What is Causing My HVAC Furnace to Overheat?

Nov 28, 2022

As we approach winter, our furnaces will become a critical component of the comfort of our homes. Unfortunately, this is the time of year when people realize their HVAC unit is struggling, with a common problem being overheating. An overheating furnace is extremely dangerous to the health and safety of a home; therefore, we recommend watching out for these warning signs and fixing them immediately if they occur. 

Warning Signs of an Overheating HVAC Furnace

regular hvac overheating problems

When an HVAC furnace overheats, there are clear HVAC warning signs for homeowners to recognize easily. Sadly, many homeowners, especially new homeowners, are often unaware of the signs, or if they do remember them, they ignore their unit in the hope that it will “fix itself.” Woefully, HVAC furnaces don’t just fix themselves, but you can take advantage of these red flags. 

  1. A low humming noise your HVAC unit doesn’t usually make
  2. A consistent burning aroma that lasts far longer than “burning off summer dust”
  3. A unit regularly clicking off before completing its cycle

Carbon Monoxide Warning Signs from Your HVAC Unit

Before we delve deeper, we want to note the severity of carbon monoxide. Many homeowners will notice a faint burning smell when they turn on their furnace for the first time since spring; this is the scent of dust burning off, and it will last approximately 30 minutes. If the smell continues beyond those 30 minutes, that is a red flag that your HVAC furnace is overheating to dangerous levels. 

When your HVAC furnace overheats to these severe levels, it can cause stress fractures in the heat exchanger, the unit component that pushes exhaust gas out of the home. When it cracks, the gas will leak into your home. Carbon monoxide is a colorless, odorless gas that results in 50,000 people visiting the hospital annually due to accidental poisoning and an average of 400 deaths. 

To prevent such tragedies, installing a carbon monoxide detector in your home is highly recommended. If you notice the burning smell lasting too long, instantly turn off your HVAC unit, open windows and doors, and call your HVAC specialist immediately

4 Reasons Your HVAC Furnace Will Overheat

The Air Filters are Clogged

The Benefits of Regular HVAC Maintenance

The first, and easiest to fix, reason why your HVAC unit may be overheating is that the air filter is clogged. Clogged air filters block the appropriate airflow, making the furnace work harder to push the air through. As a homeowner, you should have a note in your calendar to replace your filter according to its size schedule. By regularly checking and replacing the filter, this problem can be easily prevented. 

There’s Build-Up on Internal Components

This reason for overheating is actually a result of problem #1. When your air filter gets clogged, dust, dirt, and debris stay inside the system and coat internal components with a thick layer of yuck. That grime will prevent the internal components from functioning correctly, such as the heat exchanger no longer moving heat and the blower motor being unable to provide ventilation. Again, homeowners should regularly perform air filter replacements to prevent such a problem from occurring in the first place. 

Short Cycling is Happening Regularly 

Does your HVAC furnace click on but seems to click off before the house is to the temperature you indicated? This is called short cycling, which places unnecessary strain on the unit as it turns off and on too frequently since it does not complete the cycle duration in full. 

A variety of reasons can cause short cycling, but the most common is that the unit is overheating. It can also be traced back to a failing thermostat or when a furnace unit is too large for the house. When you notice this frequent short cycling, we recommend calling in a pro before expensive repairs become required. 

The HVAC Furnace is about to Die

Last, and the most problematic of them all, as to why your HVAC furnace is overheating is because the unit is failing as a whole. When components of an HVAC unit start to fail, it creates a domino effect on the other components since they have to overwork to make up the excess strain. If you notice your HVAC system straining, we recommend calling an HVAC technician to diagnose your problem. Remember, it is far easier and affordable to replace a single failing component in advance than letting it take down the whole unit with it. 

PRO TIP: Read our past article on whether or not it is time to repair or replace your HVAC system. 

The Benefits of Regular HVAC Maintenance

overheating hvac furnace warning signs

While it may seem like another expenditure on your home maintenance list, your HVAC furnace is one of the most critical aspects of your home you should keep as a top priority. Regularly scheduled HVAC maintenance, including small DIY tasks for the homeowners and comprehensive preventive care by professional technicians, will save you money in the long run. Plus, it helps you maintain the unit’s warranty, so if something goes wrong, you are not required to pay for it out of pocket! 

Choose Apollo Heating & Air Conditioning

We understand how vital a functioning HVAC furnace is, especially during the cold month of winter here in the Tri-Cities. That’s why our service team is available 24/7 to aid you in troubleshooting, diagnostics, maintenance, repairs, or replacement of your HVAC equipment and systems. To schedule a service with our team of factory-trained and certified HVAC technicians, please complete our contact form.