If your furnace is overheating, there’s a problem, and it’s usually due to airflow or mechanical issues. But overheating means your furnace is protecting itself to prevent further damage. This article delves deeper into some reasons your furnace is overheating and what you can do about it.
Quick Takeaways
- Your furnace overheating is usually due to airflow or mechanical issues.
- A dirty air filter is the most common reason.
- A furnace overheats to prevent damage or fire risk and triggers safety shutoffs.
- Repeated overheating can damage the heat exchanger and blower motor.
- If you ignore the overheating, the system may shut down or cause safety hazards.
- Some checks you can do yourself; most require a professional technician.
What It Means When a Furnace Overheats
When your furnace overheats, it means the system’s internal parts are getting too hot. This rise in temperature triggers the furnace’s “high limit switch” to turn off, in order to prevent damage or a fire.
The high limit switch continuously monitors the furnace’s internal temperature and turns it off when temperatures get too hot. It then activates the blower fan to push excess heat out of the system.
Common Reasons a Furnace Overheats
1. Dirty or Clogged Air Filter
A dirty or clogged air filter restricts airflow, preventing proper air circulation. This results in heat getting trapped inside the furnace.
2. Blocked Supply or Return Vents
Furniture, rugs, or closed vents disrupt the airflow balance. This imbalance traps heat inside the furnace.
3. Blower Motor or Fan Problems
Blower motor or fan problems result in weak or failing airflow. The furnace can’t push hot air out, causing heat to build up inside the unit.
4. Faulty Limit Switch
A faulty limit switch can’t effectively monitor the furnace’s internal temperature, resulting in repeated shutdowns or even false overheating signals.
5. Cracked or Damaged Heat Exchanger
A cracked or damaged heat exchanger allows heat to leak into your furnace cabinet rather than directing the heat into the ducts. Besides causing a heat buildup, carbon monoxide may leak into your home, creating a safety hazard.
6. Ductwork Restrictions or Collapsed Ducts
Airflow bottlenecks severely limit airflow, preventing heat from the furnace from circulating properly. This results in rising furnace temperatures.
7. Improper Furnace Size or Installation Issues
An oversized furnace heats your home too quickly, causing a rise in the furnace’s internal temperature. Before heat can properly circulate, the furnace shuts off. Once it cools off, it turns on again, resulting in a rapid on/off cycle (short cycling).
Warning Signs Your Furnace Is Overheating
Here are some warning signs that your furnace is overheating and needs immediate attention:
- Furnace shuts off quickly after starting
- There’s a burning or metallic smell
- The noise from the blower motor is loud
- There’s an error code on the thermostat or control board
- You’re getting weak or no airflow from your vents
- Furnace restarts repeatedly
Is an Overheating Furnace Dangerous?
Yes, an overheating furnace can be very dangerous. The heat buildup inside the furnace can damage the unit’s internal components, like the blower motor, wires, and the heat exchanger.
In some cases, the high internal temperature can also ignite flammable materials inside your furnace cabinet. There are carbon monoxide concerns, too. Overheating can crack your heat exchanger, allowing carbon monoxide to leak into your home. This colorless and odorless gas can cause nausea, dizziness, and even death.
Keep in mind that your furnace has a high limit switch that shuts down the system when the internal temperature gets too high. This safety shutdown exists to keep you safe and prevent fires or damage to your home.
What You Should Do If Your Furnace Overheats
Here are some safe steps you can take if your furnace overheats:
- Turn your furnace off immediately.
- Check your air filter. If it’s clogged, replace it.
- Make sure your vents are open and nothing is blocking them, like furniture or rugs.
- Don’t keep restarting your system.
If your furnace is still overheating, turn it off and contact one of our licensed technicians at Orlando One Hour.
When to Call a Professional for Furnace Repair
We understand that it’s not always clear when you need furnace repair services. However, here are some clear signs that a professional inspection is necessary:
- Your furnace repeatedly shuts down
- There are burning smells
- There doesn’t seem to be any airflow
- There are error codes on your thermostat
- Your furnace is old
- You hear strange sounds, like banging or whistling
- Your pilot light isn’t blue
When you notice these signs, contact our team at Orlando One Hour. We can inspect your furnace, diagnose the issue quickly, and make the necessary repairs so that your home is safe and warm.
FAQ — Furnace Overheating Questions Homeowners Ask
Why does my furnace keep shutting off from overheating?
If your furnace keeps shutting off (short cycling), it could be due to restricted airflow or mechanical issues, like a cracked heat exchanger. Your furnace may also be too large for your space.
Can a dirty filter really cause a furnace to overheat?
Yes! A dirty filter restricts airflow, preventing the heat from effectively circulating into your home. This traps the heat in the furnace, causing a heat buildup.
Is it safe to run a furnace that overheats?
No, you shouldn’t run a furnace that overheats. Once your furnace’s internal temperatures get too high, your limit switch kicks in, automatically shutting your furnace off to prevent damage or fires.
Can I fix an overheating furnace myself?
This isn’t a good idea. There are a few DIY steps you can take, such as changing your air filter and checking the vents to ensure they aren’t closed or blocked. Anything beyond that should be left to professional technicians.
Does furnace overheating mean I need a replacement?
Not necessarily. Your furnace overheating could be an easy fix, such as changing air filters, fixing a collapsed duct, or replacing a flame sensor. However, if a major component is irreparably damaged, you may need to replace your furnace. You may also need a replacement if your furnace is old or is too large for your home.
Get Fast, Reliable Furnace Repair When Overheating Strikes
When your furnace overheats, it signals a serious problem. If simple DIY steps, like changing your air filter or opening vents, don’t solve the issue, a professional diagnosis is necessary.
Contact our technicians for a thorough inspection. We serve Orlando and the surrounding areas, and we’re always on time or you don’t pay a dime.
When you contact us for furnace repair services, our priority is protecting your home, your system, and your safety.