How to get rid of a musty smell in your air conditioning

In the hot Australian climate, there is only one thing worse than not having a car air conditioner – and that is having an unpleasant musty smell coming from your air vents.

The unpleasant odour will affect your comfort every time you turn the air conditioner on. Odours in a car’s air con system can come from a few different sources. For example, your air filters could be dirty, or air conditioner gas could be leaking. However, one of the primary causes of odour from air conditioning systems is mould.

What is the problem with mould?


The most obvious problem is the musty smell, which mould gives off causing discomfort for passengers. The more the mould is allowed to spread, the worse the problem becomes.

Spreads quickly

As a fungus, it can spread rapidly and become imbedded in floor carpets and even into the upholstery. In the long term, that means that even if the root cause is solved, a mould problem that is left for longer can leave spores and a musty smell in the car behind.

Impact to health

  • Nasal congestion
  • Throat irritation
  • Wheezing
  • Irritation to the eyes
  • In extreme cases, it can reduce lung function and cause long term health problems such as asthma

The Centre for Disease Control and Prevention (CDC) highlights the severe reactions possible for people with mould allergies.

For both comfort and health, it is important to deal with mould in your car air conditioner.

mouldy car air conditioning fix

What causes mould to grow in the air conditioning system?

Mould is a fungus that thrives in moist places. Wherever there is a presence of moisture and organic nutrients, there is a high possibility for mould to grow.

One of the things a car air conditioning system does is remove moisture from the air. Here’s how:

  • While the air is being cooled by the evaporator, moisture condenses out of the air.
  • By design, this moisture is collected and drained out of the vehicle. It is the reason why you often find a wet patch under the car after you have driven it with the air conditioner running.
  • Of course, when something goes wrong with the water drainage system, it can overflow into the car leading to damp conditions – the ideal environment for mould to grow.

Unfortunately, as the evaporator is out of sight, a problem with water drainage may not be immediately obvious. You may only become aware of the problem after mould begins to grow due to the moisture build up behind the dash panel.

How to get rid of mould in car air conditioning

Once you have identified mould as the source of your musty smell, there are some practical steps you can take to remove it.

1. Dry out your car. Because mould thrives on moisture, the number one thing you can do is remove moisture from the car. Park your car in direct sunlight and leave the doors and windows open. This will provide the heat and air movement necessary to evaporate moisture from the vehicle.

2. Use an anti-bacterial treatment. Anti-bacterial products kill the mould fungus and so if you treat all the areas where mould could grow, especially around the evaporator, you will help to eliminate the source of the smell.

3. Check your air filters. It is possible for mould to grow in the air filters themselves if the conditions are right. Cleaning or replacing air filters on a regular basis is a good idea for health and odour reasons.

While these steps can help to remove mould from your vehicle, they may not solve the root cause of the problem. Unless you deal with the build-up of moisture in the air conditioning system, the problem will reoccur.

How can I get rid of mould in my air conditioning for good?

It is a good idea to have your air conditioner serviced if you are experiencing mould problems. This will deal with the source of moisture and will help prevent the growth of mould in the first place.

Service technicians will check and clear the water drainage system around the evaporator, ensuring water is removed from the vehicle and cannot be the cause of moisture problems.

Ask Natrad for air conditioner diagnosis and repair. We can service and repair your car air conditioner, so get in touch before mould becomes a serious problem.