Aircon troubleshooting at home comes down to a few safe checks before you book anyone: power, remote settings, filters and the outdoor unit. None of them needs tools or opening the casing. If one of them solves it, you have saved a visit. If not, you can tell the technician exactly what you have already ruled out.
This page covers the checks only. For what each symptom usually means, see the list of aircon problems.
Check the power first
Find the isolator switch for the unit. It is a separate wall switch, often near the indoor unit or next to the outdoor unit. Make sure it is on. Then open the DB box (the distribution board) and look for a breaker that has dropped.
You can push a tripped breaker back up once. If it drops again, leave it off. A breaker that keeps tripping points to an electrical fault, and resetting it again and again does not fix it. More on this under aircon keeps tripping the breaker.
If the power is on and the indoor unit gives no light and no beep, the fault is inside the unit. Go to aircon not turning on.
Look at the remote and its settings
Change both batteries first. A remote with weak batteries can still light up its screen and never reach the unit.
Then check the mode. On most remotes the snowflake icon is cooling. A water drop means dry mode, which takes moisture out of the air but cools much less. A fan icon only moves air around.
The set temperature has to be below the room temperature, otherwise the compressor has nothing to do. Look at the timer too. An off-timer left on from a previous night switches the unit off at the same time again. On many models, sleep mode raises the set temperature step by step through the night, and that can feel as if the aircond has stopped cooling.
If the settings are right and the room still will not cool, read aircon not cold.
Wash the filters
- Switch the unit off with the remote, then at the isolator.
- Lift the front panel and slide the filters out.
- Rinse them under the tap from the back, so the dust leaves the way it came in.
- Let them dry completely in the shade. A filter that goes back in damp will start to smell.
- Slide them back and press the panel down until it clicks.
When the filters are clean and the airflow is still weak, the dirt sits deeper, on the coil or the blower wheel, where a rinse does not reach. That is a job for a chemical wash service. The page on weak airflow explains the causes.
A musty smell that stays after the filters are washed usually comes from mould further inside. See bad smell from the aircon and mould inside the aircon.
Check the outdoor unit
The outdoor unit is where the heat from your rooms goes out. When it cannot get rid of that heat, the indoor unit blows air that is only slightly cool. Move anything stacked against it, such as a laundry rack or boxes on the balcony.
With the aircon set to cool, the outdoor fan should be turning. If the indoor unit runs while the outdoor unit stays silent, switch everything off and read outdoor aircon unit not running.
Ice on the coil or the copper pipes
Ice means the unit is not moving enough heat. Turn cooling off and run fan mode until the ice has melted, then wash the filters.
If the ice is back within a day, the cause is deeper: a dirty coil, or low gas. Gas does not get used up like petrol. If the level is low, it has leaked out somewhere, and the leak has to be found before any gas top-up.
Indoor unit dripping water
Switch the unit off and put a towel or a basin underneath. If you can see where the drain hose ends outside, check that the end is not squashed flat or sitting in water.
When the hose end is clear but the dripping goes on, the blockage is inside the drain pan or the line. That is covered on aircon leaking water. Water running down the wall from a water pipe, not from the aircon drain, is a plumbing problem. That falls under pipe leak repair.
An error code on the display
Write the code down, or film the blinking light so you can count the flashes. Switch the unit off at the isolator, wait about five minutes and switch it back on.
If the code clears and stays away, it was a one-off. If it returns, a sensor or the control board is reporting a real fault, which is covered under PCB and control board repair. Take a photo of the sticker on the side of the indoor unit as well. It shows the brand and model, and the technician needs both to read the code.
Noise
A rattle that started right after you cleaned the filters is often the front panel sitting loose. Press along its edges until it clicks in.
A grinding or squealing sound from inside the unit is different. Switch it off and read aircon making noise. If the unit shakes or hums, the fan may need fan motor repair.
When to stop and leave it off
Stop checking and keep the unit switched off if:
- you smell burning or see sparks
- the breaker trips a second time
- water is dripping close to a socket or the isolator
- an error code comes back after the reset
Do not open the casing or touch any wiring.
Before you message us
If the checks did not fix it, send us what you found on WhatsApp. It saves a step at the visit. Helpful details:
- which room, and whether the unit is wall-mounted or a ceiling cassette
- what you have already checked on this page
- the error code or the number of flashes, if there is one
- a photo of the model sticker
- your area in KL
You can also use our contact page to reach a technician. Not sure which service you need? Our FAQs explain aircon repair, chemical wash and servicing in plain terms, and the main aircon service page for Kuala Lumpur lists everything we do.