocked or the unit is no longer level.
Ice on the unit
Ice on the pipes or on the heat exchanger can indicate very dirty filters, too little airflow or a fault in the refrigerant circuit.
Weak performance
If the unit cools or heats noticeably worse than before despite clean filters, the refrigerant circuit should be checked.
Unusual noises
Rattling, grinding, whistling or loud humming – inside or outside – should be checked before consequential damage occurs.
Error code
If the display or remote control shows an error code or an indicator flashes, note the code and switch off the unit. With the code, the fault can often be narrowed down quickly.
Report the fault to us by phone or WhatsApp – ideally with a photo of the rating plate and the error code.
Regular maintenance by a specialist company
Your own care does not replace maintenance. We recommend annual maintenance for air conditioning systems; the manufacturer's specifications are decisive. We clean the heat exchanger, condensate tray and drain, disinfect the indoor unit, measure pressures and temperatures, check the electrics and tightness and record everything in a service report.
Price on request: you will receive a quote tailored to the number and type of units. For regular maintenance we offer maintenance contracts – for all brands.
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Services
Planning, building permits, installation, maintenance and repairs – for all brands
FAQ
Questions about caring for air conditioners
How often do I have to clean the filter?
Every 2–4 weeks during the cooling or heating season, more often with a lot of dust, pets or continuous operation. The operating instructions of your unit are decisive.
May I top up the refrigerant myself?
No. Only specialists with a licence for handling refrigerants may work on the refrigerant circuit. If refrigerant is missing, the circuit is leaking – the specialist must find and repair the leak.
What should I do if water drips from the indoor unit?
Switch off the unit, catch the water and call a specialist. A common cause is a blocked condensate drain.
Does your own care replace maintenance?
No. Cleaning the inside, measurements and leak testing are part of maintenance by a specialist company. We recommend annual maintenance.
Let’s discuss your project
Book maintenance or report a fault: call us or write to us – for all brands.