A bad smell coming from your air conditioner usually means something inside the air conditioning system is dirty, damp, blocked, or overheating. When an air conditioner smells bad, it affects indoor air quality, which can make your home uncomfortable during long periods of hot weather. The good news is that most unpleasant odours are fixable with the right approach.
Below, we break down the most common reasons an air conditioner might smell bad, how to get rid of those unpleasant odours safely, and how to prevent them from returning:
Why Does Your Air Conditioner Smell Bad?
Bad smells coming from your air conditioning unit are typically caused by moisture, dirt, or something trapped inside the AC system. Here are the most common culprits:
1. Mould Or Mildew Inside The Unit
When excess moisture sits in the evaporator coil, drain pan, or other hard-to-reach areas of the AC unit, mould or mildew can develop. This leads to a musty smell that many homeowners describe as “dirty feet”.
2. Clogged Or Dirty Air Filters
Dirty air filters restrict airflow and trap dust, pet dander, and cigarette smoke. When the air conditioner runs, it pushes air through those dirty filters, which can make the air smell musty, stale, or dusty. Dirty filters also cause the air conditioner to work harder, as well as reduce fresh air circulation inside the home.
3. Drainage Issues & Standing Water
If the drain line becomes blocked, water builds up in the drip pan. Standing water quickly turns into a breeding ground for bacteria and foul odours. This often creates an unpleasant smell that spreads through the air conditioning system every time the unit cycles on. If the unit sits unused for a long period, the smell may be stronger when it starts up again.
4. Dead Animals Or Debris In The Ductwork
Sometimes, a dead animal or outdoor debris can become lodged in the exterior components of the air conditioning unit. As the animal decomposes, the air conditioner smells bad due to the strong, lingering odour.
5. Electrical Or Burning Odours
A burning or electrical smell may indicate an overheated motor, worn wires, or another internal malfunction. This type of strange odour should never be ignored. Turn the unit off immediately. Burning smells can be related to mechanical friction or a failing part, which may create fire or health risks. If you smell gas or rotten eggs, leave the home immediately and contact your gas provider; this could signal a gas leak, not an AC problem.
How To Get Rid Of A Bad Smell From An Air Conditioner: 4 Simple Fixes
When your air conditioner smells bad, these simple steps can help you get rid of the smell and restore clean, fresh air:
1. Replace Or Clean Your Air Filter
A clogged air filter is one of the fastest ways for unpleasant odours to come through your air conditioning system. Replacing the filter often resolves musty or dusty smells quickly. If your unit uses a washable filter, rinse it with warm water and let it dry completely before reinstalling it.
Clean filters help improve indoor air quality and support better airflow throughout your home. Regularly changing the air filter also protects the evaporator coil from dirt buildup.
2. Inspect For & Remove Mould Or Mildew
Carefully inspect the accessible parts of the AC unit for signs of mould growth or mildew growth. Look around the evaporator coil, drain pan, and areas where condensation tends to form. If you find any dark or slimy patches, you can gently wipe them with a cloth and a mild cleaning solution.
If the mould is heavy, covers a large surface, or is deep inside the system, contact a professional technician. Mould can cause health risks when disturbed. A technician can remove the mould safely and check for the source of excess moisture.
3. Use A Natural Odour Absorber (Like Baking Soda)
If the air conditioner smells but there is no obvious dirt or blockage, a natural odour absorber can help. Try placing a small dish of baking soda near the indoor unit. Baking soda neutralizes lingering bad smell issues without adding chemicals to your home.
You can also use an air purifier to help reduce unpleasant odours while improving overall air quality.
4. Schedule Regular AC Maintenance
Routine inspections prevent small problems from turning into mechanical failure or foul odours. During a maintenance visit, a professional technician checks wiring, drainage, refrigerant levels, the evaporator coil, and other components prone to problems. Regular maintenance also helps reduce the risk of a refrigerant leak or mechanical issue that may cause a strange odour.
Since AC units handle moisture, heat, and airflow, seasonal checkups are vital for preventing bad smells and keeping the unit running efficiently.
How To Prevent Bad Smells In Your AC System
Preventing bad smells in your air conditioning system is easier than dealing with them later. These habits help keep your home’s air fresh and clean:
Replace the air filter on a regular schedule.
A clean air filter supports better airflow, reduces dust buildup, and helps prevent unpleasant odours from returning.
Keep the area around your air conditioning unit clean.
Remove leaves or debris from around the outdoor unit. This helps prevent small animals or nesting materials from getting inside.
Run the AC in fan mode occasionally.
This helps dry out moisture after a humid day. Removing extra moisture minimizes the risk of mould or mildew forming inside the unit.
Watch for signs of excess moisture.
If you spot water around the drip pan or condensation forming on nearby surfaces, the AC system may not be draining correctly. Catching this issue early helps avoid bad smells later.
Avoid storing items that carry strong smells near the indoor unit.
For example, cigarette smoke or chemical cleaners directly beside the AC intake can cause those scents to circulate through the home.
Pay attention to electrical smells.
A burning smell or hot metal scent means the AC should be shut off immediately. Call a technician to inspect the unit before running it again.
Conclusion: Keep Your AC Smelling Fresh All Season
Bad smells coming from your air conditioner are usually caused by moisture issues, dirty air filters, mould growth, and/or mechanical problems inside the unit. The fastest way to get rid of bad smells is to replace the air filter, remove mould or mildew, use a natural odour absorber, and schedule regular maintenance with a qualified technician. These steps help improve indoor air quality and keep the air in your home feeling clean and fresh throughout the summer.
If you want your air conditioning system to run smoothly and be odour-free, Provincial Heating & Cooling is here to help. For dependable service and expert advice on air conditioning Winnipeg homeowners trust, contact our team today.