Why Does My A/C Smell Bad?

Why Does My A/C Smell Bad?

With summer right around the corner, many of you are turning on your air conditioning only to be hit with an incredibly awful smell. Just what is that smell?? The two more common smells our customers face when turning on their A/C are “rotten egg” or “dirty socks.” If you are experiencing either one of these, give us a call so we can take a look.

Let’s start with something simple. Have you checked your Cabin Air Filter lately? They are designed to trap dust, dirt, pollen, spores and germs. If your Cabin Air Filter is dirty, it won’t filter these harmful particles which could be the cause of the smell. Other common smells could be from food stuck in the seat cracks, pet hair, children’s accidents/spills, and smoke. Over time, as you recirculate the same stale air through your Cabin Air Filter, it won’t be as efficient, hence the smell, and you’ll know it’s time to change it. Ron’s Garage recommends replacing the Cabin Air Filter about every 15,000 miles or every year. If you go too long with a dirty filter, it can become so clogged that it restricts air flow significantly, which in turn stresses other components in your A/C system and can shorten their lifespan.

Dirty Cabin Air Filter

Why Does My A/C Stink?

When you turn on the air, the blower motor forces air across your evaporator and out through the vents on your dash, floor, and defroster. As warm air passes over the cold evaporator coils, condensation occurs. The dirt and dust that is present mixes with the condensation and creates the perfect breeding ground for bacteria, mildew and mold.

Why Does My Car Smell Like Dirty Socks?

That musty, dirty sock smell is likely coming from mold, mildew or bacteria that has built up in your A/C system. The mold could be on the evaporator core/coils, the condenser, in the ductwork or even a clogged condensate line.

Things to Watch Out For:

  • Visible mold/mildew build up on your evaporator coils and/or mold growth that has spread from somewhere else
  • Weaker air flow than normal
  • High humidity levels inside the vehicle
  • Leaks or standing water by the condensate drain line
  • A/C shutting off suddenly

What is That Rotten Egg Smell?

I hate to be the bearer of bad news, but if your car reeks of rotten eggs, you could have a pest infestation or a dead animal stuck somewhere in your A/C system. Don’t worry, it happens to the best of us. This might be the issue if you have heard any scurrying noises, noticed any pest droppings/hair, or if the smell is more prevalent the closer you get to your vents. We don’t blame you if you don’t want to investigate.

Let Ron’s Garage check the cause of that awful smell so you don’t have to cover it up with air fresheners any more!


If you’re lucky enough to be reading this without experiencing one of these awful smells, you may want to know how you can prevent it from happening. A good rule of thumb is to allow fresh air to circulate through your A/C system – all you have to do is switch to fresh air instead of recirculated air to help dry out the interior system. Another quick tip would be to run the fan without the A/C on right before you turn off the car. The theory here is that it will allow the system to “dry out” for a couple minutes before turning off the engine. We would also recommend spraying BG Frigi-Fresh through the air intakes under the hood. According to BG Products, “Frigi-Fresh has been formulated to quickly and effectively remove foul, musty odors from automobile air conditioning systems. It will freshen foul-smelling systems by killing odor-producing organisms. Powerful deodorizers in BG Frigi-Fresh keep automobile interiors smelling fresh and clean.”

Either way, if you notice a funky smell coming from your vents when you use the A/C, your best option for taking care of it quickly is to get your vehicle inspected by the professionals. The technicians at Ron’s Garage will track down the cause of the foul smell and you can rest assured that they will take care of the issue to get you back on the road as soon as possible. Give us a call today to schedule your appointment! (734) 662-8379