My Furnace Is Overheating! What Do I Do?
-
Few things are more alarming than realizing your furnace is overheating. If your furnace smells hot or shuts down unexpectedly, you're not alone. Furnace overheating is a common issue in New Jersey homes—and it can be dangerous if left unaddressed. However, don't panic. Understanding what's happening and taking the proper steps can protect your home, comfort, and wallet.
Read on to learn:
- What causes a furnace to overheat
- Signs and symptoms to look for
- How to fix an overheating furnace
- When to call a professional
What Causes a Furnace to Overheat?
Your furnace is designed with built-in safety features, but when internal parts get too hot, it will shut off to prevent damage or fire.
Here are the most common furnace overheating symptoms:
Restricted Airflow
- Dirty air filters can block circulation and cause the heat exchanger to trap heat.
- Closed or blocked vents make your system work harder and overheat.
DIY Check:
- Inspect and replace your air filter every one to three months.
- Check vents and registers to ensure they are open and unblocked by furniture, toys, or curtains.
Not sure what's going on? Schedule a diagnostic check with Air Experts.
Electrical or Wiring Failure
- Short circuits, loose connections, or aging wires can cause components to overheat.
- Blower motor or capacitor issues may lead to electrical overheating.
DIY Check:
- Turn off the power at the breaker.
- Look for scorched wires or a burning smell.
- If you notice either — stop and call a professional immediately.
Concerned about safety? Call us!
Dirt and Dust Buildup
- Dust on the blower motor, coils, or burners traps heat and reduces efficiency.
- Buildup can also block airflow, worsening the overheating issue.
DIY Check:
- Gently vacuum around the furnace exterior.
- Avoid opening internal panels unless you are properly trained.
- Schedule annual professional cleaning to prevent buildup.
Unsure what type of air filters are best for your home? Call us! We can help.
Faulty Thermostat or Temperature Sensors
- A malfunctioning thermostat may misread temperatures and cause your furnace to overwork.
- Damaged sensors fail to signal when to shut off heating cycles.
DIY Check:
- Test by lowering your thermostat 5°F — does the furnace shut off?
- Replace old batteries.
- If the problem persists, schedule diagnostic service.
Ready to upgrade to a smart thermostat? Book your service today!
Mechanical Wear and Tear
- Worn bearings, belts, or fan motors can overheat from friction or imbalance.
- Older furnaces often overheat because parts can't keep up with demand.
DIY Check:
- Listen for grinding or squealing sounds.
- These noises indicate it's time for repair or replacement.
Is your furnace over 8-10 years old or making unusual sounds? Schedule an appointment today!
What Happens When a Furnace Gets Too Hot?
So, what happens when your furnace gets too hot? When overheating occurs, these things may happen:
- The limit switch may trigger and shut off the system.
- You may feel lukewarm air from the vents or notice short cycling (the unit turning on and off quickly).
- Your heat exchanger may crack. Warning: A cracked heat exchanger is serious because it can release carbon monoxide into your home. Be sure to install CO2 detectors and never ignore any signs of overheating.
How to Fix a Furnace That's Overheating
As a homeowner, it's crucial to know what to do—if and when—your furnace starts overheating. Here's a quick step-by-step guide.
- Turn off the system immediately.
- Shut off the power switch or breaker to prevent further damage.
- Replace your air filter.
- A dirty air filter is a top cause of overheating — it's quick and inexpensive to fix.
- Check for blocked vents or areas with dirt.
- Ensure airflow is unobstructed.
- Inspect your thermostat.
- Ensure it's functioning properly and accurately calibrated.
- Allow the system to cool.
- Wait 30 minutes before restarting. If it overheats again — stop and call an Air Experts pro.
Can an Overheated Furnace Cause a Fire?
In rare cases — yes. While modern furnaces have multiple safety mechanisms (like limit switches and thermal sensors), continuous overheating may melt wiring insulation, ignite nearby debris, and damage the blower motor or gas valves.
To help prevent your furnace from overheating and shutting down:
- Keep the area around your furnace clear of debris
- Schedule annual maintenance
- Replace outdated systems before parts fail
How Long Can a Furnace Run Before Overheating?
There's no fixed time, but most furnaces run 10–15 minutes per cycle. If your unit runs constantly or cycles on and off quickly, it could be overheating or struggling to maintain airflow.
When to Call in the Pros
Call an experienced HVAC technician if:
- The furnace shuts down repeatedly.
- You smell burning, metal, or electrical odors.
- You hear grinding, squealing, or rattling.
- The system trips the breaker or shows error codes.
Schedule your appointment now at 732-759-0934.