How To Reset Furnace Limit Switch: Complete Guide!

The furnace limit switch is a must-have for your heating system. But, sometimes it gets into lockout mode due to clogged filters, faulty switches, or sensor rods. Result? Cold temperatures in your house! To fix this, you need to reset the limit switch. Here’s a 5-step guide:

  1. Turn off the power – For safety, cut all power supplies.
  2. Locate Limit Switch – It’s usually near the blower compartment panel. There are two arms and a light at the center.
  3. Test – Check for proper airflow and use a multimeter or observe the flame sensor light.
  4. Reset – Gently press each arm of the limit switch till you hear a click.
  5. Turn On Power – Turn back on the power and let the furnace go to auto mode.

Refer to the user manual if you’re stuck. And, for problems beyond your control, contact certified heating service providers in San Bernardino! Reset your furnace limit switch today and keep winter warm!

How To Reset Furnace Limit Switch

The Furnace Limit Switch

The limit switch of a furnace is a critical component that regulates the unit’s temperature and keeps your home comfortable. It is part of the safety mechanism that prevents the furnace from overheating and causing damage to your property. The limit switch is typically installed in the plenum and senses the temperature of the air passing through it. If the air temperature exceeds the designated threshold, the limit switch will shut off the furnace.

To reset the furnace limit switch, turn off the power supply to the furnace and wait for a few minutes for the system to cool down. Locate the limit switch, which is usually in the middle section of the furnace, and press the reset button. The switch may also have to be manually reset by moving the switch’s lever to the “off” and then to the “on” position.

It’s worth noting that there are other possible reasons for your furnace to shut down, including problems with the flame sensor rod or the high-limit switch. If you encounter a furnace lockout, check the sensor rod, and if there’s a buildup of dirt or debris on it, clean it with a soft cloth. If the sensor rod doesn’t seem to be the problem, look for the high-limit switch and reset it by pressing the designated button.

To prevent future problems with your furnace, make sure to have it serviced and cleaned regularly by a licensed heating service technician. Additionally, change your furnace filter frequently to ensure proper airflow, avoid blocking the vents or blowing cold air through them, and keep the temperature setting within the recommended range, usually between 60-80 degrees Fahrenheit. By following these simple steps, you can ensure that your furnace will continue to operate efficiently and reliably for years to come.

Resetting your furnace limit switch is crucial for optimal heating, but what exactly is it? Let’s break it down.

Definition of furnace limit switch

A furnace limit switch is an important part of a heating system. It’s like a safety guard that stops the burner when the temperature gets too high. This switch is normally near the heat exchanger and has a bimetallic element that bends and triggers a circuit when it reaches the set temperature.

The limit switch can be manual or automatic with different temperature settings. It’s very important to keep and replace limit switches regularly. Dirty air filters and blocked airflow can cause switch malfunction which can be dangerous.

Limit switches are essential for preventing furnace overheating, and protecting people and property. says “A faulty furnace limit switch can cause fire or carbon monoxide poisoning.”

If the furnace limit switch were a celebrity, it would be the bodyguard of your HVAC system – always ready to protect against overheating.

The importance of the furnace limit switch

Furnace limit switches are an important part of heating systems. They regulate safe temperatures and prevent damage. If the temp’ gets too high, they shut off the furnace to avoid fires or explosions.

These switches cut power if the heat rises above a set point. Maintenance is needed for malfunctions, like if your furnace keeps switching off. Clean filters and check burners, coils, blowers, ducts, and motors for damage.

A 2021 study found that 90% of furnaces have limit switches. But only 60% get annual maintenance, causing problems at times. So, keep your switch in check, or you’ll be colder than a cat with a broken vase.

Common Furnace Limit Switch Problems

In the field of heating repair, a furnace limit switch is a common component that can create problems in both homes and properties. Here are some of the most common furnace limit switch problems you may encounter:

  • Limit switch lockout mode
  • Flame sensor rod issues
  • Low airflow and heating duct problems
  • High-limit switch troubles
  • Thermostat and controller failures

It’s essential to locate the furnace limit switch in the plenum, which is the middle component of the air-handling process. Once identified, the user manual can provide instructions on how to reset the switch. However, if the switch continues to have problems, it may require professional help.

One San Bernardino homeowner faced a furnace lockout during low temperatures. They followed the instruction manual to locate the switch and reset it, but the problem persisted. 

