5 Common Air Conditioning Smells and Their Surprising Causes

With the weather starting to heat up after a relatively chilly winter, many of us will be making use of our air conditioners over the coming months.

If you’ve not used your air conditioner to heat your home over winter, chances are you’ve likely not used it since last summer. So, if you notice some funny air conditioning smells coming from your split system or ducted unit, there’s likely something not quite right.

Often there can be a variety of reasons why your air conditioner smells bad. It could be anything from bacterial growth build-up to fried circuits.

It may also simply indicate that your dirty air filters need cleaning or replacing. Whatever the situation, air conditioner smells can point to a severe problem that needs prompt investigation from a licensed air conditioning technician.

Here are five of the most common air conditioning system smells and their causes.

1. Mould and Mildew Air Conditioner Smells

If your smelly air conditioner emits a stale or musty smell around the house, it could result from a leak somewhere in the system.

It’s not uncommon for the drip lines, drain pan or evaporator coils to clog and then leak. This leaking water can pool and become a suitable breeding ground for mould and mildew – two of the more common causes of a smelly air conditioner.

A dirty air filter can also cause a musty smell, particularly in regions with high humidity. The excess moisture from your air conditioning unit can settle on the filters and produce unpleasant smells, while dirty filters can also affect air quality.

2. Air Conditioner Creates a Burning Smell

Air conditioners house their fair share of components and circuitry. And like all electrical appliances, there’s room for faults. A burning smell coming from your air conditioner typically suggests that one or more of the electrical components have fried. There are numerous reasons why this might happen, including:

• water damage
• overheating
• a build-up of dust
• many other issues

Scheduling maintenance for your air conditioner can reduce the likelihood of build-up and clogs, so it’s always wise to organise an annual service.

Similarly, a burning smell in the aircon unit could indicate that the fan motor or circuit board has burnt out and needs replacing. Overheating, water damage or the circuits receiving the incorrect voltage can cause this bad air conditioner smell.

3. Air Conditioning Unit Produces a Cold-Like Coolant Smell

An air conditioner producing a cold-like coolant smell can indicate that your system is leaking essential fluids. Refrigerant gas is present in split and ducted reverse-cycle air conditioning systems. The system relies upon this gas to treat the air before it’s dispersed throughout your home.

This odour suggests that the refrigerant is leaking. It has the potential to exacerbate existing health problems while also limiting the performance of your air con.

Only licensed air conditioning technicians are legally permitted to perform an air con regas. So, if you do smell this odour and suspect a refrigerant gas leak, shut down your AC, open the windows and give us a call.

4. AC Smells Like Exhaust Fumes

Air conditioners have motors, and these motors require lubrication to keep functioning at their best. Therefore, oils come into play.

If the oil was to leak, or the central unit was to overheat, that oil could burn and leave your air conditioner smelling like undesirable, indoor air quality-affecting exhaust fumes.

In an insufficiently ventilated home, the exhaust fumes may cause problems beyond just an unpleasant smell. You can run into a plethora of potential health concerns. So, contact your licensed aircon professional and get that issue fixed ASAP.

5. Aircon Produces Rotten Smell

So, we’ve saved the “best” foul smell for last.

Imagine you’re trying to simply enjoy some cool, climate-controlled comfort indoors. Problem is, you find your air conditioner smells like rotten eggs or – dare I say it – rotting flesh. In this instance, there’s a strong chance that an animal or rodent has died in your system. Sorry.

Rats, mice, lizards, birds and possums often explore the compressor or ducts only to get trapped and die. It’s only a matter of days before they start to produce a distinct smell and you’ll find your air conditioner smells terrible.

The good news is that our technicians can address this problem. We can determine whether or not dead animals have affected the performance of your air conditioner and apply the necessary fix.

BONUS: Your Aircon Smells Like Cigarettes

AND a bonus one for good measure … the cigarette smell.

If your air conditioner smells like cigarette smoke,  your system has likely absorbed smoke particles from the surrounding environment. This can happen if someone has lit up near the unit, allowing the coil and air filters to absorb cigarette smoke.

A running air conditioning system circulates these particles, spreading the smell throughout your home. To minimise this bad smell, you’ll need to regularly clean and replace your air filters. In severe cases though, you may need a thorough system clean by a licensed technician.

To prevent this unpleasant odour in the future, try and discourage smoking near your air conditioner.

How To Deal with a Stinky Air Conditioner

So you’ve found yourself dealing with an unpleasant air conditioner stink; possibly any one of the five air conditioner smells described above. Here’s what you need to do to deal with a bad smell from your air conditioner while you wait for a licensed technician.

• Mould and mildew – We recommend cleaning the filters every three months, whether or not your air conditioner smells bad.
• Burning smell – If the smell dissipates quickly, then there may be nothing to worry about. But if the smell sticks around for longer than a few seconds, or the unit produces smoke, you should shut it down immediately and call a licensed technician before further use.
• Coolant smell – A chemical smell, similar to coolant, suggests a refrigerant leak. In this case, turn off the air conditioner, open the windows, and call a professional for an air conditioner regas.
• Exhaust fumes – If your air conditioner smells like exhaust fumes, the unit’s motor may be overheating or oil is burning. This bad smell points to a serious issue, so stop using the system and book a service right away to prevent long-term damage.
• Rotten dead animal smell – Unfortunately, this is something you’ll need a technician to remove. Cleaning the system can help restore indoor air quality and eliminate the odour.

Regular maintenance and prompt attention to unusual smells can prevent these issues from getting worse.

Air Conditioning System Repairs

If you’re experiencing any of the above air conditioning smells, your best course of action is to have a professional inspect the system and recommend the appropriate fix.

Repairs or a thorough clean will hopefully be all that’s required for your air conditioning unit. But if key circuitry has burned out, it might be time to consider replacing the air conditioning system or looking into an upgrade.

Whatever the cause, contact the experts at Metropolitan Air Conditioning. We can schedule an inspection or provide emergency after hours service. Request a repair and improve your indoor air quality today.

Please note: This information is provided for advice purposes only. Regulations differ from state to state, so please consult your local authorities or an industry professional before proceeding with any work. See our Terms & Conditions here.