Aircon Compressor Not Working? Signs, Causes and What to Do Next

The fan is running, air is coming out, and it’s about as cold as a warm afternoon on the MRT platform. When an aircon blows but doesn’t cool, people often suspect the compressor, the outdoor unit that does the heavy lifting. Sometimes they’re right. Often it’s a much cheaper part.

Signs the compressor isn’t running

• The indoor fan blows, but the air isn’t cold
• The outdoor unit stays silent when the aircon is on
• The outdoor fan spins, but the room never cools
• You hear clicking from the outdoor unit, then it stops
• The power trips whenever the aircon tries to start

Safe checks to try first

1. Check the remote is on cool mode, not fan or dry.
2. Check the isolator switch is on.
3. Wash the filters.
4. Clear anything blocking the outdoor unit, such as laundry racks or boxes.
5. Switch off, wait five minutes and try again. Many compressors have a built-in delay after a restart.

Stop there. Don’t open the outdoor unit yourself, because the parts inside carry a charge even after you switch it off.

Common causes

A failed capacitor. It gives the compressor its starting kick. It’s a common fault and a small part.

Contactor or PCB faults. The compressor may be fine but isn’t being told to start.

Low gas. Many systems protect themselves by not running when the pressure is off. Gas needs checking with a gauge.

A dirty outdoor unit. If it can’t release heat, it overheats and cuts out. A compressor wash can help. It’s included for the first unit in our Deluxe General Servicing and BeeChem Wash™, and with BeeChem Wash™ each extra compressor is an $18 top-up.

A worn-out compressor. This does happen, usually on older units. It’s the most expensive fix, so make sure the cheaper causes have been ruled out. Our guide on repair or replace can help you decide.

Not sure it is the compressor? An aircon servicing visit lets us look at the whole unit.

Suspect low gas? See aircon gas top-up for how we check the pressure and what a top-up costs.

Our diagnostic fee is SGD 50, waived with the repair (T&C apply). See aircon repair, WhatsApp us, or book online.