Why Does My Evaporative Cooler Smell Bad?

If your evaporative cooler smells bad when you turn it on, you are not alone. This is one of the most common evap cooling issues Melbourne homeowners experience, especially at the start of summer or during hot, humid weather. January and February in Melbourne’s northeastern suburbs, such as Eltham, Epping, Greensborough, and Fairfield, can become extremely humid. And this is when evaporative air cons get the biggest workout. If you switch it on and then are met with a musty or rotten egg smell, it’s a sign that something is wrong. 

In most cases, the problem is easy to fix when addressed early. Left too long, it can affect air quality, cooling performance and even your health. Below, Harley Plumbing explains why evaporative coolers smell bad, what the different smells mean, and what you should do to fix the problem.

Common Reasons Your Evaporative Cooler Smells Bad

Dirty or Worn Cooling Pads

Cooling pads play a major role in evap cooling. Over time, dust, dirt and minerals from water build up inside the pads. When water runs over dirty pads, it can create unpleasant odours that spread throughout your home.

If your evap cooler smells musty or earthy, worn or dirty pads are often the cause. Pads usually need replacing every few years, depending on usage and water quality.

Stagnant Water Inside the System

Evaporative coolers rely on water to operate. If water sits in the system for long periods without draining, bacteria and algae can grow.

This commonly happens when:

• The system has not been used for months
  
• The cooler was not drained properly at the end of last season
  
• The drain valve is not working correctly
  

Stagnant water often causes smells similar to rotten eggs or stagnant ponds.

Lack of Regular Servicing

Yes, it’s a boring answer, but most likely this is the reason your evap cooler is acting as a stinky perfume spray rather than blowing fresh cool air. We recommend a service every year or two. Whilst it’s a good idea to book a service before summer, we get that people overlook it. So, if you switch on your air con and it sticks to high heaven or just has an unpleasant odour, give us a call and we will get to you asap. 

Mould, Bacteria or Algae Growth

Warm temperatures and moisture create the perfect environment for mould and bacteria. These microorganisms can grow inside the unit, on pads, in water trays and within ducts. If your evaporative cooler smells mouldy or sour, there may be microbial growth present. This is not something that should be ignored, as it can impact indoor air quality. We are not health experts, but breathing in bacteria and mould generally isn’t viewed as a healthy environment, especially for kids and the elderly. So we encourage servicing to avoid this. 

Is It Safe to Run an Evaporative Cooler That Smells?

In some cases, mild odours may disappear after the system runs for a short time. However, strong, persistent or unpleasant smells are a warning sign.

Running a smelly evaporative cooler can:

• Circulate bacteria and mould spores through your home
  
• Trigger allergies or respiratory irritation
  
• Indicate internal damage or poor water quality
  

If the smell does not improve quickly, it is best to stop using the system and have it checked by a professional.

How to Fix a Smelly Evaporative Cooler

There are a few basic things you can check safely:

• Run the system in fan-only mode for a short time
  
• Check for obvious debris around vents
  
• Ensure the unit has been fully drained if it has not been used recently
  

Avoid opening the unit or handling internal components unless you are trained, as this can cause damage or void warranties.

Professional Cleaning and Servicing

A professional evaporative cooler service includes:

• Cleaning or replacing cooling pads
  
• Flushing and disinfecting water trays
  
• Checking water distribution and drainage
  
• Inspecting overall system performance
  

This not only removes odours but also improves cooling efficiency and extends the life of the system.

How to Prevent Evaporative Cooling Smells

Preventing bad smells is easier than fixing them after they develop.

To keep your evap cooler fresh:

• Book professional servicing at least once a year
  
• Replace cooling pads when recommended
  
• Drain the system properly at the end of summer
  
• Run the system periodically during the season to avoid stagnant water
  
• Address minor smells early before they worsen
  

Regular maintenance saves money and helps avoid breakdowns during peak heat.

When to Call Harley Plumbing

You should contact Harley Plumbing if:

• The smell is strong or keeps returning
  
• Your evap cooler is not cooling properly as well
  
• The system has not been serviced in several years
  
• You are unsure of the system’s condition or age
  

Our experienced team can diagnose the cause quickly and recommend the right solution to restore clean, reliable cooling.

Final Thoughts

If you are wondering why your evaporative cooler smells bad, the issue is usually linked to water, cleanliness or maintenance. While it may seem minor at first, unpleasant smells are often an early warning sign that your system needs attention.

Addressing the problem early helps protect your indoor air quality, improves performance, and avoids costly repairs.

Harley Plumbing provides professional evaporative cooling servicing and repairs to keep your system running clean and efficient. Contact us today to book a service or inspection.