Air Conditioner Smells? Here’s How to Identify and Fix the Problem

Common Air Conditioner Smells, Their Causes, and How to Fix Them

Turning on the air conditioner should bring instant relief, not an unpleasant smell throughout your home. When your AC produces a strange odour, it’s usually an early sign that something isn’t working properly. Dust, moisture, electrical issues, or restricted airflow can all cause smells that impact comfort and indoor air quality.

Some air conditioner smells are harmless and easy to resolve, while others point to serious issues like mould growth, electrical faults, or refrigerant leaks that need urgent attention. This guide explains the most common AC smells, their causes, how to fix them safely, and when to call a licensed technician with advice tailored for Adelaide homes and changing seasonal conditions.

Why does my air conditioner stink?

Air conditioners constantly pull in air along with moisture, dust, and airborne particles. Over time, this build-up inside the system leads to unpleasant smells.

Common causes include:

• Bacteria and mould growth form on damp coils, filters, or drip trays
• Blocked drain lines are causing water to pool and stagnate inside the unit
• Electrical overheating from worn wiring, motors, or internal components
• Trapped debris, such as leaves, insects, or small rodents, in outdoor units
• Refrigerant leaks are releasing chemical odours

In many cases, the smell is the first warning sign that something isn’t right. Catching the issue early can help prevent system breakdowns, health risks, or expensive repairs later on.

7 Unpleasant Air Conditioner Smells

1. Mould and Mildew Smells

A musty smell from your air conditioner usually means mould or mildew is growing inside the unit, ducts, or drain tray due to trapped moisture. Mould spores can reduce indoor air quality and trigger allergies or asthma if left untreated. In Adelaide, this can occur after winter shutdowns, from blocked drains, or leftover moisture from evaporative cooling systems.

How to Fix It

• Replace or clean the air filter
• Check for water pooling around the indoor unit
• Book a professional internal clean if the smell persists

2. Dirty Socks Smell

A dirty socks smell, often called “dirty sock syndrome,” is caused by bacteria building up on the evaporator coil, usually after the air conditioner has been sitting unused for a long period.

How to Fix It

• Replace or clean the air filters
• Schedule a professional coil clean with antibacterial treatment
• Run the fan-only mode occasionally to help dry out internal components and prevent moisture buildup

3. Electrical Burning Smell

A burning smell from your air conditioner is a serious electrical warning sign. It’s commonly caused by overheated wiring, failing circuit boards, or issues with the motor or capacitor.

What to do immediately:

• Turn the system off at the wall
• Do not continue using the unit
• Call a licensed air conditioning electrician straight away

4. Sweet Chemical Smell

A sweet chemical smell coming from your air conditioner indicates a refrigerant leak, such as R-410A or R-32. This is not something that should be handled without proper licensing. Prolonged exposure to refrigerant can cause headaches, dizziness, and breathing difficulties, so this issue should be addressed promptly.

How to fix it:

• Turn off the air conditioning system
• Ventilate the area by opening windows and doors
• Contact a licensed technician to inspect and repair the leak

5. Rotten Egg or Sulphur Smell

A rotten egg smell is a serious issue that should never be ignored. It can be caused by an external gas source entering the ductwork, sewer gas infiltration, or even a dead animal near the unit.

What to do:

• Turn off the air conditioning system immediately
• If the smell is strong or doesn’t go away, evacuate the property
• Contact an emergency licensed professional to investigate and make the area safe

6. Cigarette Smoke Smell

A cigarette smoke smell in your air conditioner occurs when smoke particles get trapped in the filters, coils, or ductwork, then recirculate through your home.

How to fix it:

• Replace air filters more frequently
• Schedule a deep professional system clean
• Avoid smoking near indoor or outdoor units to prevent residue buildup

7. Dead Animal or Garbage Smell

A foul, decaying smell from your air conditioner usually means a rodent, bird, or other pest has become trapped in the ductwork.

How to fix it:

• Stop using the air conditioner immediately
• Arrange professional removal and sanitisation of the unit
• Seal any access points to prevent pests from entering again

Why Regular Air Conditioner Maintenance Important

Most air conditioner smells can be prevented with routine servicing. Regular maintenance helps to:

• Improve airflow and system efficiency
• Extend the lifespan of your AC unit
• Reduce electricity costs
• Protect indoor air quality
• Prevent costly emergency repairs

In Adelaide’s hot summers, a poorly maintained air conditioner has to work harder, which can lead to faster wear and unexpected breakdowns. Regular checks keep your system running smoothly and smelling fresh.

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Read more: How Often Should You Service Your Air Conditioner?

Book an Air Conditioning Inspection From Aquila Electrical

Unpleasant air conditioner smells are an early warning of underlying issues like mould, bacteria, electrical faults, or refrigerant leaks. Ignoring these odours leads to reduced indoor air quality, higher energy bills, and even serious safety risks. Identifying the type of smell and addressing it promptly is the key to keeping your home comfortable, safe, and healthy throughout Adelaide’s hot summers.

The best way to prevent and resolve air conditioner smells is through regular maintenance and professional inspections. If your air conditioner is producing strange odours, Aquila Electrical can help. Our Licensed Electrician provides expert air conditioning services across Adelaide, from system diagnostics and repairs to deep cleans and refrigerant handling. Contact Aquila Electrical today to schedule an inspection and keep your air conditioner running efficiently and smelling fresh all year round.

📞 Call us on 0488 551 630

‍📍 Based in Hove, SA 5048