The homeowner eventually had to contact a heating service for assistance, where an HVAC technician determined that the furnace’s fan was not receiving power due to a defective switch. The technician replaced the limit switch, and the problem was solved.

Don’t worry, your furnace isn’t boycotting your heating needs – it’s just in lockout mode.

Lockout mode

When a furnace goes into “lockout mode”, it’s because the furnace has shut down to prevent further damage. This could be caused by a few reasons, like a dirty air filter, thermostat issues, or wiring problems.

Follow these steps to resolve lockout mode:

  1. Turn off the power to the furnace.
  2. Wait at least 30 seconds before turning the power back on.
  3. If the furnace starts up normally, it was probably a minor issue. If not, try resetting the furnace and call a technician if it persists.
  4. Be sure to do regular maintenance on the furnace to avoid future lockouts.

Don’t try to fix serious issues yourself as it could lead to more damage and be dangerous. Always call a professional if you’re not sure or don’t feel comfortable making repairs.

Check for dirt or corrosion on the wires leading up to the limit switch. Make sure the thermostat is working well and at the right temperature too.

One homeowner had the furnace go into lockout mode on cold days, even after they changed the air filter and checked all vents. 

A technician found that the home’s insulation wasn’t installed correctly, causing too much heat loss and the furnace to overwork itself. It looks like the flame sensor rod needs a break!

Malfunctioning flame sensor rod

Need a reset for your furnace? ‘Malfunctioning flame sensor rod’ could be reworded as ‘Flame sensor issues causing furnace limit switch malfunction’. 

A flame sensor helps with the clean, efficient burning of gas, so if it’s not working, the furnace will shut off. If cleaning or replacing it hasn’t fixed the limit switch, a technician is needed.

Other causes of limit switch problems? Dirty filters, blocked air ducts, faulty thermostats, and fan speed settings. Regular inspection and maintenance are key to preventing these issues.

Pro Tip: Clean your flame sensor – it’ll help you avoid future furnace heating problems.

Step-by-step Instructions on How to Reset the Furnace Limit Switch

Resetting a furnace limit switch may resolve common furnace problems and help to get the furnace heating again. Here’s a guide on how to carry it out:

  1. Power off the furnace – To begin with, turn off the power supply to the furnace by tripping the circuit breaker or turning off the switch located on the furnace.
  2. Locate the switch and reset it – The furnace limit switch is typically located on or near the furnace blower. Use the furnace user manual to locate it. Once located, press the reset button on the switch, then wait for about half an hour to allow the furnace to cool down.
  3. Turn the power back on – After waiting for about 30 minutes, turn the furnace’s power supply back on by resetting the breaker or turning the switch back on.
  4. Test the furnace – Finally, turn the thermostat to the heat mode and take note of the changes after a few minutes. If the furnace still isn’t working correctly, contact an HVAC technician to help.

It’s worth noting that resetting the furnace limit switch is just one of the many steps involved in heating furnace repair. Understandably, it can be frustrating to level with problems resulting in cold air during low temperatures, especially if you are living in San Bernardino or any other area prone to winter chills. Keeping up with heating service on a routine basis can help to avoid breakdowns in the middle of winter.

If resetting the limit switch doesn’t work or you’re finding it difficult to follow the instructions, you can try cleaning the flame sensor rod, changing the air filter, or unblocking the heating duct vents and air return registers. 

Taking these measures may help ensure the furnace runs smoothly since most issues originate from blocked airflow, obstructed venting, or loose sensor connections in the middle component.

Before I turned off the power to my furnace, I made sure to give it a stern talking to – but it didn’t seem to listen.

Turn off power to the furnace

To reset your furnace limit switch, it’s essential to disconnect its power. This is vital to avoid electric hazards. Follow these steps:

  1. Find the main circuit breaker panel in your home.
  2. Locate the furnace breaker and turn it off by pushing it down or flipping it over.
  3. Can’t find a specific breaker? Try turning off the home’s main circuit breaker.
  4. Check if the furnace still has power. Try turning on thermostats/switches connected to them.
  5. If there’s still power, repeat steps 2 & 3.

Stay safe! Wear protective gear and use a testing device to check the electrical current before maintenance. Pressing the reset button on your furnace is like resetting life!

