Car Odors from the HVAC

Car Odors from the HVAC

When you turn on your car’s HVAC, you expect some cozy warm air in the winter and a refreshing blast of cool air in the summer. If, instead, the car is filled with a foul odor, you’re totally baffled. You don’t smoke. You don’t allow smoking in your car. No fast food wrappers on the floor. No old gym clothes on the back seat. Rover was a good boy last time he was in the car.  What could it be? Here are a few of the “suspects.”


If the smell is kind of stale, kind of musty, kind of moldy, mildew is growing in the HVAC system. It’s a fairly common situation. There are a few places susceptible to mildew.

  • Your car’s climate control system, particularly in the evaporator core and near your a/c unit’s condenser. Mildew thrives in moist, enclosed places.
  • The heater box when it remains damp instead of drying out. Heater boxes typically have pipes that allow the condensation to drain out. Like when you see water under your parked car if you’ve been using the a/c, it came from the heater box. If something has interfered with the heater box draining properly, water collects in it and, ta-dum, you have mildew.


The smell of antifreeze can come out of your HVAC system, but it isn’t offensive to everyone. It smells like maple syrup to some people. But to others, it’s a sickening sweet smell and a trigger for a headache. If you have antifreeze leaking into the heater box, the smell will spread throughout your car.


Hydrogen sulfide smells like rotten eggs. Catalytic converters alter exhaust gasses to reduce harmful emissions into our environment. When your converter goes haywire, it can alter the gasses so that they become hydrogen sulfide. That odor can also come from old lubricants used in manual transmissions.


While you’re driving, dust is collecting inside the car’s vents, and it isn’t merely the kind of dirt that swirls up from the road as the car passes by. It can contain pet dander, flakes of skin and other forms of biological waste that create an odor that’s going to come into your car through the vents.


All rodents need is an opening the size of a dime to be able to slip into your car. They may be nesting in the heater box or packed into the blower motor. They don’t smell real lovely under the best of circumstances, but if they’re living there, they are, naturally, doing their business, and their “business” is in the fresh air intake, heater box and/or the air ducts.

Worse yet, you may have the odor of a dead creature coming through those vents. Either a rodent has passed away while visiting your car or a larger animal, such as a cat, has sought warmth or refuge in the undercarriage. You turn on the motor, and the cat is in the wrong place at the wrong time. The fur flies and . . . we don’t really need to get more graphic, do we?


Skunk gets its own category, not because its odor is “singular,” but because a skunk doesn’t take up residence in your car. You would have to hit a skunk for it, or parts of it, to get into the undercarriage  and vents. You have the stench of a dead animal, and compounding that, the skunk’s musk settles into the plastic, and it’s going to be there any time you crank up the heat. And you don’t even have to hit and kill the skunk. All you need to do is drive through the musk and it’s in your air vents.

No matter if you find your “guest” and shoo off the living or dispose of the body of the deceased, the odor lingers on. It could take a couple weeks. It could take a month or more. Are you prepared to drive around with the odor blowing on you, on your clothes, sinking into upholstery and carpet?

To rid your car of all odors, call The Odor Guys at 207-839-9111. We have the equipment and the experience to remove all odors from your vehicle.

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