Air Conditioner Smells [Proven Solutions]

An air conditioner does not have a smell, whether or not it is operating. But if an air conditioner smells, it may be because of dirt or a lack of maintenance. Learn more in this article.

Air Conditioner Smells Bad When Turned On – What to Do

If you turn on your air conditioner and it smells terrible, you may have a dirty air filter or evaporator coil. The smell may also stem from the drain line, drain pan, or ductwork. Let us explain.

1. Air FIlter

The primary duty of an air filter in an air conditioner is to remove pollutants from the air and leave it cleaner. Therefore, replacing the filter every two to three months is crucial. If left in the air conditioner for too long, it may grow mold or mildew, which is highly likely due to possible moisture. Over time, the filter pollutes the air and releases a bad smell. The best solution is to replace the filter if it is old or wash it if it is still reusable.

2. Evaporator Coil

The coil is also in danger of mold or mildew if excess moisture is on it. Typically, the evaporator coil is where the refrigerant absorbs the heat from the room air and returns it cold. As a result, the coil is usually cold, although it does not freeze. 

However, if condensation regularly builds on it and mixes with dirt, it creates an excellent breeding ground for bacteria. You will find the evaporator coil in the indoor unit; consult the user manual for the exact location of the coil in your specific brand. Clean it using a soft brush and soapy water.

3. Drain Line

A clogged and dirty drain is the most probable reason for a smelly air conditioner. It is through the drain line that condensate from the air conditioner flows out of the air conditioning unit. But over time and with constant use, dirt and debris may clog the pipe. 

While it slows the water flow from the unit, it also allows algae, mildew, and mold to grow, encouraging foul smells. Pour a mixture of vinegar and water into the drain line to push the dirt out and sanitize the line. Bleach can also work in the place of vinegar. It should clean out the line and stop the smell if it originates from there.

4. Drain Pan

However, if the drain line is the source of the smell, it may stem from the drain pan. When the excess condensate flows out of the air conditioner, it enters the drain pan and flows through the drain line. If the pan has standing water for a long time, it becomes stagnant and smells over time.

Cleaning the drain line should get the water flowing out of the pan. But you must clean and sanitize the pan afterward with bleach and water. Wash it with mild soap and warm water and sanitize it to make it unconducive for microorganisms.

5. Ductwork

The ductwork is a closed system through which air flows in the air conditioning system. If it is compromised and leaks, it opens the door for air loss and pollutants to enter. These pollutants cause the growth of mildew and mold, which eventually cause bad smells from the air conditioner.

You can try patching the leaky spots on the ductwork if you can reach it and have the skill set. But it is usually better to get the help of a professional HVAC technician or the original installers to check the ductwork for leaks and patch it.

6. Inactivity

During the cold months, air conditioner owners tend to use the appliance less. Some do not use it, especially if they travel during those months. Such people cover the air conditioners for long periods, and when they want to use them again, there may be a bad smell.

This is typical and may be nothing more than the musty smell that comes with an unused air conditioner, primarily because of moisture. Running the system for a few hours usually eliminates the odor, but you may consider cleaning it before a prolonged use if it smells too much. 

Replace the filter, clean and sanitize the drain line and pan, and clean the coils. It may be best to employ the services of an HVAC professional because the air conditioner may need extensive attention and servicing after a long period of non-usage.

Air Conditioner Smells Musty – Fixed

Several faults can cause an air conditioner to smell musty or damp: too much moisture on the evaporator coil or in the ductwork and a full drain pan. Also, the drain line may be clogged with debris, or the air conditioner may be too big for the room size.

1. Evaporator Coil

Ensure the air filter is clean; a dirty air filter can blanket the evaporator coil with dirt and cause freezing. Replace or wash the filter if necessary. If the coil is dirty, the dirt restricts airflow and causes condensation to build, which freezes and increases moisture. 

This creates a breeding ground for microorganisms, leading to a musty smell. You can also clean the coil after removing the old filter and putting in a new one to improve airflow.

2. Ductwork

If there is high humidity in an area, there will be too much moisture in the ducts or the vents. The same is true if there is a leak in the drainage system. The ductwork may grow mold and mildew if your air conditioner smells musty when in use. 

Accessing the ductwork may be difficult because it may be located in a crawlspace or inside the ceiling. Moreover, a trained eye should check the mold growth to know how extensive it is. Mold is dangerous to human health; it can cause issues with the respiratory system.

