It is annoying to notice that the air from your air conditioner is lukewarm on the hottest day of summer. The first thought is that it is out of gas, but in a significant share of the calls we receive in the field, the problem is somewhere much simpler: a wrong mode, a clogged filter or an outdoor unit whose front has been blocked.
The seven checks below take a few minutes to do in order, and none of them requires touching the refrigerant circuit or the electrical panel. If there is still no cooling at the end, it is time to call service.
First, the remote and settings
01Is the mode really on cooling?
The snowflake symbol (Cool) should be selected on the remote. Fan mode (propeller symbol) only circulates the air, while dry mode (droplet symbol) runs the fan at low speed and cools the room slowly. In auto mode, the unit may choose fan or heating instead of cooling depending on the room temperature.
Also make sure the set temperature is at least a few degrees below the room temperature. If the set value is 26 °C and the room is 25 °C, the unit does not cool; it only runs the fan.
02Remote battery and timer
A weak battery can prevent the command from reaching the unit even if the setting shows on the remote's display. If the indoor unit does not beep when you give a command, replace the battery. Also, if sleep mode, eco mode or an off timer has been left on, the unit deliberately reduces its capacity or switches itself off.
Causes that block airflow
03Are the filters clogged?
A clogged filter is the most common reason an air conditioner does not cool. Lift the front panel and look at the filters; if there is a gray layer of dust on them, the air cannot pass through the coil sufficiently. In this case the outlet air is weak, the coil can get too cold and ice up, and cooling drops further.
Wash the filter with warm water and dry it in the shade, and put it back only after it is completely dry. We explained how often the filter should be cleaned in our air conditioner maintenance guide.
04Is the front of the outdoor unit clear?
The outdoor unit is the part that rejects the heat taken from the room to the outside; if its front is blocked, the heat cannot be rejected and cooling drops. Items placed in front of the outdoor unit on a balcony, a tarp covering it, and leaves and dust coating its fins have this effect. There should be at least a few tens of centimeters of clearance in front of and beside the unit.
If you want to wash the outdoor unit yourself, do it only from the outside, with low-pressure water and after cutting the power. Opening its cover and working on the inside is a technician's job.
05Is the room itself suitable for cooling?
Even if the air conditioner works correctly, the room will not cool if its capacity is not enough for the room. Large sunlit windows, doors and windows left open, an oven running in the same room or a lot of people increase the heat load. A small unit bought to cool the living room may fall short in the hottest hours; we explained how to choose the right capacity in our article how many BTU air conditioner should I buy.
Electrical and drainage checks
06Is the outdoor unit running?
If the indoor unit fan is running but the outdoor unit's fan is not turning and there is no compressor sound, there is no cooling. First check the fuse box to see whether the air conditioner's fuse has tripped. If it has tripped, you can reset it once; if it trips again, do not keep resetting it and call service.
After the compressor goes into protection, it waits for a while and restarts. After switching the air conditioner off and on, it can take a few minutes for the outdoor unit to start; this is normal.
No cooling despite the checks?
Our technician measures pressure, current and temperature difference on site and clearly tells you the cause of the fault and the solution options.
07Is there ice or water on the indoor unit?
If you see ice on the indoor unit's coil or on the copper pipes, switch the air conditioner off and wait for the ice to melt. Icing is usually caused by a clogged filter, low fan speed or low refrigerant. Melting ice can overflow the drain pan; if water is dripping from the indoor unit, you can find the causes in our article air conditioner leaking water.
When should you call service?
If there is still no cooling after the checks above, or if one of the symptoms below is present, you should call a qualified technician. These situations require work on the refrigerant circuit or the electronic board.
- The outdoor unit is running but lukewarm air comes from the indoor unit
- There is frost or an oily stain on the thin copper pipe at the outdoor unit
- The fuse keeps tripping or there is a burning smell
- An error code is blinking on the indoor unit's display
- A new sound such as rattling or humming comes from the outdoor unit
Refrigerant circulates in a closed circuit and normally does not decrease. If the gas has decreased, there is a leak somewhere; adding gas without finding the leak only postpones the problem. For this reason, the technician first measures the pressure with a manifold, finds and fixes the leak, then charges. For details, see our refrigerant leak and gas charging service.
What you should not do yourself
Some interventions made to solve a cooling problem make the fault worse and carry a safety risk. The jobs below should be done only by a qualified technician.
- Adding gas: Charging gas with cylinders bought online carries the risk of the wrong refrigerant or the wrong amount, and it hides the leak. Too much gas is as harmful as too little.
- Opening the outdoor unit cover: Behind the cover there is high voltage, a rotating fan and electricity stored in the capacitor.
- Resetting the fuse over and over: A fuse that keeps tripping points to a short circuit or a compressor problem; forcing it can burn the board or the compressor.
- Cleaning the coil with a hard brush: The thin aluminum fins get crushed and airflow is permanently reduced.
Keeping to this limit prevents a small fault from turning into an expensive compressor replacement. Your job is to describe the symptom accurately: noting when it started, which mode it was in and whether you saw an error code on the display speeds up diagnosis.
What does the technician measure?
During a service visit, the technician measures the operating pressures, the difference between the indoor unit's air inlet and outlet temperatures, the compressor current and the sensor values. In cooling mode, a difference of about 8-12 °C between inlet and outlet is generally expected. If the difference is clearly below this, low refrigerant, a dirty coil or compressor efficiency loss is investigated.
The YOİ Mühendislik team performs these measurements on site on all brands and clearly tells you the cause of the fault together with the repair options. The price is determined at the site survey according to the type of fault.
Frequently asked questions
Why does an air conditioner run but not cool?
The most common causes are a wrong mode setting, a clogged filter, an outdoor unit with its front blocked and low refrigerant. First check the mode, the filter and the outdoor unit; if the problem continues, a technician should take pressure measurements.
Does an air conditioner run out of gas?
Refrigerant circulates in a closed circuit and does not decrease in normal use. If the gas has decreased, there is a leak in the circuit, and the leak must be found and fixed first.
What should I do if the air conditioner's outdoor unit is not working?
Check the air conditioner's fuse in the fuse box and, if it has tripped, reset it once. If it trips again or the outdoor unit still does not work, call service without interfering with the electrical side.
How cold should the air from the air conditioner be?
In cooling mode, the air blown by the indoor unit is usually about 8-12 °C colder than the room air it draws in. If this difference has clearly decreased, the unit needs to be checked.