Why Does My Air Conditioner Smell Like Vinegar? [ 5 Causes & Solutions]

Liz Yang

When the summer kicks in, the air conditioner becomes the lifesaver at home. While it provides us with comfort, it can also cause problems. Your air conditioner may occasionally smell like vinegar, which can be quite unpleasant.

If your AC has a vinegar smell, don’t be too concerned. Mold and bacteria in the air filter, evaporator coil, condensation pan, and drain hose are frequently to blame. If you can get these parts cleaned, the smell will go away.

In this post, I will analyze the causes of the sour smell in the home’s ac and then provide solutions to this problem. Continue reading if you want to get the smell out of your house on your own.

Why does my ac smell like vinegar?

Even though your AC emits a vinegar-like smell, it doesn’t mean that someone has poured vinegar into it.

Instead, the sour smell comes from the mold and bacteria inside your air conditioning system. Some microbes can release a sour smell. 

But why will they grow in your AC? There are 5 possible causes.

1. Dirty air filter

dirty ac air filter

Every time you take out the air filter from your air conditioner, you’ll be surprised by how dirty it is. 

The air filter will accumulate a lot of dirt, dust, and debris over time, including dead skin cells, which could be a food source for mold and bacteria.

When the air goes through the air filter, the smell of vinegar will go along with it and enter your room. 

2. Filthy evaporator coil 

dirty evaporator coil

When the air filter becomes clogged, contaminants in the air settle on the evaporator coil.

Aside from that, condensation will occur on the evaporator coil. The evaporator removes excess moisture from the air because the coil is very cold and can cause the air temperature to drop below the dew point, indicating that the evaporator coil is humid.

Mold and bacteria will grow and thrive on the evaporator coil due to the moisture and organic material, emitting a vinegar-like odor.

3. Clogged drain hose

Stagnant water is another common source of a sour odor. The condensate pan is a component of an air conditioner that frequently accumulates stagnant water.

As you are aware, the removed moisture will condensate and accumulate in the condensate pan. When the drain hose becomes clogged, the water in the pan cannot be expelled outside, allowing bacteria and mold to thrive.

4. Contaminated ductwork

Sometimes, the air before coming into your air conditioning unit already has a vinegar smell. This is because the mold and bacteria have built their colony in the ducts and vents. 

5. Electric Motor Emissions

Under rare circumstances, the electric motor can release ozone. Ozone has a complicated smell, some people think it smells like burnt wires or vinegar.

How Do You Get Sour Smell Out Of An Air Conditioner?

Until now, we’ve figured out what could be causing a vinegar smell in your air conditioner. In this section, we’ll talk about how to fix it.

Most problems, in my experience, can be solved without the assistance of a professional.

Clean the air filter

The main cause of a stinky air conditioner is a dirty filter. Fortunately, it is the simplest internal component of your air conditioner to clean.

Remove it with care and then rinse it under running water. You can remove the debris with a soft brush and kill the mold spores and bacteria with a disinfectant cleaner.

Clean the evaporator coil

Cleaning the evaporator coil is a bit more complicated because you can’t take it out directly. 

To remove the grime and dirt, you can use a vacuum cleaner and then apply some mild detergent to it. After a few minutes, you can use a clean, soft cloth to take away the loosened impurities.

Remove the blockage in the hose

You should unclog the hose to ensure there is no stagnant water in the ac.

Fortunately, you can disassemble it and then remove the buildups with a long brush or something similar.

You can put back the hose once it is completely clean.

Clean the ductwork

If you don’t have the expertise, I suggest you consult an HVAC professional. They will give your HVAC system a deep clean even though it can cost you some money.

Fix or replace the electric motor

Don’t try to fix the motor by yourself. But fixing a motor by a pro can be very pricy. In many cases, replacing it with a new motor is a more sensible idea. 

How to prevent the vinegar smell in your ac from returning?

If you have tried the methods mentioned in the previous section, the vinegar smell should disappear. But how to refrain from it in the future, you should take some measures.

Regular maintenance 

Many of us like to leave the air conditioning system unattended, but that can wreak havoc with time. 

Having it serviced on a regular basis can ensure that there are no obstructions in the air filter, drain tube, or other parts.

Meanwhile, it can make sure the higher efficiency of your machine, saving the electricity cost for you.

Take advantage of a dehumidifier 

The more humid the air, the more water your air conditioner will collect. To reduce the amount of stagnant water in the condensate pan, run a dehumidifier ahead of time to remove excess moisture.

Using a dehumidifier is also an effective way to control mold growth, reducing the mold spores that can get into the ac.

Make use of  an air purifier 

A good air purifier will also filter out bacteria, mold spores, and debris in your home.

If an air purifier is constantly running, your ac air filter will collect fewer impurities. This reduces the likelihood of your ac emitting a vinegar odor.

Final thoughts

Having an air conditioner that blows out the air with a vinegar-like smell is annoying. Luckily, it is easy to handle. 

If you notice a sour odor coming from your air conditioner, it is likely that the filter or drain hose is clogged. The humid environment, combined with the dust and debris, provides an ideal environment for mold and bacteria to grow and thrive, and some of these microbes will emit a vinegar-like odor.

If you want to avoid this problem, you should perform regular maintenance on your air conditioner and consider using a dehumidifier or an air purifier alongside it.

Liz Yang is the founder of Airsmartly. She has been working at home for a few years and realizes that the performance of the HVAC system plays such an important role in our life. She has tested a lot of products in person, like humidifiers, air purifiers, dehumidifiers, and ACs, and wants to share tips about using or troubleshooting these products with you. Her uncle is an HVAC expert with over 30 years of experience in the field, and often offers assistance when she is unsure how to handle a situation. He is also in charge of reviewing the articles on this site.

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