Why air cons get mouldy, and how a clean fixes it

Mould in air conditioners is one of the most common things we see on the Sunshine Coast. Our humid climate is perfect for it, and once it takes hold inside a unit, it gets blown straight into the room every time you turn it on.

Why it happens

When your air con cools, moisture from the air condenses on the cold coil inside the indoor unit, the same way water forms on a cold drink. Add dust, warmth and a dark space, and mould has everything it needs. It’s worst after wet seasons and in homes near the coast, and in units that run on cool and then get switched straight off, leaving the inside damp.

Signs your air con has mould

• A musty or damp smell when it starts up

• Black or grey spots on the louvres or vents

• Sneezing, itchy eyes or a stuffy nose when it’s running

• Dark, slimy build-up you can see behind the front cover

What a proper clean involves

Cleaning the filters helps, but it doesn’t reach the mould. A professional clean usually involves:

• Opening up the indoor unit and protecting the wall and floor around it

• Washing the coil and the fan, where most of the mould hides

• Treating the unit to kill off what’s left

• Cleaning the drain tray and clearing the drain so water can’t sit and stagnate

• Reassembling and testing everything

The difference is easy to see. The water that comes out is often black.

How to keep it from coming back

• Clean your filters every few weeks when the air con is running a lot

• Use dry or dehumidify mode on humid days

• Run it on fan only for 10 to 15 minutes before switching off, so the inside dries out

• Book a service and clean at least once a year

Don’t spray household cleaners or disinfectants into the unit yourself. They can damage the parts and won’t reach the mould inside.

Smell something musty?

Get in touch to book a clean. We’ll get your system back to blowing fresh, clean air.