Why Is My AC Not Cooling? 9 Common Causes in Dubai Homes
By the Top Tier Technical Services team · Published · 7 min read
Quick answer
An AC that runs but doesn't cool is most often caused by a dirty filter, dirty coils, a blocked or overheating outdoor unit, or low refrigerant from a leak. Wrong thermostat settings, a frozen coil, a blocked drain, electrical faults and leaking ducts are the other common causes.
Key takeaways
- Check the simple things first: the mode and temperature setting, the remote's batteries and the filter.
- The U.S. Department of Energy says routinely cleaning or replacing filters can lower an air conditioner's energy use by 5–15%.
- Low refrigerant means there is a leak. It should be found and repaired, not just topped up.
- Ice on the pipes or coil, a burning smell, or a tripping breaker are signs to switch the AC off and call a technician.
What should you check first when your AC is not cooling?
Start with the checks that take a minute and need no tools. A surprising number of "broken" air conditioners are set to the wrong mode or have a filter full of dust.
- Check the remote or thermostat is set to Cool (not Fan, Dry or Auto), with a temperature below the room temperature.
- Replace the remote's batteries if the display is faint or the unit doesn't beep when you press a button.
- Open the indoor unit's front panel and look at the filter. If it is grey with dust, clean it.
- Go outside and check the outdoor unit is running: you should hear it and see the fan turning.
- Check the breaker for the AC hasn't tripped.
If none of these fixes it, one of the causes below is likely.
What are the most common causes of an AC not cooling?
1. Wrong thermostat or remote settings
Fan mode only moves air, and Dry mode cools very little. A thermostat that is reading the wrong temperature, for example because it sits in direct sun, can also stop the AC from cooling properly.
2. A dirty filter
A clogged filter restricts airflow, which reduces both cooling and efficiency. The U.S. Department of Energy says routinely cleaning or replacing filters can lower an air conditioner's energy use by 5–15%. In Dubai's dusty conditions, filters fill up quickly during heavy summer use.
3. Dirty coils
The indoor coil absorbs heat from the room and the outdoor coil releases it outside. When either is coated in dust, the heat transfer drops and the AC runs longer without reaching the set temperature. Coil cleaning is part of a proper AC service.
4. A blocked or overheating outdoor unit
The outdoor unit needs space to release heat. Boxes stored against it, sand blocking the fins, or a unit in a tight, unventilated spot can make it overheat and cool poorly, especially on the hottest afternoons.
5. Low refrigerant (gas) from a leak
Refrigerant doesn't get used up. If it is low, there is a leak somewhere. A technician should find and repair the leak and then recharge the system. Topping up without fixing the leak only works until the gas escapes again.
6. A frozen evaporator coil
Ice on the indoor coil or on the copper pipes is usually caused by restricted airflow (a dirty filter or coil) or low refrigerant. Switch the AC to Fan mode or off to let it thaw, then have the cause fixed.
7. A blocked drain
A clogged condensate drain makes the indoor unit leak, and on some systems a safety switch stops the cooling when the drain pan fills up. See our guide to water leaking from a split AC.
8. Electrical and control faults
Worn compressor and fan controls, a failed capacitor or a faulty control board can stop the compressor or outdoor fan from starting. These need a technician to test the electrical parts safely.
9. Leaking or blocked ducts
In ducted and central systems, cold air can escape through leaking ducts or be held back by dust and debris before it reaches the room. Rooms at the end of a long duct run are usually affected first. Our AC duct cleaning service deals with this.
When should you call an AC technician?
Switch the AC off and book a technician if you notice:
- Ice on the pipes or the indoor coil
- A burning smell, or a breaker that trips again after you reset it
- The indoor fan running but the outdoor unit silent (see split AC not cooling but the fan is running)
- Hissing or bubbling sounds, which can point to a refrigerant leak
- Weak cooling that continues after cleaning the filter
Our technicians diagnose the cause before any work starts, then clean, repair or recharge the system as needed. See our AC maintenance and repair service or contact us to book.
Frequently asked questions
Should I switch off my AC if it's not cooling?
If there is ice on the pipes, a burning smell or a tripping breaker, switch it off straight away. Otherwise, check the settings and filter first. If it still won't cool, switch it off and book a technician rather than leaving it running.
Can low AC gas just be topped up?
Refrigerant doesn't get used up, so low gas means there is a leak. The leak should be found and repaired before the system is recharged, otherwise the gas escapes again.
Why does my AC cool at night but not in the afternoon?
In the afternoon the heat load is at its highest. A dirty filter or coil, an outdoor unit in direct sun with poor airflow, or low refrigerant can leave the AC just able to cope at night but not in peak heat.
How often should an AC be serviced in Dubai?
For units running most of the year, a thorough AC cleaning every three to four months is a sensible schedule, because dust and sand clog filters and coils faster than in milder climates. Clean washable filters more often during summer.
Can a dirty filter really stop an AC from cooling?
Yes. A clogged filter restricts airflow, which reduces cooling and can cause the indoor coil to freeze. Cleaning it is the first thing to try.