Why Is There a Burning Smell Coming From My AC?

Burning Smell From AC (Blog Cover)

A burning smell from AC units is a common abnormality. So if you are noticing a burning smell from your AC, don’t be alarmed. 

Many people think that this may be a sign of a fire hazard, but that is rarely the case. Still, you should pay close attention and take action as soon as possible if you notice a burning smell from your AC unit. 

In the following post, Air Essentials Inc looks at some of the most common causes of a burning smell coming from your AC and goes over some tips to address the problems.

Dirty Air Filter

Different rules apply to how often you should change your AC’s air filter depending on what type of system it is and if you have sensitive allergies. The job of an AC’s air filter is to trap particles that come from outside and prevent them from cycling into your indoor air. 

But when the air filter is too old, the blower fan has to work harder to produce the proper airflow. When the fan is overworked, it can result in a burning smell. Again, this probably won’t result in a fire hazard, but it could cause your fan to blow out and can even cause a spike in your energy bills. 

For central AC systems, it is generally recommended to change the air filter every three months. However, if you have sensitive allergies, you may want to change the filter every 45 days. 

Capacitor Issues

The capacitor is a crucial component of your AC unit. The capacitor is responsible for providing the initial jolt of power to the motor when it is kicked on. In most cases, the capacitor will give off a powerful jolt of electricity to provide the power needed for the AC motor to get up to speed. 

If the burning smell you are detecting is more akin to burning plastic, there is likely a problem with the capacitor. Stand near the vents outside your house when your AC is running. If the smell seems stronger near these vents, that is even more robust evidence that the capacitor is either broken or malfunctioning.

A broken capacitor is a fairly serious issue, and unfortunately, it cannot be solved as simply as a dirty air filter. You should call out an HVAC professional as quickly as possible. Also, if you suspect that a faulty capacitor is causing the burning smell from your AC, turn the AC off and don’t rerun it until addressing the problem.

Melting Drive Belts

Some AC units use belts to generate power for the motor blower. They are similar to the drive belts in your car’s engine. Like automotive belts, your AC drive belts can get worn down and melt in extreme cases. If you notice that the smell coming from your AC is more akin to burning rubber (say, from a tire), then the problem is likely a worn down or melting belt. 

If this is the smell you are picking up on, the solution may be as simple as replacing the drive belt. You will need to open up your AC unit and have a closer look. Again, if you don’t feel comfortable doing this yourself, it’s always best to call on a professional.

Dust Buildup

If it has been a long time since you last turned on your heating or AC unit and noticed a burning smell, the culprit could be dust buildup. Unfortunately, when your HVAC systems sit idle, it doesn’t mean that they aren’t collecting dust and debris. 

However, when they are suddenly turned on after months of being idle, some of that dust and debris can start to burn off because of the heat generated from the HVAC system’s motor, resulting in a burning smell from AC units. 

The best way to tell if this is the case is to note how long the burning smell lasts. If you notice that the smell goes away after a few minutes of running your AC, then the culprit is most likely dust buildup. While the problem should go away the more you run your AC or heater; you shouldn’t allow dust to build up often.

The best way to avoid this issue is to call an HVAC professional to clean and run maintenance on your HVAC system in the offseason (any months your heater or AC usually aren’t used). 

Worn Out Bearings

Your AC motor will have bearings that fit between the armature and the motor’s housing. The purpose of these bearings is to allow the moving parts to rotate without causing excess friction. Naturally, the bearings will wear down over time, resulting in excess friction between the armature and motor housing. A burning smell can result from this friction.

If all the other components we have mentioned seem to be working fine and you have recently run your AC, the bearings may have to be lubricated or replaced. It is best to address this issue as soon as possible because if your AC runs with worn-out bearings for too long, it may damage the motor beyond repair. 

Solving Your AC Issues

Whether you have a burning smell from AC units, uneven heating, or need an all-new HVAC system, we can help. Let Air Essentials Inc expertly solve all of your HVAC issues.