Furnace Limit Switch Reset

When it comes to ensuring your home stays warm and cozy during the colder months, your furnace plays a pivotal role. One important component of your furnace system is the limit switch. If you’ve ever wondered about furnace limit switch reset, you’re in the right place. In this comprehensive guide, we’ll delve into what a furnace limit switch is, why it might need resetting, and how to do it safely.

What Is a Furnace Limit Switch?


Resetting the furnace limit switch should not be your first course of action when dealing with heating issues. However, there are situations where it might be necessary:

  • Tripped Switch: If the limit switch has tripped due to overheating, it will need to be reset once the furnace has cooled down.
  • System Malfunction: Sometimes, a malfunction in the furnace can cause the limit switch to trip unnecessarily. Resetting it can be a temporary solution while you investigate the underlying issue.

How to Reset the Furnace Limit Switch Safely

Before attempting to reset the furnace limit switch, ensure you follow these safety precautions:

  • Turn Off the Power: Safety always comes first. Turn off the power supply to your furnace from the circuit breaker to prevent electrical accidents.
  • Let It Cool: Give your furnace time to cool down. You should never attempt to reset the limit switch while the furnace is hot.

Now, let’s proceed with the steps to reset the limit switch:

  1. Locate the Limit Switch: The limit switch is typically located near the burner chamber. It’s a small device with wires connected to it.
  2. Identify the Reset Button: Some limit switches have a reset button. If yours does, simply press it to reset the switch.
  3. Manual Reset (If No Button): If your limit switch doesn’t have a reset button, you can perform a manual reset. Carefully slide the dial or lever on the switch back to its original position. This should reset the switch.
  4. Turn the Power Back On: Once you’ve reset the limit switch, turn the power supply back on from the circuit breaker.

Common Causes of Tripped Limit Switches

Understanding why your limit switch tripped in the first place can help you prevent it from happening again. Here are some common causes:

  • Clogged Air Filters: A dirty or clogged air filter restricts airflow, causing the furnace to overheat. Regularly changing your air filters can prevent this issue.
  • Blocked Vents: Blocked or closed vents can lead to insufficient airflow, resulting in overheating.
  • Malfunctioning Blower Motor: If the blower motor isn’t working correctly, the furnace may not circulate air properly, causing overheating.
  • Dirty Heat Exchanger: Over time, a dirty heat exchanger can impede heat transfer and lead to overheating.

Preventive Maintenance for a Healthy Furnace

Maintaining your furnace is key to preventing frequent limit switch tripping and ensuring efficient operation. Here are some preventive maintenance tips:

  • Regular Inspections: Schedule annual inspections by a professional HVAC technician. They can identify and address issues before they lead to limit switch problems.
  • Change Air Filters: Check and change your air filters regularly, ideally every 1 to 3 months. This simple task can significantly improve airflow and prevent overheating.
  • Clean Vents and Ducts: Keep vents and ducts clean and unobstructed. Dust, debris, or blockages can restrict airflow and strain your furnace.
  • Inspect the Heat Exchanger: Have your technician inspect and clean the heat exchanger during routine maintenance visits.
  • Check the Blower Motor: Ensure the blower motor is in good working condition. If you notice any unusual noises or reduced airflow, contact a professional for inspection and repair.

When to Seek Professional Help

While resetting the limit switch can sometimes resolve immediate issues, there are situations where you should seek professional assistance:

  • Frequent Tripping: If your limit switch keeps tripping, it’s a sign of an underlying problem that requires expert diagnosis and repair.
  • No Heat: If resetting the limit switch doesn’t restore heat to your home, there could be a more significant issue with your furnace that needs immediate attention.
  • Unusual Noises or Smells: Unusual sounds, odors, or other abnormal furnace behavior should be investigated by a professional.
  • Gas Smell: If you ever detect a gas smell near your furnace, turn off the gas supply immediately and contact a professional technician and your gas company.

Common Furnace Limit Switch Reset Methods

Method NumberMethod DescriptionTools RequiredSteps to ResetSafety Precautions
1Power ResetNone1. Turn off power to furnace. 2. Wait a few minutes. 3. Turn the power back on.Ensure power is completely off.
2Manual ResetScrewdriver1. Locate the limit switch. 2. Press the reset button.Ensure the switch is not damaged.
3Temperature Adjustment ResetScrewdriver, Temperature gauge1. Adjust the temperature settings.Monitor the furnace’s operation.
4Flame Sensor Cleaning ResetScrewdriver, Cleaning brush1. Turn off power to furnace. 2. Remove and clean the flame sensor.Handle the sensor carefully.
5Circuit Board ResetScrewdriver, Pliers1. Turn off power to furnace. 2. Reset the circuit board.Consult a professional if unsure.

Furnace Limit Switch Types

Switch TypeFunctionLocationCommon IssuesMaintenance Tips
Manual ResetRequires manual intervention to reset.Near the burnersOften gets stuck due to dirt.Periodic cleaning needed.
Automatic ResetResets automatically once temperature is within limits.Inside the furnace casingCan malfunction over time.Regular inspection advised.
Rollout SwitchShuts off the furnace if flames rollout.Near the burnersActivates due to flame irregularities.Ensure proper combustion.
Fan Limit SwitchControls the blower fan operation.Inside the furnace casingMay wear out or accumulate dirt.Lubricate moving parts.
High-Limit SwitchShuts off the furnace if it overheats.Near the heat exchangerTrips during overheating conditions.Check for proper ventilation.

Troubleshooting Furnace Limit Switch Issues

Issue DescriptionPossible CausesTroubleshooting Steps
Furnace not heatingLimit switch tripped, no power, faulty thermostat1. Check limit switch. 2. Verify power supply. 3. Test thermostat.
Frequent limit switch tripsRestricted airflow, dirty filter, faulty switch1. Replace dirty filter. 2. Ensure proper ventilation. 3. Replace switch if needed.
Continuous fan operationFaulty limit switch, thermostat issue1. Check limit switch operation. 2. Inspect thermostat settings.
Inconsistent heatingClogged air ducts, thermostat issues1. Clean air ducts. 2. Calibrate or replace thermostat.

Limit Switch Reset Frequency

MonthlyRecommended preventive maintenance.
AnnuallyRegular maintenance for most systems.
As NeededReset when issues or trips occur.
NeverSome systems have automatic resets.
ProfessionalAlways consult a technician for safety.

Safety Tips for Furnace Limit Switch Reset

Safety TipDescription
Turn off powerAlways disconnect power before resetting.
Wear safety gearUse gloves and eye protection if necessary.
Follow manualsRefer to furnace and switch manuals for guidance.
Regular maintenancePrevent issues with routine checks and cleaning.
Call a professionalIf unsure, seek the help of a certified technician.


Resetting the furnace limit switch is a straightforward task that can be performed safely when necessary. However, it’s crucial to prioritize preventive maintenance and address any underlying issues to minimize the risk of frequent limit switch tripping.

Remember, your furnace’s reliability and safety depend on regular maintenance and professional inspections. By following the guidelines in this guide and knowing when to seek professional help, you can keep your home warm, comfortable, and safe during the cold seasons. If you encounter recurring issues with your furnace, don’t hesitate to contact a qualified HVAC technician to ensure the proper functioning of your heating system.

Furnace Limit Switch Reset


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