Air Conditioner Smells Bad in Car: Reasons and Solutions

Getting in your car in the morning and discovering that a foul smell is coming out of the AC is never fun. Whether you’re going to work or on a long trip out of town, it’s rare that you’ll have the time to deal with such a problem.

And yet, deal with it you must, especially in some cases, depending on the smell.

So, the air conditioner smells bad in car – what should you do?

Performing an immediate and quick diagnostic is always a must as some of the possible causes of this problem can be quite unfortunate and dangerous. We’ll list the different possible issues “by smell” below but keep in mind that just sniffing the air and concluding “Oh, this smells like X so it’s probably not urgent” is not what we mean by “a quick diagnostic”.

Our sense of smell is highly subjective and people often characterize the same smell as wildly different things. So, whatever your car’s AC smells like, it’s wise to be thorough in your diagnostic. But, to start off, here’s what the different smells typically mean.

My car air conditioner smells like gas

This is a simple one – if your car’s air conditioner smells like gas then you almost certainly have a gas leak on your hands. The reason you smell it when the AC is on is that the gas smell gets sucked into the fresh air the AC is taking.

Naturally, if there is a gas leak you need to get it under control as soon as possible. There are several possible areas in your car a gas leak can be coming from and you’ll have to check all of them.

  • First, inspect the fuel pressure regulator to see if the leak is coming from there.
  • Then, look at the fuel injector’s “O” rings in the engine compartment.
  • Last, look at the exhaust pipes and the exhaust muffler for any holes.

Even if you find a gas leak in one of these places, check the other two as well – having more than one gas leak is entirely possible.

My car air conditioner smells like chemicals

If you’re sensing a weird chemical smell coming out of your car’s AC then that’s probably the car’s refrigerant/antifreeze. To many people, this also feels like a “sweet” smell, as if someone has dropped a piece of candy on the engine. The reason for this is that the toxic liquid ethylene glycol can have a sweet smell to it.

This type of leak can come from either one of several possible locations as well:

  • The coolant housing unit
  • The radiator
  • The heater core
  • Any pipe or hose

So, there are quite a lot of places you’ll have to check but you do have to check all of them as ethylene glycol is quite toxic.

My car air conditioner smells like vinegar

One of the more common smells people sense is that of vinegar. It can also feel like food or, more disturbingly, what if your car air conditioner smells like urine? How about wet socks?

All of these smells are usually due to mold or mildew building up in your car. The reason it feels different can be because of how much mold there is, exactly where it is, how you perceive the smell or what type of mold we’re talking about. There are actually thousands of types of mold, some more dangerous than others.

Whatever type of mold you’re dealing with, it’s wise to get rid of it as soon as possible. Even if the mold in your car is not too dangerous for your and your family’s respiratory health, it’s still eating through the soft parts of your car’s ventilation system. So, once again, you’ll have to check several different spots:

  • Your car’s AC evaporator, right behind the dash panel
  • One or more of the AC’s drain holes
  • The air filters of your car’s AC can also accumulate mold

Fortunately, mold is one of the easier problems to fix as you usually won’t have to replace any damaged components. Just turn on the AC, open all its vents, turn the fan to the highest possible setting, turn off the recirculation (so that the AC draws air from the outside), open up the car’s windows, and then spray Lysol or any other good disinfectant in the air intake vent (usually on the outside of your vehicle and at the bottom of the windshield).

Just spray the whole can of disinfectant into the suction vents as the AC is running – make sure to put some in all intake vents on both the drivers’ and passenger’s sides. Then, just leave the vehicle running for ~10 minutes.

My car air conditioner smells like burning plastic

If you’re sensing a smell of burning plastic or burning rubber, this usually indicates that something is unfortunately been irreparably burned off. This could be a fan, some electrical wiring, the driving belt, a worn-down clutch (especially if the smell intensifies when you’re switching gears), and other such problems.

If any of this is the case, you need to go to a professional car inspection as soon as possible as either of those things can cause a serious accident.

Fortunately, there can be some less problematic causes for such smells – a burning plastic bag somewhere in your car’s inner-workings, an antifreeze leak, or just the heater burning off some dust that’s accumulated on top of it. In other words, this smell can either have some very serious or some rather insignificant causes. Either way, it merits immediate and thorough inspection.

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