3. Drain Pan

A musty smell can come from a dirty drain pan. The same is true if there is standing water in the pan. With dirt or stagnant water comes mold, which creates a musty or foul smell. You can always wash the pan with warm water and vinegar or bleach and water to sanitize it and remove the smell. It is also crucial to clean the pan regularly, especially when the weather is humid.

4. Drain Line

Like the drain pan, the drain line may become clogged with dirt and prevent the free flow of water from the air conditioner. And if that happens, it causes the drain to smell. It becomes a health hazard if the drain line remains clogged and water stands in the drain pan; bacteria and other microorganisms can grow in damp and dark places.

5. Air Conditioner Size

If your home’s air conditioner is too big, the unit will cycle too quickly and turn off. As a result, it may not have enough time to dehumidify the house, leading to a buildup of excess moisture. The moisture is stored in the air conditioner and causes issues with the evaporator coil and drainage system. You may have to trade the current unit in for one more suited to the size of the house for better results.

Air Conditioner Smells Like Fish – Quick Fix

If your air conditioner smells like there is fish stored in it whenever you turn it on, the cause may be fungal growth. Mildew and mold create different odors depending on the area and condition of the air conditioner. 

Cooling systems make excellent breeding grounds for fungi and other microorganisms due to dampness and darkness. So, check the air filter, ductwork, evaporator coil, drain pan, and other places likely to be affected by moisture and form a conducive environment for mold.

Another possible source of the fish smell is the plastic components of the air conditioning system. If they become too hot to the point of melting, they give off this odor. Overheating is not a normal part of an air conditioner’s operation, so you may want to check the condition of the condenser coil and fan. But before doing that, turn off the air conditioner to prevent a possible fire. Also, call for professional HVAC help for further troubleshooting.

Air Conditioner Smells Like Feet – Solved

Your air conditioner is dirty and needs a thorough cleaning if it smells like feet. There may be stagnant water in it; over time, algae may grow in it, giving off a foul odor. You can opt to clean the air conditioner yourself, especially the drain pan and drain line, if you have the skill set and want to save money. Check out this article on how to clean an air conditioner drain line for further instructions.

However, a professional technician may be in the best position to do a more detailed cleaning to remove mold and other contaminants. In addition, replace the air filter if you have not changed it in more than two months.

Air Conditioner Smells Like Burning Plastic – How to Fix

There are several faults that can cause an air conditioner to smell like burning plastic. The most apparent reason is one or more plastic parts burning due to overheating. When the air conditioner cannot transfer heat out of the system, it causes the condenser coil and compressor to overheat. 

The heat affects different parts of the system, which may melt some plastic ones. The best step is to turn off the air conditioner if you get a burning smell while it operates. If you continue using the unit while it is burning, there is a fire risk. Then, call for professional help; contact the manufacturer, or hire an independent technician.

Other causes of a burning plastic smell are:

1. Dust

If you live in an area where dust quickly accumulates in homes, you may have an issue with dust in the air conditioner. The smell may come from the heat in the air conditioner burning off accumulated dust and should stop within a short period. 

However, you are more likely to get the smell if the air conditioner is set to heat. If it is set to cool and the unit smells like burning plastic, disconnect it from electric power and get professional help.

2. Damaged Fan Belt

Some air conditioners have a rubber belt driving the condenser fan. The belt is usually strong but weakens with continuous use and eventually breaks. And when this happens, the constant running of the fan motor leads to overheating and melting of the belt. Eventually, you get a burning plastic smell. Disconnect the air conditioner from electric power if you suspect that is the case and get professional help to replace the belt.

3. Electrical Fault

If the wires overheat and begin to burn, they melt the plastic coating to cause a burning plastic smell. The air conditioner will likely develop this type of fault if there is a recent power surge or lightning. 

The same is true if the voltage demands from the air conditioner and other appliances become too much for the current house wiring. Hire an HVAC technician or electrician to determine whether or not there are electrical faults and fix them.

4. Faulty Fan Motor

Check the indoor fan motor if you get an overwhelming burning plastic smell from your air conditioner when you turn it on. The bearings may be worn; if that is the case, the motor may overheat and produce the smell. 

