Maintaining the air conditioning system in your car is a key part of ensuring comfortable and pleasant driving experiences. It’s just as important to take care of the air conditioning inside your home. Air conditioner maintenance is especially important in the summer, when mold and other bacteria thrive in heat and humidity. Unfortunately, if you overload the air conditioning system, it can damage the air conditioning unit and cause an unpleasant smell to spread throughout your home or vehicle. Want to know how to prevent this?

Damaged Air Conditioning = Unpleasant Odors

There are many different types of unpleasant odor that you may notice after damaging the air conditioning unit. The smell of rotten eggs, burning, gas, and other unpleasant odors can cause headaches and dizziness. Additionally, each of these odors indicates a different reason for air conditioner failure.

In this article, you’ll learn what causes each of these unpleasant smells and how to remove them from your air conditioner.

How Does an Air Conditioning Unit Work?

Your air conditioner actually does not produce cold air. What it does is remove humidity and heat from outside air, making the air inside your home cooler. The coils of the air conditioning unit condense the humidity and heat of the air. This process removes moisture before sending the cold air into the home through the air conditioner’s ventilation ducts.

Because this cool breeze is significantly colder than the surrounding air on a hot summer day, the air entering the unit can create humidity that affects the condensing components in the central air conditioner. This process also creates a small stream of water that is drained from the house through the air conditioner’s drain pipe. However, if you have overloaded the air conditioning unit, the moisture may not find its way outside the house through evaporation or proper drainage. This can cause the stream of water to drip into the air conditioning unit surrounding the coils and cause humidity inside the house, resulting in an unpleasant air conditioner smell.

This is just one of the things that can cause an unpleasant air conditioner smell. Below we will discuss more causes.

Five Typical AC Smells. What Causes Unpleasant Smells from the Air Conditioner?

There are many different things that can cause an unpleasant smell to come from the air conditioner. It’s important to immediately find out what the smell is and why it appeared, as it can pose a health threat. Here are some of the most common smells that people often encounter.

Burnt Smell

If your air conditioner smells like electricity or burning, it may suggest that you have a mechanical problem with the fan or compressor of the air conditioner, a problem with the electrical installation, or a failure of the electrical element. Long-term exposure to such a smell is very unhealthy.

To check if this smell is just burning dust or an electrical problem, observe the burning smell for 20 to 30 minutes. If the smell disappears after this time, it was just burning dust. If the electrical smell still persists after 30 minutes, immediately call a professional technician for inspection, who will check the electrical parts of the air conditioner and make the necessary repairs.

Remember that attempting to fix an electrical problem yourself can be very dangerous and ineffective, so it’s better to call an experienced specialist.

Rotten Eggs Smell

The smell of rotten eggs, provided you don’t have any rotten eggs in the house ;), indicates a natural gas leak. Natural gas is odorless in itself, but service providers usually add methyl mercaptan, which alerts people to a dangerous leak with its characteristic smell.

Although low exposure to natural gas is not dangerous to health, high concentrations can lower blood oxygen levels and lead to loss of consciousness and even death. Therefore, it’s important to take certain precautions if you smell gas. First, make sure you have turned off the gas supply. Immediately after this, contact the gas company. Make sure you are not using lighters and matches. Open all windows and doors and leave the house.

If your air conditioner smells like rotten eggs, it could also indicate that a dead animal is stuck in the air conditioning unit.

Mold or Musty Smell

This is one of the most common air conditioner smells. If your air conditioner smells musty, it is most likely caused by water accumulating in the drain pipe and water removal system. Such a problem with the drain pipe can cause the growth of mold and fungi, which result in a musty smell from the air conditioner.

Another cause of a musty smell can be a dirty air filter. This is most typical if you live in a hot and humid climate. If you turn on the air conditioner for a long time, a lot of moisture can accumulate in the filters, which requires changing the air conditioner filter.

You may have heard about the dirty sock syndrome. If your air conditioner smells like dirty socks, it’s because mold is leaking from your air conditioner when you first turn it on. Preventing this syndrome requires calling a heating and cooling company to clean the refrigerant lines and ducts.

Exhaust Smell

If your air conditioner smells like exhaust fumes, it indicates that the air conditioning system in your home has a refrigerant leak. The leak can affect the performance of the air conditioner and also release harmful chemical substances into the environment.

A sweet and chemical smell also indicates a refrigerant leak. The HVAC system of the air conditioner relies on gas to transfer heat through copper coils, which over time can fail. You should also exercise extra caution if you notice the smell of freon and a leak occurs.

