Why Does My Car Air Conditioning Smell Bad?

It’s a common problem to climb into your car and discover that the car smells when the air conditioning is on. Especially if you haven’t used your air conditioning over the winter months, you can be in for a shock on the first hot day of the year.

If your car smells when air conditioning is on it’s usually caused by things like build ups of dust and bacteria, leaks in the system or damp and mouldy components. Tracking down the cause of a bad smell can be a challenge, even for seasoned professionals. In this article we’ll go over some of the main reasons your car’s air conditioning smells bad and what you can do to fix it.


  1. My Air Conditioning Smells Stale

Air conditioning that smells stale, dusty or stuffy is usually caused by a buildup of dust and bacteria in the ductwork under the dashboard. Your car constantly draws in fresh air from the outside, and this air is passed through a cabin filter to remove any dust and dirt. The cabin filter will become clogged over time and dust can start to build up in the ductwork. This dust breeds bacteria, causing your car to smell like an old bag that’s been in storage too long.

So if your car smells when air conditioning is on, the fix for this is easy – simply change your cabin filter for a new one. You can ask your mechanic for help, or your owner’s manual can show you what you need to do.


  1. My Air Conditioning Smells Musty or Mildewy

Musty, mouldy or mildewy smelling air conditioning is usually due to trapped moisture. Typically that moisture gets trapped in the fresh air intake for the cabin, or in the evaporator coil located under the dashboard. The evaporator coil is the piece of the air conditioning system that cools down the air. It’s made up of hundreds of tiny pipes and fins that tend to catch dust which can trap moisture and lead to the growth of germs, mould and bacteria that cause a musty smell.

Because the evaporator is located under your dashboard, cleaning it is a job for a car air conditioning technician. It’s a straightforward process and your technician will use special chemicals to kill off any bacteria and have your car smelling like new again.


  1. My Air Conditioning Smells Sweet and Sickly

A sickly sweet smell coming from your car’s air conditioning may be caused by a coolant leak. Cars use hot coolant from the engine to create heat for the cabin. That means a leak in your heater system can cause coolant to enter your air conditioning ducts and fill your car with a sickly sweet smell.

Repairing or replacing leaking heater components is a job that’s best left to a professional mechanic.


  1. My Air Conditioning Has a Chemical Odour

The air conditioning in your car creates cool air by circulating refrigerant through a sealed system. If your air conditioning has a slightly sweet chemical odour, it can be a sign that your system has a refrigerant leak. This smell may even be noticeable when the air conditioning is off. It’s common for the smell to get worse when you turn the air conditioning on and as you increase the fan speed.

Most modern cars use refrigerants with relatively low toxicity that won’t pose any major risks to your health. EVen still, it’s important to have a refrigerant leak diagnosed and repaired as soon as possible. A professional car air conditioning technician has special equipment that allows them to locate and repair invisible leaks to keep your car running perfectly.


  1. Other Reasons Your Car Air Conditioning Smells Bad

Cars are constantly drawing outside air into the cabin to keep things smelling fresh. That means funny smells might not be coming from your air conditioning system. Instead, they can be caused by other problems with your car such as:

  • Burning engine oil
  • Burning coolant
  • Exhaust leaks
  • Engine oil leaks
  • Fuel leaks
  • Coolant leaks

If your car has noticeable leaks under the bonnet then that may be the cause of the strange smells in the cabin. You’ll need to talk to your mechanic to get the problem diagnosed and repaired.


Talk to the Team at AAEAC if Your Car Smells When the Air Conditioning is On!

Car air conditioning can smell bad for a variety of reasons. From excess moisture and refrigerant leaks to simple build ups of dust, it’s a good idea to have your system looked after by a professional. The Access Auto Electrics team are experts at automotive air conditioning! We work on all types of passenger cars, 4x4s and commercial vehicles, and we have the expertise to diagnose and repair any issues with your air conditioning. Our workshop is based in North Brisbane and we’re happy to help customers from across the region. Contact us online if you’d like to book a service or need some advice about the air conditioning in your car!

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