Burning Smell from AC Unit? Here’s What You Should Know.

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Woman in living room holding her nose from the burning smell from ac unit.

Updated November 3, 2021

We are approaching November in Florida, which means that in the next few months, you are going to be turning on your heater for the first time in months. When winter rolls around, concerned customers often call Scott’s Heating & Air Conditioning to report an odd burning smell from the AC unit when they first turn on the heat. It may be a sign that your HVAC system needs minor maintenance, or a more costly problem could be looming.

“You should never ignore a strong burning smell,” said Scott. “While it is most likely just burning dust particles, it could be a blocked duct or an overheated motor.”

What Causes the Smell of Burning Dust?

When your heater is not used for long periods of time, dust can collect on the heat exchanger and in the air ducts. When the heat is turned on, the dust burns off and releases an odor. It is normal for dust to burn off when the heat is turned on for the first time in the winter season and is not a cause for concern. However, the smell should disappear in a few hours. If the burning smell from AC does not clear, then further inspection is needed!

What Causes an Electrical Burning Smell from AC Units?

If you notice an odor that smells like burning plastic or burning electrical parts, it could be something more serious. For example, a foreign object in your HVAC system’s ductwork could start to smell once it gets overheated. Remove your air vent registers and visually inspect them. It could also be something more serious, such as an overheated motor or cracked heat exchanger. If the smell persists, call Scott’s Air to check the HVAC’s electrical components.

Troubleshooting the Burning Smell from Your AC

  • Check to See If Your Air Filter Is Clogged

    • We all sometimes forget to change out our air filters in a timely fashion. However, if you wait too long, the filter could pile up dust and debris, restricting airflow and straining the motorized components of your air conditioning unit. A similar burning smell could be emanating from these components.
    • Check the air filter and replace if it’s clogged. As a rule, try to change your air filter each month. If you have pets, your air filter might have to be changed out more often.
  • Closed Vents Could Be an Issue

    • If too many of the vents in your home are closed or blocked off, then it could be a reason for that burning smell. Your HVAC system tries to push out all the warm air to your home but when the vents are shut off, that air becomes trapped, causing a variety of issues for your system. Unlike cool air, you can actually smell too much heat accumulating in the ducts.
  • Could It Be System Damage?

    • Something other than dust may be burning. Your HVAC system can also overheat due to age, wear, and lack of AC maintenance. If the smell does not go away after a bit, you should turn off your system and call a professional HVAC technician to evaluate the problem for you.
  • You May Have a Broken Capacitor

    • An AC capacitor acts as a temporary battery for your air conditioning unit. It starts the motors in your system and keeps them operating by building and storing electricity. AC capacitors can break down for a number of reasons including power surges, overheated circuitry as well as general wear and tear.
    • If the capacitor is not performing optimally, it becomes very easy for the motors to overheat, giving off a burning smell. You will likely need a replacement for the capacitor.
  • Your Belt Drive Motor Needs a Replacement

    • Most AC systems either have a belt drive or direct-driven fans. In a direct drive configuration, the fan motor is connected to a shaft or fan axle which allows the fan blades to rotate at the same speed as the motor. In a belt-driven system, one or multiple belts connect the blades and the fan motor instead of the axle.
    • Over time, those rubber belts could wear down causing a burning smell to emanate from the AC unit. This is as simple as calling Scott’s Heating and Air Conditioning to come replace the belts as part of a maintenance visit.
  • You Could Have Electrical Failure

    • Many of these odors that we have previously discussed have a similar smell of dust burning. However, if you smell something that combines rotten eggs smell with burning plastic, you could be experiencing electrical failure.
    • There are plastic components that surround your wiring. If the plastic components protecting your wiring are compromised, you will notice the odor. Short circuits, worn electrical connections and defective breakers can all cause this issue.

If you are experiencing this smell, turn your system off immediately and call your local AC company.

“With winter coming, it is time for us to take a look at your heating system and perform maintenance to keep it working at its peak efficiency,” said Scott. “It doesn’t get too cold for too long in Florida, but when it does, we want our heat to work properly without emitting a nasty odor.”

Call Scott!

As we approach winter, it’s important that you check out your system before turning on the heat. A 20-point tune up from Scott’s Heating and Air Conditioning is all you need to ensure that your system is primed and, more importantly, safe to use for heating your home.

Schedule a 20-Point AC Tune-Up


Scott’s Heating & Air Conditioning is a full-service heating and air conditioning company and a Bryant® Factory Authorized Dealer in Central Florida. Whether you need repair, maintenance, or installation of a new heating or cooling system, we provide efficient, cost-effective, and professional service. When it’s hot, call Scott!

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Brooke Riley
Brooke Riley
Very professional, work very neat and cleaned up and removed stuff. Very impressed with all of the staff and the company.
Our AC decided to quit during one of the hottest heatwaves in years. We called Scott's and someone was at the house to give us a quote in 30 min. From the moment they answered our first phone call through the install everyone was amazing, professional and provided a quality product and excellent service. Craig, Jose, Dexter were awesome! One of the new guys brought us a portable unit at 9:30 PM on a Friday so we could sleep. We missed his name, but shout out to him as well (he likes to give high fives). Thanks Scott and team for everything. We highly recommend!!!
K Harper
K Harper
For the past week I've worked with Craig on getting estimates for a new A/C unit, and he has been great at answering my questions and addressing any concerns. Very responsive and knowledgeable, straight shooter and direct! I didn't have to deal with any up-selling like working with a used car salesman (I experienced that with other bigger local A/C companies providing quotes). For these qualities alone I would recommend Scott's A/C, even though I will disclose that we ultimately went with another quote from a family referral of an A/C company. Had that family referral not been apart of our consideration, we would definitely choose and recommend Scott's for new A/C installs and service!
Dan in sales, outstanding jobgoing over equipment and helping us make what was the best decisions for us on purchasing new a/cinstall, plus scheduling the next day!Boris and Justin were excellent with communications while install and after! very clean, professional taking old out and installing new!ty
We can't thank Scott's enough. We came home to a air conditioner barely limping along. I called Scott's first thing in the morning and they had a technician out that day. Unfortunately our system could not be saved. The salesman Craig came out that day as well and quoted a new system. Since it was a Friday we could not get the system installed until Tuesday. Scott's provided us with a portable system which definitely helped during the grueling heat wave in Central Florida. Tuesday came, the installers showed up on time and did an awesome installation job. Cleaned everything up and went on their way. Everyone was pleasant, professional and great to work with! Thank You Scott's Heating & Cooling!
Rodger Marty
Rodger Marty
Always happy with their response time. Issue started last night causing our A/C unit to shut down. Made a call to Scott's Heating and Air in the morning and a tech was here by 10:45am. Tyrie, the tech, is awesome. He quickly took care of the problem and had us up and running in no time at all. He is knowledgeable and professional and did a great job.
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Ron Brenton
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Bill Sumner
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Michael Imlay

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