What can cause a furnace to overheat?

4 Possible Reasons Why Your Furnace is Overheating

  • Old age. The average lifespan of a furnace is between 15 to 25 years. …
  • Airflow issues. Airflow issues are the first thing to investigate when faced with a furnace that overheats. …
  • Dirty components. …
  • Mechanical failure.

How do I stop my furnace from overheating?

Your furnace could overheat due to a short circuit or inadequate circulation. Scheduling regular furnace tune-ups is the best way to make sure that the moving parts in your furnace are in good, working order. Regular tune-ups also enable technicians to spot signs of strain and premature wear.

How do you know if your furnace is overheating?

Signs of Furnace Overheating

  1. The Odor. This is the most common and obvious sign of furnace overheating. …
  2. Frequent On-Off. Another giveaway of furnace overheating is that the furnace may turn on and off again and again. …
  3. Noisy Furnace. …
  4. Restricted Airflow. …
  5. Short Cycling. …
  6. End of Lifecycle. …
  7. Dirt Deposits.

Will a furnace shut off if it overheats?

Your furnace may be shutting down because the heat exchanger is overheating. When the heat exchanger overheats, the furnace shuts down to protect it from cracking. When the exchanger cools, the furnace cycles back on.

How do you reset a furnace after overheating?

How to Reset Your Furnace

  1. Turn down the thermostat to its lowest setting.
  2. At the circuit breaker, turn off the power to the furnace.
  3. If this is a gas furnace, turn off the gas supply at the valve for the main gas pipe, but leave the pilot’s gas supply on.
  4. If the pilot light was out, light a match to relight it.

Can my furnace catch on fire?

Yes, a furnace can catch fire.


The following are reasons your furnace can catch fire: Your furnace’s air filter is blocked. Your furnace’s gas pressure is too high. There is a crack in your furnace’s heat exchanger.

Can my furnace explode?

Although it is possible for a gas furnace to either catch fire or explode, it’s highly unlikely. If there is a danger of this happening, the furnace will usually simply shut off—as it’s designed to. … If you’ve got a good furnace and take care of it, you won’t have to worry about explosions or fires.

Should furnace be hot to touch?

Most single stage furnaces should be just uncomfortable to touch on the main trunk just above the main unit. As Heat rise levels can range from 50-70 higher than ambient air temp. Yes, it’s normal.

How often should you change your furnace filter?

In general, this is how often changing furnace filters needs to be done: For 1- to 2-inch filters, replace them every 1 to 3 months. For 3- to 4-inch filters, replace them every 6 to 9 months. For 5- to 6-inch filters, replace them every 9 to 12 months.

Why does my furnace keep running?

A dirty furnace filter is the number one reason we’ve found that furnaces run constantly. The air filter captures dust, pet hair, and debris that could damage the furnace and keeps it from getting to the heat exchanger. If the filter is dirty, it restricts airflow across the heat exchanger, which causes it to overheat!

Where is the reset button for the furnace?

Locate the reset button on the furnace and press it to reset the furnace. It is usually located inside the blower compartment on the side of the blower motor. Be cautious as the housing may be hot. If the button is popped up, press it down.

Why is my furnace running every 15 minutes?

A standard heating cycle varies from 10 to 15 minutes depending on your insulation and weather. Once the temperature of the interior air becomes too low, the thermostat will distribute a signal to activate the furnace.

When should a furnace be reset?

If your furnace doesn’t have any air coming out at all and the pilot light is out, it’s worth it to try resetting the furnace. If this doesn’t work, there may be a problem with the thermostat setting, the power, or the gas line.

How do you reset a furnace blower motor?

How to Find and Reset your Furnace Motor Blower

  1. Step 1: Turn off the power to the furnace. …
  2. Step 2: Remove the blower compartment cover. …
  3. Step 3: Make sure the blower is completely cooled off. …
  4. Step 4: Locate the reset button. …
  5. Step 5: Press the button in (assuming that this is your issue and that the button has popped).

Where is the furnace circuit breaker?

It’s usually located on the side or top of your machine. It can also sometimes be found mounted on the wall near it. This is because the furnace disconnect code often requires this switch to be close to your furnace. This switch adds a layer of safety to operating your furnace.

Why is my furnace screeching?

Furnaces can make squeaking noises for a variety of reasons. In general, it means that a part inside of your furnace needs to be replaced or fixed. This can be anything from the blower belt fraying, to the blower or inducer motor wearing out over time.

Can turning on the heat start a fire?

The National Fire Protection Association says more than one in six home fires start from heating equipment, which is the second most common cause of a fire behind cooking. While most heating-related fires start from either space heaters or fire places, more than one out of every 10 starts with a central heating system.

Can heat registers cause fires?

Fire Hazard

Perhaps the most obvious (and most dangerous) result of a blocked vent is that it will cause a fire. How? When you’re forcing your system to overwork, as mentioned in our first point, you put your furnace at high risk of setting on fire.

How do I know if my furnace is leaking carbon monoxide?

Signs of Carbon Monoxide Leaks

  1. Soot: You may notice soot-like stains on your furnace. …
  2. Smell: While carbon monoxide doesn’t emit odor, it may get accompanied by other exhaust gases that produce an odor.
  3. A yellow burner flame: The pilot flame may produce an unusual yellow flame instead of the normal blue one.

Why is my furnace exploding?

What is delayed ignition? When your thermostat calls for heat from the furnace, a gas valve opens, sending gas to the furnace’s burners to ignite the gas. … The gas keeps building until—BOOM—it reaches a flame and finally ignites, causing a small explosion in your furnace.

What does a bad furnace sound like?

