Lennox Furnace Troubleshooting: Common Problems and Solutions

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Last updated: 
April 30, 2024

Lennox Furnace Troubleshooting Guide (2024 Update)

Lennox furnaces, although known for their quality , can encounter issues due to normal wear and tear or lack of regular maintenance. This guide will help you identify and potentially resolve common problems.

Common Issues

  1. Furnace won't start: Possible causes include a malfunctioning thermostat, a tripped circuit, or a faulty control board .
  2. Furnace not heating: Low thermostat settings, a failed igniter, or a dirty or faulty pressure switch can prevent the furnace from producing heat .
  3. Furnace won't stay on: A defective control board, pressure switch, or flame sensor may cause the furnace to shut off shortly after starting .

Tools Required

  1. 4-in-1 screwdriver for removing furnace covers and panels .
  2. Flashlight for viewing the furnace area.
  3. Multimeter for checking voltage, current, and resistance .

Troubleshooting Steps

  1. Check the thermostat: Ensure it is on and set to the correct temperature. Replace batteries if necessary .
  2. Check the power: Verify that the circuit breaker is not tripped and that the furnace switch is on .
  3. Check the air filters: Replace dirty disposable filters every three months .
  4. Check the pilot light: If out, follow the owner's manual instructions to relight it. Clean the pilot light housing if needed .


Due to the potential dangers of working with gas and fire, it is best to contact a professional HVAC technician for repairs if you are not comfortable performing troubleshooting tasks . Some repairs, such as replacing the gas valve, should always be left to professionals to avoid damage to the part or the system .


While Lennox furnace troubleshooting can be done independently in some cases, it is essential to prioritize safety and recognize when professional assistance is necessary. Understanding your furnace and its components can help you identify issues more easily and determine the best course of action.


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  5. Lennox. (2024). Furnace Maintenance Guide. Retrieved from
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