Air conditioner running but not cooling: filter, outdoor unit, refrigerant and when to call service

• Switch off the MCB and unplug the appliance before checking anything.
• Make sure your hands and the floor are dry.
• Never puncture, cut or recharge the refrigerant lines; that work is for a certified technician only.
• Capacitors keep an electric charge after the plug is pulled; this part is not opened at home.

If your AC is hardwired to the MCB with no plug, switch off its dedicated MCB first. If the outdoor unit is mounted high on a wall, do not climb up to it; look at it from a safe spot.

A split air conditioner has two parts that must both work. The indoor unit draws room air through the filter, cools it over the evaporator and blows it back out. The refrigerant carries the heat from the room to the outdoor unit, where a fan helps release it through the condenser. If the filter is clogged, air cannot pass. If the outdoor unit cannot get rid of heat, the cooling weakens even though the indoor unit keeps blowing.

LG Indonesia's help page sums up the most common causes: a weak cooling mode, a set temperature that is too high, or airflow aimed upward. It also lists an outdoor unit in a space without good ventilation, dust built up on the filter, and hot air coming in from outside. The Modena split AC manual adds blocked air inlets or outlets, sunlight coming straight in through a window, and a large heat source in the room. Almost all of these can be checked without opening anything.

If all of that is fine and the AC still only blows room-temperature air, it is time to suspect low refrigerant or a failed outdoor part, and that is a job for a technician.

1. Mode and temperature. LG explains that in auto, AI or dry (dehumidify) mode, the cooling can feel weak. Choose cool mode and set the temperature below the room temperature; the bigger the difference, the colder the air.
2. Cooling test. To be sure, LG suggests running normal cool mode with the temperature set to 18 degrees for more than 30 minutes before you judge it.
3. Louver direction. On wall-mounted units, efficiency can vary with the angle of the louvers. If you use the indirect airflow function, lower the louver angle as far as it will go.
4. Doors, windows and heat from outside. Hot air coming in through an open door or window, or an exhaust fan running at the same time, reduces the cooling. Close the curtains if sunlight comes straight in, as the Modena manual suggests.
5. After a power outage or unplugging. The Modena manual says the system waits about 3 minutes before it runs again, to protect the AC. Do not keep unplugging it and plugging it back in during that time.

A dirty filter is the easiest cause to fix yourself. LG says a dirty filter can reduce the cooling capacity and cause noise or condensation, and that performance gets worse as the weather gets hotter. Unplug the power cord, lift the front panel, then remove the fine filter the way your model's panel allows.

Clean it with a vacuum cleaner or a soft brush. If it is very dirty, wash it with diluted mild detergent and rinse it well; LG says the water should be no hotter than 40°C. Dry it in a shady, well-ventilated place, not in direct sunlight, and put it back only when it is completely dry. Special filters on some models, such as deodorizing or allergy filters, must not be washed with water and need replacing regularly.

As for how often, the Modena manual suggests cleaning the indoor filter whenever it looks dusty, within one or two months. Its troubleshooting section says the filter can be cleaned every month, depending on the location and how often the AC is used. Homes on a busy road or near a construction site usually need it more often.

The outdoor unit must be able to release heat. LG says to clear away anything stacked in front of, behind or around the outdoor unit and, if the unit sits in an enclosed space, to open its ventilation window wide. A unit in direct sun can overheat; a sturdy sunshade helps, as long as it does not block the back or sides of the unit. LG also says the AC may not work well when the outdoor temperature is below 18°C or above 48°C. Wearing gloves, you can brush the dust off the heat exchanger at the back of the outdoor unit with a stiff brush, from top to bottom. Take care not to bend the fins, and if you use water, spray it downward. The Modena manual suggests cleaning the outdoor condenser two or three times a year.

The power supply matters too. LG says the AC should not be plugged into a power strip or extension cord, but straight into a dedicated wall socket. A loose plug can overheat the cable and cut the power; LG suggests unplugging it, letting the cable cool for about 30 minutes, then plugging it back in firmly. The Modena manual gives the standard Indonesian household supply as 220V/50Hz, with a variation of about 10%, and asks for a single socket and a circuit breaker that match the ratings on the AC. If the voltage in your area often drops at peak hours, note when it happens for the technician.

A technician can find the fault faster if you give a clear picture. Before you contact the service center, note the following:

• since when the AC has not been cooling, and whether it happened suddenly or gradually;
• whether the outdoor unit's fan turns, and whether you can hear it running when the AC is on;
• whether the drain hose drips water as usual;
• whether a code or an indicator light blinks on the indoor unit, and in what pattern;
• when the AC was last cleaned or serviced, and what was done;
• whether the MCB has tripped, or the lights in the house dim when the AC starts.

A photo of the rating plate on the side of the indoor and outdoor units also helps, because it shows the model, capacity, refrigerant type and electrical requirements.

Contact a certified AC technician or the authorized service center for your brand if:

• the outdoor unit does not run, or the AC only blows cool air, even in cool mode at a low set temperature. LG says this needs a check for low refrigerant gas or a failed outdoor part;
• the AC is still not cold after the filter is clean, the outdoor unit has space, and the doors and windows are closed;
• there are burn marks on the socket or plug (LG says a qualified electrician should replace the socket);
• the outdoor fan does not turn, the unit hums but does not start, or the AC's MCB trips again and again;
• you suspect a refrigerant leak. Some units use a flammable refrigerant; the Modena manual names R32 and says to keep a leaking unit away from open flames. Open the windows.

Adding or recharging refrigerant, finding a pipe leak, replacing a capacitor or the compressor, and washing the evaporator by taking the unit's housing apart are jobs for a technician. The Modena manual states that refrigerant must only be added by a qualified technician.