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8 Causes of the Odor Coming From Your Air Conditioner

Happy Male Technician Repairing Air Conditioner With Screwdriver

Imagine coming home from a long day at work. You lie down on your bed, stretch your legs and turn on the AC to get more comfortable but what is that?

A strange stench is waiting for you, making you anxious and worried about your AC performance.

There are several reasons why your AC can emit an odor; some causes are much more severe that require an HVAC specialist’s help. At the same time, others are pretty common and can be solved with DIY.


The most common causes of getting a smell from your AC unit the moment you turn it on can be

  • Clogged Filters
  • Blocked drain pipe
  • Dirty drain pan

Are you sick and tired of having a smelly odor in your room? Read further as we explain 8 reasons why your AC smells terrible and its easy fixes.

8 Causes of Odor Coming From Your AC

Air conditioners are one of the most convenient appliances that ever existed. They keep us comfortable by regulating a moderate temperature irrespective of the outside one.

Here are a few common reasons if you are experiencing an odor from your AC:

1. Leak in Refrigerant Line

Air Condition Unit Refrigerant Fluid Leaking With With White Fome Freon Chemical, Preventive Maintenance Need To Checkup Annually.

A refrigerant is a cooling agent inside your AC that extracts the heat from the air and helps regulate your room’s desired temperature.

If you notice a running car exhaust-like smell coming from your AC, it is due to the leak in the refrigerant line that will hinder the appliance’s performance along with an uncomfortable stench.

Moreover, it releases hazardous chemicals called Feron into the air that can affect the air quality and safety of people in your home.

Feron is heavier than air, and if it is present in your home, after a while, it will come down, affecting your room’s air quality.


  • Never take this smell lightly, and always pay close attention to address this problem as soon as possible.
  • Immediately call an HVAC specialist to get the refrigerant line fixed. In the meantime, open your home windows to prevent any hazardous impact from the gas leak.

2. Lack of Maintenance

Many Dirty Dust Part Filter Of Old White Air Conditioner Element Technology On Wall In Home Room

Air conditioners need regular maintenance to perform well and be in their best condition. You can get a burning-like smell if you turn on your AC after a while.

It is due to the dust that settles in the unit that burns once your turn it on. Although this smell is temporary and goes away within a few minutes, it is better to keep your AC clean to avoid it.


  • A thorough maintenance of your AC by an HVAC expert is highly advisable to keep it clean.
  • Moreover, it will also help you know about the condition of the internal parts of your device and get things repaired or replaced accordingly.

3. Short Circuit

Burning Switchboard From Overload Or Short Circuit On Wall Close-Up. Circuit Breakers On Fire From Overheating Due To Poor Connection Or Poor Quality Wires. Faulty Home Wiring Concept

Your AC comprises several internal parts that help it do its job effectively.

If you notice a constant burning smell the moment your turn on your AC, it can be due to any internal component burning or melting.


Immediately turn off your AC and call a professional for help. Never try to fix things yourself or use the appliance, even after getting a burning smell, as it can cause further damage to it.


Never try to DIY the AC repair to save some bucks. Always call a professional for help, as you can damage the internal components of your appliance.

4. Clogged Air Filters

Woman Hand Holding Dirty Home Air Conditioner Filter For Remove For Cleaning Air Conditioner.

Air filters are an essential part of your air conditioner. They keep purifying the air coming into the room by accumulating dust, hair, and other particles.

Over time, the filters clog and start storing more moisture resulting in mold growth.

If you notice a musty smell from your AC, it can be due to clogged filters that need your attention.


Cleaning the air filters is relatively easy and does not require professional help.

  • You need to open the front panel of your appliance and take out the air filters.
  • Thoroughly wash them with warm water to clear out dust and debris.
  • Please do not use any detergent in cleaning, as it can damage the filter.
  • Let them dry in a shady place to avoid direct sunlight.
  • Place them back and feel a remarkable increase in your AC performance and no pungent smell.

5. A Critter Stuck Inside

View Of Set Up And Clean Conditioner Coarse Filter. Dirty Filter.

If your notice a foul egg-like smell coming from your AC, it can be due to a critter stuck inside your appliance.

Birds and insects often take refuge in the AC ductwork and get trapped inside the equipment. With time, these dead animals emit a foul smell that can get unbearable.


The best thing is to keep your unit pest-proof to avoid such uncomfortable situations. If by chance, you feel a dead animal is inside your appliance, it is better to call a professional and seek help.

You can also do it yourself by following some easy steps:

  • Open the front panel and try to locate the exact place emitting the foul smell.
  • Look for the dead animal, carefully remove it and clean the area.
  • Check the ductwork and seal any entry points to prevent animals from crawling it.

6. Gas Leakage

Hvac A/C Charging Hose, Cables For Air Conditioning Refrigerant. R134A R12 R22 Cable Refrigeration Charging To Manifold Dual Gauge. Tools For Filling Refrigerant To Air Conditioner. - Selective Focus.

The gas leakage smell from your AC is the most alarming one. If you experience it, immediately turn off your AC, as it can cause severe damage.

Natural gas is odorless, but Methyl Mercaptan is added to make it smell not good. It helps point out a gas leakage and fix it before any hazardous outcome.


As mentioned earlier, in case of gas leakage, immediately turn off your AC and call a professional to detect the source of the leaking and solve the problem.

7. Dirty Drain Pan

Plastic Drain Pipe Of Air Conditioner.

The drain pan is located right under the air filters, and it collects drops of water formed due to condensation and later drains them through a drain pipe.

Another cause of getting a foul odor can be a dirty drain pan. If it has dust particles, immediately clean it to avoid a stench.

The dust particles in the pan mix with water and forms a muggy debris that sticks to the internal AC components, hindering the condensation and resulting in an unpleasant smell.


  • Use a soft cloth to clean the drain pan and mild detergent to eliminate the odor-causing bacteria.
  • Check the drain pan by pouring a small amount of water over it; if it flows nicely to the drain pipe, you have done your job well.

8. Blocked Drain Pipe

Air Compressor Or Air Condenser Unit Located On Support Outside Building To Heat Released Transferred To Surrounding Environment, Compressor Is Part Of Cooling Function And Air Conditioning Hvac Syste

Even if you have thoroughly cleaned your drain pan, often the water won’t go through the drain pipes due to blockage.

If the water accumulates longer in the drain pan, mold and mildew can start forming, resulting in an unpleasant smell.


  • If you notice a clogged pipe, instantly call an HVAC expert for help. They use a process of mechanical suction to clean the pipe without damaging it.
  • Never try to do it yourself by pouring chemical drain cleaners, as it can damage the pipe and cause more trouble.


Getting a foul smell from your unit can be uncomfortable and unpleasant. It is advisable to find the root cause as soon as possible and fix it.

Delaying the repair or using your AC, irrespective of the smell, can cause severe damage to your appliance.

It is better to regularly maintain your AC to know about internal defects and solutions.

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