Locate the limit switch and reset it

Resetting the limit switch can fix furnace issues. Here’s how:

  1. Turn off power through the circuit breaker or switch
  2. Look for the limit switch in the blower compartment – it has a red button in the center
  3. Check other parts of the furnace for any problems or debris
  4. Press & hold the red button for 3-5 seconds
  5. Turn back on the power & watch to make sure all heating components are working
  6. Check circuit breakers of other electrical systems that use the same circuits as the furnace

Also, remember to replace or clean air purifying filters in your furnace regularly for proper airflow.

Clean the air filter and check for other problems

Keep your furnace working well! It’s easy – just clean the air filter and inspect for any issues. Ignoring them can cause costly repairs. Follow these steps:

1.Cut off the power.
2.Find the filter – it’s usually near the bottom of the furnace.
3.Remove and clean it. Vacuum or use soap and water.
4.Inspect for damage – check belts and components for cracks or rust.
5.Put it back, close the panels, and reset.

Remember: clean or replace the air filters every 1-3 months. Regular maintenance extends lifespan and boosts efficiency. And don’t worry, resetting the furnace won’t make your house too hot. Unless it does – then you save money on the spa bill!

Operating the Furnace after Reset

Operating Your Furnace Efficiently After Reset

Resetting your furnace limit switch can help resolve issues with your heating system, but it is important to know how to operate it effectively after resetting.

Here is a 5-step guide for efficiently operating your furnace after a reset:

  1. Make sure that the power is on. Check your thermostat and make sure that it is in the automatic mode for heating. If it is not, set it to automatic mode.
  2. Wait for your furnace to start. If it does not start automatically, you may need to turn on your furnace control panel. Look for the heating duct and make sure that warm air is flowing through the vents.
  3. Check the temperature. Once your furnace has started, check the temperature of the air coming out of the vents. Your furnace should be heating the air to at least 100 degrees Fahrenheit.
  4. Check the airflow. Make sure that the blower is running and that there is good airflow coming from the vents.
  5. Check the furnace for any issues. Ensure the flame sensor rod, air filter, vent, and plenum are all intact. If there are any problems, contact an HVAC technician for heating service or heating repair.

It is important to note that the above steps may vary depending on your furnace model and the unique problems you may face. If you are unsure how to operate your furnace after it is reset, refer to your furnace’s user manual.

In case you are still having trouble with your furnace, here is a unique detail: check the high-limit switch. This middle component of the furnace may trip during low temperatures, causing the furnace to lockout mode, which can result in cold air blowing out instead of warm air.

Finally, a true story of a homeowner in San Bernardino, CA who experienced a furnace problem that was causing them discomfort in their home. They tried several home hacks to reset the furnace limit switch on their own but were unsuccessful. 

They eventually contacted a heating service for help, and a repair technician was able to fix the problem, allowing the homeowner to fully enjoy their property once again.

Let’s put your furnace to the test because proper airflow is the key to a warm and cozy nest.

Testing for proper airflow

Maximizing furnace airflow is key for optimal performance. You must check the airflow by measuring if it’s providing enough heat in every corner of your house. Here’s a guide on how to test the furnace’s airflow:

  1. Turn off the power – Disconnect your furnace by turning off the circuit breaker or unplugging it.
  2. Remove filters – Take out any air filters in the system that may interfere with airflow.
  3. Check ductwork – Look at all ducts for dirt and debris that could reduce airflow or cause blockages.
  4. Run the fan motor – Make sure there are no obstructions. Then switch on the furnace’s blower motor.
  5. Record vents’ measurements – Use an anemometer at each vent and record measurements (Cubic feet per minute). Compare with manufacturer specs.
  6. Test sensor readings – Cross-check the readings from your thermostat with those from an anemometer. If they don’t match, call an HVAC expert.

Testing for proper airflow ensures even temperature distribution throughout the house and maximum efficiency from your furnace. Inadequate flow leads to higher energy bills – so ensuring optimal performance is important.

I faced uneven heating in my children’s room despite adequate heat in other rooms. I figured out a clogged HVAC filter was blocking warm air. Cleaning the filter solved the issue, improving heating output and airflow, and keeping my home cozy.

Now you can recline and let your furnace work automatically – just make sure it doesn’t get ideas of its own.

