Turning Your Heat On? Look Out for These Sounds and Smells

A woman smelling something bad

As Florida temperatures begin to drop, homeowners can expect to begin using their heating systems. Before turning the heat on for the first time this season, look out for strange smells or noises that could indicate a need for heating maintenance or repair. At AC Designs, we’re here to provide all the information you need to keep your home comfortable all winter long. 

Tips for Turning Your Heat On

There are a few key tips to keep in mind this winter to ensure that your home is heated safely and efficiently. Test your system and thermostat controls ahead of time to make sure that it still functions properly from the previous winter season. 

Turn your heat on for a minimum of one hour and monitor your thermostat. If warm air doesn’t blow from your vents, contact your HVAC technician to troubleshoot. When it’s finally time to turn the heater on for good, gradually adjust your thermostat until you reach your desired temperature. 

Sudden setting changes can overwork your HVAC unit and cause harmful wear and tear. Instead of switching from cooling to heating overnight, start out on the lowest setting for maximized efficiency. You should also practice other ways to maintain efficiency throughout the winter. 

Keep your curtains and blinds open during the day to allow sunlight to naturally heat your home and reduce strain on your unit. Homeowners should also keep all windows closed to prevent heat from escaping the home. This can overwork your heating system and significantly raise your energy bill. 

Notice a Burning Smell From Heater? Don’t Panic!

An initial burning smell coming from your heat pump is normal after turning it on for the first time in months. This smell can be caused by a build-up of dust on your unit’s heat strips when the heating has not been used for an extended period of time. 

However, if strange smells persist after the heat has been in use for multiple cycles, consider calling a professional HVAC technician. AC Designs will send one of our highly trained professionals to diagnose the smell and ensure that your unit is functioning properly.

Troubleshooting Strange Sounds

Strange sounds coming from your heater can also be a normal part of turning your heating on after an extended time period. However, some sounds may indicate the need for a professional inspection. One common sound to look out for comes from the defrost cycle. 

This cycle occurs when the coil on your outside condensing unit becomes covered in ice or frost. This prevents the unit from functioning properly, causing it to go into the defrost cycle to thaw. Frost covering your unit’s coils is normal, and can sometimes cause a loud whooshing, grinding, or even sizzling sound. In some cases, steam may also appear.

Although they may be loud and alarming, these sounds are a normal part of the cycle as your unit’s coil defrosts. It is important to refrain from disrupting cycling by letting the system run and finish its process without interruption. Once the cycle is complete, your unit should be back to running efficiently.

Sources of Other Strange Sounds

Noises from the defrost cycle should only last 25-45 minutes around twice a day in colder temperatures. Other noises like whistling or squealing may indicate an airflow blockage or more severe problems with the belt or motor. 


Loud banging sounds coming from your unit after turning it on could indicate ductwork issues. While this noise may require loosening your ducts or adding thicker metal around them, banging noises are easy to remedy with the help of a certified HVAC technician.  


If your furnace or HVAC unit is making booming noises, contact your AC technician right away. These sounds could be caused by a gas build-up inside the unit, which can result in an explosion without a proper fix.


Squealing noises typically indicate problems with your unit’s belt or motor. Although unpleasant, these sounds are no cause for concern and typically only require minor repairs. 


If your unit is making a rattling or vibrating sound, this could be an indication of loose ductwork. Tightening the screws is a quick, simple fix to stop the rattling and readjust your ducts. 


Rumbling can be caused by issues within your unit’s burner as oil or gas uncontrollably burns. If a rumbling noise persists after your furnace is turned on, turn your unit off and immediately contact your AC technician. Continuing to run your unit can emit dangerous carbon monoxide into your home. 


Whistling sounds may be caused by airflow blockage and can often be fixed by changing your air filters and cleaning out your ductwork. If the whistling persists, contact your AC technician to further assess your unit.   

Join AC Designs’ Preferred Maintenance Program

If strange noises persist, contact AC Designs for professional help from our technicians. We encourage homeowners to join our preferred maintenance program for priority scheduling, replacement, and 24-hour emergency service to address issues with your unit as soon as possible 

Schedule an Appointment With Our HVAC Professionals

Turning your heat on for the winter can result in many strange sounds or smells as your unit adjusts. Keep these tips in mind as you turn your heating system on this season so you know when it’s necessary to call a professional for HVAC assistance. Schedule an appointment with AC Designs for all heater repair and maintenance needs.