There are a variety of problems that can cause your furnace to produce loud noises. Types of noises such as scraping, banging, whistling, and popping may be a sign of a loose part, cracked heat exchanger, or dirty gas burners.

Is it OK to run your furnace without a filter?

Technically, you can temporarily run a furnace without a filter. However, it’s important to emphasize the word “temporarily” here. … Poor air quality: For one, not having a filter in place means there is nothing to prevent dust and debris from being sucked into your furnace and recirculated throughout your home.

What happens if you never change your furnace filter?

Short Cycling. If the air filter is not serviced often enough, it will eventually become clogged to the point that air cannot pass through it. When the furnace is operating, the lack of air flow will trap the heat in the system. … Without a new air filter, the furnace will overheat every time it starts up again.

How much does it cost to replace a furnace filter?

Changing Your Furnace Filter

Costs for new filters range based on brand but tend to be around $10 to $30. The filter keeps dust and dirt from your furnace components and improves your air quality. Some annual inspections will include changing and cleaning this part of the unit.

Why won’t my furnace shut off?

If your furnace won’t turn off, the easiest issue to fix is your thermostat. … A furnace that is working hard to keep a high temperature, especially when it’s extra cold outside, can seem to run continuously. The second common thermostat problem is the fan switch. Your fan can be adjusted manually from your thermostat.

Why won’t my heat stop running?

There are a couple potential reasons why your heating system won’t turn off: Bad thermostat: A faulty thermostat can normally be repaired. Faulty wiring, a broken switch, or broken heating sensor can be fixed depending on how severe the issue is.

Why is my furnace not stopping?

If the air that the furnace is blowing is hot, that means that the furnace burners aren’t turning off. Two very common causes are that the thermostat is set too high, or the filters being dirty. … Sometimes, no matter what, an expert is needed to properly diagnose and service a malfunctioning furnace.

Do all furnace blower motors have a reset button?

All furnaces are equipped with a reset button. They are generally red or yellow and are located inside the blower compartment. The reset button is a safety feature that will shut down the furnace when a problem is detected, often a hot or overheating furnace, before it trips the circuit breaker.

Why does my furnace turn off after a few minutes?

Low airflow

When the exchanger heats up to the maximum temperature, the furnace shuts off after a few minutes. … The furnace won’t be able to pull fresh air into the blower if the air filters are clogged with dust, pet hair, and other debris. You should also make sure to open all of your air supply vents.

How do you clean the flame sensor on a furnace?

Flame Sensor Cleaning – Furnace Cycling On and Off – YouTube

Is it normal for my heat to come on every 10 minutes?

With all that being said, if there are no extreme factors involved, the average run time for a furnace is 10-15 minutes per cycle. Your furnace may need to run two to three times an hour to maintain your desired temperature if your home has average insulation.

Why does my furnace keep shutting off after a few seconds?

A common reason a furnace short cycles is because the heat exchanger, the part that heats your air, is getting too hot due to a lack of airflow. Once the heat exchanger overheats, it trips the high limit switch, which shuts the furnace down to protect it.

How do you know a thermostat is bad?

7 Signs You Need to Replace Your Thermostat

  1. Your HVAC Keeps Turning On or Off. …
  2. Faulty Thermostat Readings. …
  3. Suspiciously High Energy Bills. …
  4. Constant Temperature Shifts. …
  5. Thermostat Is Too Old. …
  6. Thermostat Fails to Respond to Changed Settings. …
  7. Your HVAC System Short Cycles.

Why is my furnace running but no heat?

Dirty filters are the most common cause of furnace problems. Dust and dirt restrict airflow—and if the filter gets too clogged, the heat exchanger will overheat and shut off too quickly, and your house won’t warm up. If the blower is running but no heat is coming out, replace the filter.

Why does my furnace only work sometimes?

If your furnace shuts off too often, you could have a corroded or dirty flame sensor. A flame sensor lets your system know there’s a flame when the gas valve is open. If there isn’t a flame, the sensor will shut off the gas valve to keep the gas from getting into your house.

How do you troubleshoot a furnace?

Furnace Troubleshooting Recap:

  1. Clean or replace air filter.
  2. Troubleshoot thermostat problems — replace batteries if necessary.
  3. Set thermostat to heat and at a higher temperature than the current room temperature.
  4. Check electrical panel for blown fuses or tripped breakers.
  5. Make power switch near furnace is flipped on.

How do I know if my furnace blower is bad?

Signs of an Overheating Blower Motor

  1. A “hot” or burning smell from vents in the home. This symptom is often coupled with the furnace shutting off completely. …
  2. Loud humming and other unusual noises. We have many homeowners call us mentioning humming and other odd sounds. …
  3. Furnace cycles off and refuses to restart.

How do I know if my furnace blower motor is bad?

What Are Signs Your Blower Motor Needs to Be Replaced?

  1. Poor or Airflow from Air Vents. This will be the first and most obvious sign your blower motor has a problem. …
  2. No Airflow At All From Vents. …
  3. Skyrocketing Energy Bills. …
  4. Strange Noises When You Turn on the Heat. …
  5. Overheating Blower / Weird Smells.

How do I know if my HVAC blower motor is bad?

7 Signs and Symptoms of a Bad AC Fan Motor

  1. AC Fan Doesn’t Start. Even though you have the AC turned on, the fan does not start.
  2. AC Fan Doesn’t Stop. …
  3. Slow Rotating Blades. …
  4. Outside Fan Blades Are Still. …
  5. Rattling, Humming, and Buzzing Noises. …
  6. AC Runs Intermittently. …
  7. No Cold Airflow.

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