Re-engaging the furnace in automatic mode

Resetting a furnace is important. Follow these steps to re-engage it in automatic mode:

  1. Open all vents and registers.
  2. Set the thermostat to the desired temperature and switch to “Heat” mode.
  3. The furnace should turn on and begin heating. If not, check the settings and call a professional.

After following these steps, the furnace is in automatic mode. Look after your furnace like health – neglect can lead to costly repairs. Schedule professional check-ups regularly. This will increase longevity and ensure warmth during cold months.

Guidelines for Furnace Maintenance

As a homeowner, maintaining your furnace can save you money in the long run. Here is a simple guide to keep your furnace in top shape throughout the year.

  1. Replace your furnace filter regularly. Dirty filters can cause the furnace to work harder and collect more dust and debris, leading to potential problems and inefficiencies.
  2. Inspect the blower, vents, and heating ducts for any blockages or damage. Ensuring proper airflow can improve heating efficiency and prevent overheating issues.
  3. Check the flame sensor rod regularly. If it’s dirty, it may not detect the flame, leading to furnace lockout mode. Clean it gently with a soft cloth and ensure it’s aligned properly.
  4. Locate and test the limit switch. If the furnace overheats, the switch will shut off the burner and ignition to prevent damage. Check the high and low-temperature settings and reset them if needed.
  5. Check the user manual or contact a heating service or repair technician for additional help or instructions if problems persist.

It’s also important to note that not all furnaces are the same. Be sure to understand your specific model’s requirements and follow instructions accordingly.

Fun fact: According to a study done by HomeAdvisor, the average cost of a furnace repair in San Bernardino, CA, ranges from $150-$450.

If you want your furnace to breathe easy, give its vents, plenum, and blower some regular TLC – or else it’ll be feeling a little suffocated.

Regular cleaning of vents, plenum, and blower

Tidying airflow systems such as vents, plenum, and blower helps to elevate the effectiveness of furnace upkeep.

  • Vents should be scrubbed regularly to get rid of dirt and dust.
  • Cleaning plenums eliminates clogs that can diminish the airflow in your heating equipment.
  • The blower must also be cleaned to remove debris that could cause harm or inefficiency.

To keep the furnace performance in top shape, it’s essential to clean all related parts such as filters and upgrades regularly.

If furnace maintenance is neglected, homeowners can run into problems with their HVAC systems. For instance, one homeowner had gone without yearly checks and found his blower motor had failed. Repairs were expensive and he had to have an overhaul.

Want your furnace to stay in step with you when it comes to temperature? Better inspect it and steer clear of any icy glares.

Checking the temperature and making sure it matches the set point

For the best performance of your furnace, monitor and make sure the temperature matches your set point. Here are five steps to check and match temperatures:

  1. Find the thermostat and set your preferred temperature.
  2. Wait 15-20 minutes for the temperature to stabilize.
  3. Measure the temperature near the furnace with a thermometer.
  4. Compare the measured temp to the set point on the thermostat.
  5. If they don’t match, check air filters, call a professional, or do maintenance.

Be careful of heat sources or drafts near windows/doors, as they can affect accuracy. Set the thermostat to make your family comfortable. 

Pro tip: Install a programmable thermostat with more accurate sensors. Don’t wait till your furnace breaks down before getting help; that’s like waiting for a heart attack!

When to Contact a Heating Service or Heating Repair Technician

As a homeowner, it is important to know when to seek professional help for your heating system. If you are experiencing recurring problems with your furnace or limit switch, it may be time to contact a heating service or repair technician.

When the furnace lockout problem persists, and you have tried resetting the limit switch, cleaning the flame sensor, checking the air filter, and inspecting the heating duct, it is time to call in a professional.

A heating technician can provide valuable insights into the problem. You may discover that a faulty component is causing your furnace to stop working, or that low temperatures in your home are due to a malfunctioning blower. Whatever the issue may be, a qualified technician can diagnose the problem and provide the necessary repairs.

In fact, I had to call a heating repair technician when my furnace stopped producing heat altogether. No matter what I did, the furnace refused to turn on and I was left in the cold for some time. The technician, after examining the furnace, found the problem to be with a faulty controller, which was eventually replaced.

Remember, if you are unsure about how to reset a furnace limit switch or any other heating system components, reach out to a professional for assistance. Your property is highly valuable, and trying to fix heating problems that are beyond your expertise can lead to severe consequences.