While it may alarm you, it is nothing that a little penetrating oil cannot fix. Also, consider replacing the motor because you cannot fix worn bearings, preventing the motor from fully functioning. You can replace the motor yourself or have a technician do the job.

5. Damaged Capacitor

A capacitor stores power to help the fan motor run when necessary. Therefore, it is a crucial part of the cooling process. However, it may become faulty with years of usage, which may cause the motor to work with a strain. Running and starting by itself will eventually wear the motor out and cause overheating.

Only a trained HVAC technician should test the capacitor because it needs to be discharged first before testing. And discharging the electric power in it is usually dangerous for untrained hands. So, hire a professional technician or have them guide you on what to do.

6. Dirty FIlter

A restriction on airflow from the air conditioner can put a strain on the moving parts. And if this happens, the motors can overwork themselves to provide cool air, leading to overheating. 

The excessive heat can cause a burning smell if it affects plastic parts near the motors. Check the air filter in the air conditioner; clean it if it is the reusable type and is not older than two months. But replace the filter if it is the disposable type and is due for a replacement.

7. Air Recirculation

There may be a fire somewhere else, whether within the house or outside, and the air conditioner spreads the smoke from the fire. You may want to inspect other appliances to ensure none is damaged and pose a fire risk. 

Also, check the vicinity for fires and alert the necessary authorities for proper inspection. The best step is to disconnect power from the appliances until you are sure there is no danger within the house.

Air Conditioner Smells Like Gas – What to Do

If your air conditioner smells like gas, it probably has a gas leak. It may smell like acetone, chemicals like a paint thinner, skunk, or antifreeze. It is crucial that you do not take any chance; disconnect the unit from electric power and contact an HVAC technician for immediate assistance. Ensure you open windows for proper cross ventilation while you wait for help.

While running a gas leak test yourself is not recommended, there are a few simple steps that can tell you whether or not the gas smell comes from the air conditioner. Follow the instructions in this guide to troubleshoot and detect a gas leak if the nearest technician does not arrive quickly.

Air Conditioner Smells Like Rotten Eggs – Quick Fix

There may be a gas leak in the air conditioner. Refrigerant may give off a foul odor, such as smelling like a skunk or rotten eggs. If you smell it, especially when the air conditioner operates, turn it off and disconnect it from power. Open doors and windows, contact the gas company and hire an HVAC technician for further assistance.

It is also possible there is a dead rodent inside the ductwork. An air conditioning ductwork is an excellent hiding place for small animals, especially if there is an opening through which they enter. Let a technician take a look if it is more convenient. But if you can, check the ductwork and remove the dead and decaying animal causing the smell if it applies.

Air Conditioner Smells Like Urine – Fixed

The best solution to a urine smell coming from an air conditioner is to do a thorough cleaning. The air filter is most likely dirty or may have never been changed. As it accumulates dirt and moisture, it becomes a breeding ground for bacteria and fungi, including bacteria that emit ammonia. Ammonia smells like urine, so it may be the problem in this case. Some refer to it as smelling like cat pee.

Clean the filter if it is not due for a replacement and is the reusable type. Otherwise, dispose of it and get a new filter compatible with your air conditioning system. The air filter may have mold, and the mycotoxins it creates can give off the smell of urine or ammonia. If there is mold, throw the filter out even if it is still usable, and replace it.

Also, clean the drain line and pan, and other parts of the air conditioning unit. Check the ductwork for pests that can cause a urine smell, whether dead or alive. Ensure you check and clean the air conditioner every three months to prevent the growth of mold and mildew, which are dangerous to health. Regular maintenance also keeps the unit in top condition.

Air Conditioner Smells Like Cigarette Smoke – Solution

Replacing the air filter and cleaning the coil usually remove the smell of cigarette smoke from an air conditioner. If you smoke heavily, it explains why the smell comes from the unit, but it is unlikely that you will notice the smell because you are used to it. Only a non-smoker will notice a marked difference in the air quality.

An air filter can remove impurities from the air and make it cleaner, but it can only do so much. Heavy cigarette smoke eventually clings to the filter and coil and pollutes the air. Over time, the air from the system smells like smoke. Clean the evaporator and condenser coils but pay more attention to the evaporator because it absorbs heat and odor from the air.

It may be difficult to remove the smell of cigarette smoke completely from an air conditioning unit. Therefore, it may leave an unpleasant air in the house the more you use it. Let a technician do a thorough cleaning job of the unit and see if the smell improves. If it remains, the only other solution is to replace the entire system, which may be ideal if you are sensitive to cigarette smoke.

