Smell coming from A/C vents

There is an odor in my car that comes in through the vents of the A/C system. There has been a leaking radiator, but it was replaced. That ‘had’ been a source of one odor, but now there is a 2nd one and it is literally giving me headaches. At times, the smell is rather metallic and like hot exhaust fumes. Yet, it also smells like hot fluid similar to power steering fluid or anti-freeze. The dealer did a pressure-check on the cooling system and reported to me that it is not a heater core leak. I replaced the fresh air filters. Around the filters, I thought there was a gap and leak, but they
Experienced mechanics share their insights in answering this question :
It sounds like you have a leaking heater core inside the evaporator housing and would need to have it replaced. If you have the heater bypassed then you will not have heat inside the car and the temperature control will only work in the cold settings. I recommend having the heater core replaced. You can have this issue verified by a qualified mechanic, such as one from YourMechanic, in order to diagnose the car’s smell and let you know what should be done.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Dirty Air Vents: The unpleasant smells coming from the heating system of your BMW could be a result of dirty air vents. Your car`s air vents get dirty from the accumulation of dirt, pine needles, dust, and debris.
As your vehicle ages, bacteria can grow in the system where moisture typically collects — particularly on the A/C`s evaporator. When this happens, a pungent, mildew-like smell can get blasted into your cabin through your A/C vents.
Dusty and Dirty

Air filters collect dust mites, dirt, and pollutants, the buildup of which can cause an unpleasant smell from your vents when you use the AC or the heater. This putrid smell can be avoided by replacing air filters every 10,000 to 15,000 miles as recommended by the vehicle manufacturer.

The primary cause of a bad air conditioner smell is infrequent system cleaning. Dirty internal parts can be home to mould and mildew, which will inevitably breed bacteria and other things you don`t want in your home. It`s essential to have your air conditioning system routinely serviced and cleaned.
Usually, when you smell coolant from the vents, it`s caused by a coolant leak near the heater core. It could be the core itself, a coolant hose or a hose connection that has split. You should probably have a professional mechanic locate the source of the leak sooner than later, as this could lead to overheating issues.
You can place a dish of baking soda or even the whole box in your air ducts. Baking soda will help to absorb foul odors; however, be sure that your HVAC filter is clean before doing this.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Soap smell coming out of car after cabin change. Changed filter the the smell is still coming. What to do about this strong smell?
ANSWER : Hi There,
As you know, your car has a cabin filter that serves to filter the air that is introduced to the cabin inside the vehicle. The best way to remove your cars interior ac odor is to use a cleaner that uses enzymes. Enzymes in cleaners kill odors at the source and completely kill the smelly substance material and therefore stopping the a bad smell. To get rid of the smell, try the following: First turn on the ac to full, make sure the “recirculate” button is not on, spray a large amount of cleaner with odor killing enzymes into the EXTERIOR air intakes that are located just below the windshield wipers, let the car run for about 10 minutes with the ac on, after 10 minutes turn off ac and spray the cleaner into the ac vents on the INSIDE of your car. After doing all this, let the car sit for 20 minutes turned off and windows rolled up. Then repeat if the smell is still in the car. By doing this you are killing the bacteria or mold in the car ac vent ducts and also the evaporator mold that may be present.

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Sour, stale smell coming from air vents
ANSWER : This is most likely a cabin filter that needs to be changed. Your car is equipped with an air filtration system that works similarly to your engine’s air filter in that it filters the outside air as it flows into the cabin of the car when you have the vents open. Over time this filter will get dirty just as your engine air filter does and, in some cases as you describe, it will emit an odor or smell that is filtered into the cabin when you turn on the vent air.

I would recommend having an expert mechanic, such as one from YourMechanic, come to your location to replace the cabin air filter for you.

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Weird smell coming thru a vents
ANSWER : White smoke through the vents can indicate a leaking heater core. Coolant circulates through the heater core which is behind the dash to provide heat. If no coolant leaks are obvious under hood, the heater core may be your culprit. I suggest having the cooling system pressure tested by one of our mobile technicians to locate the coolant leak for an accurate repair.

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Black soot and bad smell coming from the heater vents.
ANSWER : Hi there. Sounds like the cabin air filter to the heating and a/c system is degrading and peeling apart. The stuff that is coming out into the cabin area is a filter full of dirt and debris. I recommend replacing the cabin air filter and the black sooty stuff will stop coming out. Old filters will make a bad odor in the cabin area, especially when the filter gets heated up.

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My 2016 Toyota Camry had a stagnant water smell coming through the air vents. I asked the service center Not to use any fragrances
ANSWER : This is something I always do in place of perfumed disinfectants. My other half is also sensitive to perfumed sprays. I use a name brand household spray disinfectant. They are available in different scents that you may be less sensitive to. I repeat this process a couple of times per year, or whenever it starts becoming a problem. First, turn the a/c on Recirc with the fan on medium to high speed. Spray the disinfectant down near the floor under the dash on the passenger side. When you set the system into Recirc, the air is drawn in from the heater ducts. Spraying down under the dash gets it pulled up into the a/c evaporator. I do that a few times. Then move the temperature selector to Hot and repeat. Once you’ve done that, switch off the Recirc feature and open the hood. Fresh air for the heat and a/c system is generally drawn in near the passenger side at the base of the windshield. You may even see some sort of grille in that area. With the fan still set on High, spray some more disinfectant in that area so it gets drawn in with the fresh air. Do that a few times then switch the temperature selector back to cold air and a/c on and spray some more. Once you’re done, allow the car to run with the a/c on, the fan on high speed, and the windows open for 5-10 minutes.

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I started my car this morning and as I started down the road there was smoke coming out if the vents. The smell was like a wood fi
ANSWER : There are a few different things going on with your 1994 Chevrolet Cavalier. If smoke is coming from the vents the most likely cause is an electrical fire either inside the vehicle or from the engine bay, or smoke from burning oil in the engine bay. In either case the vehicle should not be driven and the root cause can be determined. Electrical fires can be caused by hidden wires rubbing together over time until the short and can be difficult to detect. A qualified Technician such as one from YourMechanic will be able to diagnose your electronic issue and ensure that your vehicle does not start smoking again.

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Plastic burn smell when opening driver door. Cannot smell inside cabin. Oil full, brakes ok.
ANSWER : Hi there. It is very difficult to "guess" as to the cause of a smell like you’ve described without being their to inspection the car personally. I would highly recommend having a professional mechanic complete a smell in the car inspection; especially if you believe it to be an electrical short.

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Bad smell coming out of the air vents when running air
ANSWER : Hi there, thanks for writing in. I’d be happy to help. This is often a common issue with a bad cabin filter. This is a paper element that works similarly to an air filter for your engine, but filters the air that comes into the car’s cabin. When this is dirty or has picked up something into one of the car vents, this can emit an odor into the cab. I would recommend having this changed at your next service as it will not harm the car in any way.

Here at YourMechanic, we can have a technician come to your home or office to perform your next oil and filter service for you.

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