AC not cooling? Common causes and what to do
AC running but blowing warm air? Five quick checks in 15 minutes, a symptom table, and typical UAE repair prices for gas, capacitors, fan motors and compressors.
When an AC runs but blows warm or barely cool air, the cause is often a wrong setting, dirty filters or a blocked outdoor unit, and all three can be checked in about 15 minutes. If the air is still warm after that, the likely cause is low refrigerant gas from a leak, a dirty coil, a failed capacitor or compressor, a unit too small for the room, or, in buildings on district cooling, a problem with the chilled water supply. Those need a technician or the building management.
Check these first
These checks are safe and need no tools.
- Mode and temperature. The remote or thermostat should show Cool, not Fan, Dry or Auto, with a set temperature clearly below room temperature, for example 23–24°C. Faint displays need new batteries, and sleep or eco modes are best switched off for the test.
- Filters. Washing dusty filters and waiting 15 minutes often restores airflow. After a sandstorm, filters can clog within days.
- Outdoor unit. On a split system, the outdoor unit needs free space around it: no boxes, covers, plants or sand drifts. Its fan should spin and blow warm air out.
- Doors, windows and sun. Closed doors and windows and drawn blinds against the afternoon sun make a big difference in summer.
- After a power cut. Many units wait a few minutes before the compressor restarts. A wait of 5–10 minutes comes before any conclusion.
The unit should not be opened, and the wiring and refrigerant are not for home repairs. The outdoor unit holds electrical parts that stay charged, and handling refrigerant needs proper tools and training.
Read the symptoms
| What happens | Likely cause | Who fixes it |
|---|---|---|
| Weak airflow from the indoor unit | Dirty filters or dirty indoor coil | Filters at home; coil by a technician |
| Strong airflow, but the air is only cool, not cold | Low gas, dirty coils or an undersized unit | Technician |
| Ice on the indoor coil or the copper pipes | Very low airflow or low gas | Technician (unit off until the ice melts) |
| Outdoor fan not spinning, humming or clicking | Capacitor, contactor or compressor | Technician |
| Error code or blinking lights | The unit has detected a fault | Technician (a photo of the code helps) |
| Cold in the morning, warm every afternoon | Undersized unit, strong sun or dirty outdoor coil | Technician or a larger unit |
| Fan coil runs but the air is not cold, in a chiller building | Chilled water supply, valve or thermostat | Building management first |
Causes that need a technician
Low refrigerant gas
An AC is a sealed system and its gas does not get used up. Low gas means a leak. A good technician finds and fixes the leak first, then recharges. A top-up without a leak check often means the room is warm again within weeks, and the bill is paid twice.
Dirty coils
Dust and humidity coat the coils, so heat cannot leave the room. If the last service was more than 6 months ago, AC cleaning comes before any repair. Units that smell musty or have gone a year without service may need a deep coil clean.
Capacitor, contactor or compressor
The capacitor helps the compressor and the outdoor fan start, and it often fails in summer heat. A capacitor or contactor is a fairly small repair. A failed compressor is the most expensive one, and on an older unit a technician may suggest comparing the repair price with a new unit.
Unit too small for the room
A 1 ton unit in a large, west-facing room or a top-floor room under a hot roof will run all afternoon and never feel cold when it is 45°C outside. Nothing is broken; the unit is undersized. The guide on what size AC is needed shows the right capacity before money goes into repairs.
District cooling buildings
In apartments on district cooling, the fan coil unit only blows air over pipes with chilled water from the building. If the fan runs but the air is warm, the cause can be a closed valve, a faulty thermostat or the supply itself. The building management or facility team should be the first call; a private technician cannot add gas to this type of system.
What it costs
| Service | Typical price in the UAE |
|---|---|
| Inspection or diagnostic visit | AED 50–250, often deducted from the repair |
| Standard AC cleaning | AED 150–250 per unit |
| Gas top-up, split unit | AED 250–450 |
| Leak detection, repair and recharge | AED 600–1,200 |
| Capacitor replacement | AED 180–350 |
| Fan motor, indoor or outdoor | AED 450–1,100 |
| Control board (PCB) | AED 600–1,600 |
| Compressor, 1.5–2 ton split | AED 1,800–3,800 |
Labour is often charged at about AED 150 per hour, with parts on top. A unit that cools poorly also runs longer: the AC electricity cost calculator shows what that adds to the bill.
What to tell the technician
- Brand, type (split, ducted or concealed, window), inverter or not, and the size in tons from the label.
- Age of the unit and the date of the last service.
- What happens: warm air, weak air, ice on the pipes, noises, a tripping breaker.
- Any error code, with a photo.
- Where the outdoor unit is (balcony, roof, ground) and whether the building needs a work permit.
It is worth asking what the visit fee is, whether it is deducted from the repair, and whether a leak check comes before any gas is added.
If the quick checks did not help, the symptoms can be described once on khalasna to compare quotes from up to 5 AC repair companies, for example in Abu Dhabi, with the visit fee and warranty clear before anyone arrives.
Frequently asked questions
Why is the AC fan running but the air is not cold?
The compressor or the cooling supply is not doing its job. Common reasons are low gas from a leak, a weak capacitor, very dirty coils, a blocked outdoor unit or, in chiller buildings, a closed valve or a supply problem.
Why does the AC cool at night but not in the afternoon?
Afternoon sun on walls, windows and roofs adds a lot of heat. If cooling drops every afternoon, the unit may be undersized, the outdoor coil may be dirty, or the outdoor unit may sit in direct sun with poor airflow.
Will adding gas make the AC cold again?
Only after a leak check. Refrigerant does not get used up, so low gas means a leak, and a top-up without a repair usually wears off within weeks or months.
Is it safe to keep using an AC that is not cooling?
Short use is fine, but the unit should be switched off if ice forms on the pipes, a loud hum or clicking starts, or the breaker trips. A struggling unit raises the bill and can damage the compressor.