Air Conditioner Smells After Cleaning – Solved

There may be a mold infestation or untouched places in the air conditioner, causing it to smell after cleaning. Check the ductwork if you notice a smell coming from an air conditioner after cleaning it. 

There may be a dead animal or mold growth, especially if the ductwork leaks. Ensure you replace the air filter if you are trying to eliminate a foul smell and clean the evaporator. Since it can absorb odors, you must thoroughly clean the coil with the proper cleaning agent. 

Remember to remove, clean, and sanitize the drain pan because it can cause a foul smell without proper cleaning. You may have to repeat the cleaning process more often to eliminate the odor. This is especially true if the unit has not been cleaned in a long time. Get professional assistance if the smell remains after a thorough cleaning.

Air Conditioner Smells Bad When Turned On in Car

There may be mold or mildew growth in your car’s air conditioner. The older the car is, the more likely there is to be a growth of fungi. This is especially true if the air conditioner is not regularly cleaned or is not regularly used. Humid days can cause mold growth and encourage fungi in the system. And running the air conditioner at its coldest temperature point causes condensation to build within it.

It is best to take the car to an auto mechanic to check the air conditioner and clean it. The drain tube needs to be removed and thoroughly cleaned. If it is leaking, the mechanic can replace it. An antibacterial cleaning agent can kill any growing microorganisms behind the dashboard. The coils must also be cleaned, and it helps to use only the fan for a while to allow the cleaning agent to work and dry the coils.

Air Conditioner Smells Bad When Turned Off – Quick Fix

Check the drain pan and drain pipe if you smell a bad odor whenever you turn off an air conditioner. The air from the unit may be preventing you from smelling the odor during regular operation, but once you turn the unit off, the stagnant water and possible mold growth begin to smell. 

In addition, check the air filter and replace it if there is mold on it. You should replace the filter every three months. Use professional services to clean the drain, filter, and coils if you are too busy or the task seems tedious.

Air Conditioner Smells Musty After Rain – What to Do

There may be mold or mildew growth in the air conditioner, which becomes apparent after rain. The best solution is to clean the air conditioner coils and inspect the ductwork; it may have holes that let in water during rainfall. Hire a technician to check the unit and do the necessary repairs. Replace the air filter if it is old or has mold growth on it; do not clean the filter for reuse.

Air Conditioner Fan Smells – Quick Fix

The circuit board or fan motor may have shorted, causing a burning smell similar to gun powder to come from the air conditioner. If you suspect the fan has that burning smell, turn off the air conditioner and contact the manufacturing brand for professional help. Alternatively, use the services of another HVAC technician if the manufacturer is not readily available.

Another possible reason an air conditioner fan smells is that it may have caught some debris or small animal. But this may only apply to the condenser fan because of its location outside the house. If the smell comes from that area, check and clean the fan; do the same for the condenser and compressor.

air conditioner smells

Air Conditioner Has a Garlic Smell – Fixed

The garlic smell may come from the burning coolant. It is a rare occurrence and you may only notice it in a car air conditioner. However, it is best to let a technician check the refrigerant in the air conditioner if there is a strong garlic smell and determine whether or not it is burning and why. This applies to house and car air conditioners.

Air Conditioner Smells Like Vinegar – Solved

Your air conditioner may emit a smell like vinegar, sour to the nostrils. If you smell it, it may be a problem with the electric motor; if it emits too much ozone, it produces a vinegary smell. Turn off the air conditioner and contact a local HVAC technician to check the motors in the air conditioner and fix the faulty one.

The air filter may also be significantly clogged with dirt or the evaporator coil has too much condensation on it. Additionally, the ductwork may have mold in it or the drain pan needs cleaning. Follow the steps in this article to clean the filter, drain pan, and coils. But you will need professional help if the problem is with the ductwork.

Important Notes

The steps and instructions in this article cover all types of air conditioners: central air conditioning systems, portable units, split or ductless air conditioners, and wall or window units. You can also follow the steps to eliminate foul smells from an RV air conditioner. 

Follow directions in the user manual to locate various parts for proper removal, cleaning, and replacement. You may also need to hire a professional HVAC technician if you have trouble eliminating any bad smell from your air conditioner.

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