Your car's air conditioning system is relatively similar to the air conditioning systems found in most residential homes, although with smaller components and a few notable differences. Most importantly, most vehicles use variable-speed compressors to alter their output based on your HVAC settings. By contrast, most residential systems operate with a single-stage compressor.
Despite this difference, the basic design is essentially the same. Refrigerant absorbs heat energy through an evaporator coil, and a blower pushes this cooled air through your car's vents. Unfortunately, you may sometimes discover that the cool air coming through your vents has a downright nasty funk. Are these smells harmful, and do they indicate a more serious underlying problem? Keep reading to find out!
Auto AC Smells Demystified
Your car's air conditioner can only pick up nasty odors from a handful of different sources. If you place your HVAC system into recirculating mode, the car will pull air from the cabin and recycle it through the ductwork and filter. The return air will pass through the cabin air filter before traveling over the evaporator coil. That leaves the filter and the coil as the primary sources of odors.
When you disengage recirculating mode, the car will bring fresh air from one or more external ducts. This air will follow the same path as the recirculating air, passing through your cabin filter for cleaning and the evaporator coil for cooling. ]
While your cabin air filter ostensibly helps clean your air, an old or dirty filter can lead to some nasty smells. As dirt and debris build up on the filter, it can become a source of unpleasant smells. However, moisture collecting on the evaporator is often a more likely culprit. Moisture and dirt can create a breeding ground for bacteria and mold, leading to a fairly nasty funk when you turn on your AC.
When to Worry About a Smelly AC
There are a handful of situations where a smelly AC might be nothing to worry about. If you leave your car sitting for a few days, recirculating the air might produce unpleasant odors. Running your AC in fresh air mode should clear out the problem relatively quickly. You might also notice smells if your cabin air filter is very dirty or you frequently switch between AC and heating modes.
However, persistent smells when only using the air conditioner are often warning signs. These smells likely mean that you have a build-up of dirt, moisture, mold, or bacteria on your evaporator coil. Since air must pass over the coils, it will pick up these smells as it goes. Cleaning evaporator coils is often a fairly intensive job, so it's a service best left to professionals.
A build-up of dirt and mold on your coils can also point to an underlying issue with your AC system, such as a clogged condensate drain or a refrigerant pressure issue. Since low refrigerant can cause your evaporator coils to freeze, these problems can lead to excessive moisture build-up. A professional AC shop can investigate these issues, suggest repairs, or rule out more severe problems.
Reach out to an auto shop that offers car air conditioning services for more information.
Share16 May 2023
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