Burning Smell from AC? 5 Common Causes and How to Fix It

A burning smell from the AC can be alarming. After all, a house fire is every homeowner's biggest nightmare. Fortunately, a burning odor emanating from the air conditioner or vents is not usually dangerous or indicative of a fire. The smell could indicate a relatively harmless air conditioner issue.

You might smell something burning when you turn the heat on for the first time during the heating season or after several months of disuse. Dust that settles in the ducts and on the furnace’s heating components burns off when the furnace is turned on. The smell usually dissipates quickly, but you might consider having your ducts and HVAC system professionally cleaned.

Air conditioners are also known for releasing various odors. The first step in discovering why your air conditioner smells is determining what the scent is reminiscent of. Dirty sock smells indicate one set of air conditioner problems, and vinegar smells suggest another. If the smell from your air conditioner reminds you of something burning, it can indicate several issues.

If your AC smells like burning, it could be worn out bearings, a dirty air filter, a damaged capacitor, electrical issues, or an overheating motor.

Air conditioning systems have two fans powered by motors. One fan and motor combo is located inside the house, and the other is located outside in the condenser. A motor’s metal bearings produce high-pitched squealing noises when they start wearing out. Worn-out bearings strain motors and cause them to overheat, creating a burning smell.

An HVAC technician can usually resolve this issue by lubricating the motor bearings. However, the motor might need to be replaced if too much damage has been done to the bearings or motor.

Air filters trap dust, pet hair, lint, and other contaminants in your home’s air to improve air quality and keep your HVAC system clean and performing well. How often to change an air filter depends on different factors, but they should be changed regularly, at least four times a year, or they become clogged with debris and restrict airflow through the system. Restricted airflow forces the blower motor to work harder to push air through the system, and the motor can overheat. A burning smell can come from an overheating blower motor or a dust-coated heat exchanger.

An overheated motor is one issue you can resolve yourself by changing the air filter if it appears dirty or hasn’t been changed in the last three months. If the filter is clean or if the burning smell continues after replacing the filter, there is some other issue that needs professional attention.

One clue that your air conditioner has a damaged capacitor is the smell of burning plastic from the outdoor condensing unit. A capacitor is an electrical component that kick-starts the compressor motor at the beginning of a cooling cycle. Overheating motors, power surges, and deterioration cause capacitors to go bad.

A damaged capacitor is a serious issue that requires immediate professional help. Shut off your air conditioner until a technician inspects it. The capacitor or motor might need to be replaced.

Electrical shorts, worn connections, and faulty breakers can cause the plastic coating on electrical wires and insulators to melt and produce the smell of burning plastic.

Electrical issues are serious and potentially dangerous. Electrical problems can damage other system components or start a fire. Immediately turn off the air conditioner and call an HVAC service.

An overheating motor can be a symptom of other air conditioner problems, such as worn-out bearings and dirty air filters. Additionally, aging motors must work harder and can overheat due to additional strain. Motor components sometimes melt when the motor overheats and produces a burning smell.

In some cases, the issue can be resolved without replacing the motor, but a motor that overheats due to age typically needs to be replaced. Professional HVAC technicians can diagnose the problem and perform necessary repairs.

A burning smell from your air conditioner is not typically a cause for alarm but can indicate serious issues. Electrical issues are potentially dangerous and can lead to electrical fires. Other matters like worn-out bearings, damaged capacitors, and overheating motors aren’t destructive but can lead to more costly repairs if neglected.

Turn off your air conditioner if you smell something burning. Check your air filter, and change it if it’s clogged. If the filter is clean and the burning smell persists, keep your air conditioner off until a professional HVAC technician checks out your system.