When your air conditioner smells bad, like car exhaust, has a freon smell, or a sweet-chemical smell, it is best to call an HVAC repair technician to check the location of the leak.

Cigarette Smoke Smell

If you are a habitual smoker and have a habit of smoking cigarettes in the house or car, you’ll notice that eventually, your air conditioner will start to smell like smoke. Bacteria accumulating in cigarette smoke are usually the cause of this smell, which can cause headaches and allergic reactions due to poor air quality in the room.

The air filter and evaporator coils tend to absorb cigarette fumes. When you turn on the air conditioner, tobacco particles become loose and spread throughout the house or car. You need to clean the evaporator coil and change dirty filters every 30 to 60 days to remove the smell.

How to Clean an Air Conditioner to Get Rid of Unpleasant Smells?

If your central air conditioner smells bad, the best and simplest solution is to clean it. Depending on the type of smell, you should first call a professional to check if there are any leaks or mechanical damages. After everything has been fixed, you can proceed to clean the clogged air conditioning unit.

Step 1: Turn off the air conditioning units

For safety reasons, this should be your first step. If possible, for safety, unplug the power cable.

Step 2: Thoroughly clean the inside of the air conditioning unit

You can start cleaning the inside of the unit when the air conditioner is off. Start by taking out the doors which are on the side of the device; you might need a screwdriver for this.

Next, you can clean the evaporator coils by rubbing them with a soft brush or cloth to get rid of any visible dust.

Then proceed to the next step, removing the drip tray, which should be under the device’s coils. You may even notice some water and mold in it.

If mold is growing in your drip tray, it means that it has stopped working. You should contact a technician to replace it.

To finish this step, clean the evaporator line. You can do this by sucking up whatever may be in it using a wet vacuum cleaner. Your evaporator coils should be located near the air handler.

Step 3: Clean the condensate drain line

The next task is to clean the condensate drain line in your air conditioner. The first step in this process is to insert your finger into the drain line to check for any obstructions that can be removed in this way. The air handler, which is usually located in the garage or attic, should be close to the condensate drain line.

As part of this operation, you should also remove the vent and clean it. This is a vital access point that can become clogged.

A wet/dry vacuum cleaner can be used to remove any obstructions in this area.

After removing all materials with a vacuum cleaner, rinse the condensate line with water to ensure it is empty. You can even use a little vinegar to remove remaining contaminants.

To avoid encountering the same problem in the future, you should use drip tray tablets to prevent the cleansed deposit from returning.

Step 4: Find the air filter and replace it

If you want to get rid of the problem with a smelly air conditioner, the next place to check is the filter. It is usually located next to the thermostat or the air handler.

The fan and motor of your system are inside a large metal box called the air handler. The filter will be inside it.

Your air handler may have instructions on how to insert the filter, so remember to use them.

Once you’ve found the filter, you can start the replacement process.

Step 5: Clean the outdoor unit of the air conditioner

At the start of this process, remove the top of the condensing unit. Once you’ve done that, you can start cleaning.

First, use a vacuum cleaner to remove things like grass, dirt, and leaves. You can also use compressed air to remove contaminants from hard-to-reach places. However, be careful to do this from a certain distance to avoid damaging any internal parts.

A small brush or cloth can be used to remove remaining contaminants.

Step 6: Clean the fans and coils of the air conditioner

For this step, you should use a coil cleaner.

To dilute the cleaner, follow the instructions on the bottle. Apply it to the coils after placing it in your sprayer. In a few minutes, you should notice it starting to foam, and when it does, you can rinse it off.

Make sure you don’t use a pressure washer for this, as it can damage the delicate fins.

Step 7: Spray the unit

Completely spray the unit with water to get rid of any remnants of dirt and dust. You should also rinse the drip tray to get rid of any dust or contaminants that might have accumulated there.

Do not use a pressure washer for this.

Step 8: Final adjustments

Let the unit dry completely. Once you’ve done that, arrange all parts of the air conditioning system in their places.

How to prevent the recurrence of unpleasant smells from the central air conditioner?

Below are tips you should apply to prevent the occurrence of unpleasant smells in your air conditioner.

Clean often

Smells from the air conditioner indicate various things and point to different problems. To effectively improve indoor air quality and get rid of any smell from the air conditioner, you should clean it, and often.


Be consistent in maintaining your HVAC system. Schedule regular inspections to make sure none of the parts of the air conditioning system are damaged.

Invest in an air purifier

An air purifier removes hot/cold spots, reduces dust and allergens, and increases the longevity and efficiency of your HVAC system.