Air conditioner not cooling: 8 possible causes
- Mode and set value: the remote may have been left in fan, dry or heating mode, or the set value may be high.
- Dirty filter: airflow drops and cooling weakens.
- Outdoor unit blocked or coil dirty: heat cannot be rejected, the unit's efficiency drops and it may go into protection mode.
- Insufficient capacity: the BTU value chosen for the room may be too low. To check: air conditioner BTU calculation.
- Low refrigerant: there is a leak somewhere; the indoor unit blows lukewarm air and icing may appear on the pipes. See air conditioner gas charging.
- Outdoor unit fan fault: if the fan is not turning, the compressor shuts off on high pressure.
- Compressor or capacitor fault: the outdoor unit may make noise as if running but not cool.
- Board or sensor fault: usually seen together with an error code. See air conditioner error codes.
Is your air conditioner not cooling?
Tell us the brand, model, symptom and the error code if there is one; we will schedule a team for a measurement-based fault diagnosis.
Checks you can do yourself
- Select the cooling (snowflake) mode on the remote and set the temperature a few degrees below the room temperature.
- Clean the filters.
- Clear the front and top of the outdoor unit and listen to check whether it is running.
- Make sure the doors and windows are closed.
- If there is an error code on the display, note it down.
If cooling does not improve after these checks, call service. Gas, electrical and compressor work is for the technical team.
If the air conditioner is not cooling and is leaking water
If both symptoms are present together, the coil icing up and then thawing because of low refrigerant or a very dirty filter is a possible cause. Details: air conditioner leaking water.
Frequently asked questions
Why does an air conditioner blow hot air?
The remote may be in heating or fan mode; if the mode is correct, low refrigerant, an outdoor unit fan fault or a compressor fault should be considered.
The air conditioner is running but not cooling, is it out of gas?
It may be, but first the filter, the mode setting and the outdoor unit should be checked. Low refrigerant is confirmed by a pressure measurement and always means a leak.
What should I do if the outdoor unit is not working?
Check the fuse and the remote mode; if the outdoor unit still does not work, there may be a board, capacitor or compressor fault. Call service.
Why is my air conditioner not enough in summer?
The capacity may be too low for the room, or the outdoor unit may be in a very hot, unventilated place. You can check with a capacity calculation.