An air conditioner shouldn't be producing an odor when switched on. At most, there may be a slight musty smell—suggesting that the unit's filters may need cleaning. But what about a burning smell? 

A Brief, Light Burning Smell

Just as dust can create an unpleasant, musty odor emanating from your air conditioner, it can contribute to a burning smell. When dust is a factor, any burning smell will be fleeting and should dissipate quickly. This is more likely to occur when the unit hasn't been used for an extended period of time. Dust that has settled on the unit's motor or capacitor has heated up, producing a burning smell. 


A burning smell produced by heated dust won't recur each time you turn your air conditioner on. When caused by dust, a burning smell is a good indicator that your unit needs to be cleaned (and its filters might require replacement). But if the odor is obvious each time the unit is activated and seems to worsen the longer the unit is in operation, this can be a sign of a more serious problem, and air conditioning repair is likely to be needed. 

AC Capacitors

Like most household appliances, your air conditioner has a capacitor. This releases a surge of electricity which activates the air conditioner's motor. A faulty capacitor can cause the unit's motor to overheat, and this can create the burning smell that your air conditioner is producing. However, the issue could just as easily be inside the motor.

Motor and Fan belt

An air conditioner's motor contains many moving parts. Its fan belt connects the fan to the unit's condenser (which regulates heat exchange to heat or cool your home), and if the fan is worn or broken, its rotations will create friction. The same can occur if the belt's bearings are loose or damaged. This can lead to spots of overheating within the unit, producing the burning smell emanating from your air conditioner's ducts. Prompt repairs are needed. Without intervention, the problem will become worse—as will the smell.

Burning Plastic

If the odor from your air conditioner smells like burning plastic (which will be acrid and have a harsh, chemical scent) then the overheating may actively be melting various plastic parts inside the unit. The resulting smell can be toxic, and your unit is a fire risk. Discontinue use immediately and arrange for urgent AC repair. 

Although a light, fleeting burning smell may simply be excess dust burning off, a recurring, lingering burning smell suggests that your unit needs quick attention. For more information on air conditioning repair, contact a company near you.