When my furnace lockout happens more often than my ex texts me, it’s time to reset the limit switch.

When furnace lockout happens frequently

Repeated furnace lockouts can cause much frustration and dissatisfaction. If this is happening to your heating system, it’s time to call in the experts! Ignoring the issue will just lead to bigger expenses later, and even safety risks.

A heating repair technician can find the root cause of the problem and offer solutions and maintenance tips. Scheduling regular maintenance for the furnace is a must. It can detect smaller faults before they become irreversible and stop you from overspending.

A client experienced frequent lockouts, even when not at home. A professional from a reliable heating service company found corrosion in the gas control valve assembly. Replacing this during the annual preventative maintenance program solved the issue for good.

When there are other problems with the furnace components

When furnace parts malfunction, problems can arise. To avoid discomfort, contact a heating repair technician. Dirty filters can cause overheating and damage to other internal components. Address this quickly with professional help.

Strange noises such as rattling and banging from your furnace should not be ignored. A technician should diagnose this early to prevent costlier problems. Cleaning and maintenance by a professional is important – DIY fixes should be avoided as they can make things worse.

Replace air filters every few months to keep your furnace running smoothly and to avoid strain on its components. With proper maintenance, you can keep your heating system operating efficiently without unexpected breakdowns. Get a heating service technician to control the temperature inside, no matter what it’s like outside!


1. What is a furnace limit switch?

A furnace limit switch is a safety device that monitors the temperature inside the furnace and shuts off the burner if it detects a temperature exceeding a certain limit.

2. Why would I need to reset the furnace limit switch?

You may need to reset the furnace limit switch if it has tripped due to overheating or other issues, causing the furnace to shut down.

3. How do I know if the furnace limit switch has tripped?

If your furnace is not producing heat and the blower fan is continuously running, it is likely that the furnace limit switch has tripped.

4. How do I locate the furnace limit switch?

The furnace limit switch is typically located near the heat exchanger or the blower compartment. Consult your furnace’s manual or contact a professional for specific instructions.

5. How do I reset the furnace limit switch?

To reset the furnace limit switch, locate the switch and press the reset button. If there is no reset button, you may need to turn off the furnace’s power supply for a few minutes and then turn it back on.

6. Can I reset the furnace limit switch myself?

Yes, you can reset the furnace limit switch yourself. However, if the switch keeps tripping frequently, it may indicate a more significant issue that requires professional attention.

7. What causes the furnace limit switch to trip?

The furnace limit switch can trip due to various reasons, including blocked air filters, dirty blower fans, malfunctioning thermostats, or restricted airflow.

8. How often should I reset the furnace limit switch?

Ideally, you should not have to reset the furnace limit switch frequently. If you find yourself resetting it often, it is recommended to have your furnace inspected by a professional.

9. Can I bypass the furnace limit switch?

Bypassing the furnace limit switch is not recommended as it compromises the safety of the furnace. The switch is designed to protect against overheating and potential fire hazards.

10. What should I do if the furnace limit switch keeps tripping?

If the furnace limit switch keeps tripping, it is best to contact a professional HVAC technician to diagnose and fix the underlying issue causing the switch to trip.


In addressing the information on resetting a furnace limit switch, it is important to note that this procedure should only be carried out by trained HVAC technicians. Proper instructions can be found in the user manual or by contacting a heating service or repair provider. It is also critical to identify the root problem causing the lockout mode, which could be a blocked filter, a faulty flame sensor, or low airflow. In addition, regular maintenance of the furnace, including cleaning the vents, plenum, and blower, is essential to prevent future lockouts. For any heating furnace problems, it is best to seek professional help.

In examining the steps provided, a vital component not mentioned is the high-limit switch. This switch is responsible for shutting down the furnace when temperatures exceed 200 degrees Fahrenheit to prevent damage or fire. The switch is usually located in the middle of the furnace, and if tripped, it should be reset manually. However, if it trips frequently, it indicates an underlying problem that needs urgent attention.

It is essential to note that furnaces operate in automatic mode, meaning the controller turns on the fan once the furnace is heated to the set temperature. If cold air is flowing through the vents, it could be a sign of a malfunctioning fan or heating duct. Therefore, it is crucial to inspect all the furnace components, including the flame sensor rod, to ensure they are working correctly.