Lennox Furnace Troubleshooting: No Heat

Furnace Troubleshooting Top 10 Furnace Problems DIY Easy Fix
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During the chilly winter months, a malfunctioning furnace can be a major inconvenience. If your Lennox furnace is not providing heat, it’s essential to troubleshoot the issue and get it fixed promptly. In this article, we will guide you through some common troubleshooting steps to help you identify and resolve the problem.

Check the Thermostat

The first step in troubleshooting a Lennox furnace with no heat is to check the thermostat. Ensure that it is set to the desired temperature and that the mode is set to ‘heat.’ If the thermostat is battery-powered, replace the batteries. If the issue persists, move on to the next step.

Inspect the Air Filter

A clogged or dirty air filter can restrict airflow and cause the furnace to shut off or not produce enough heat. Locate the air filter in your Lennox furnace and inspect it for dirt and debris. If it appears dirty, replace it with a new one. Regularly changing the air filter every few months can prevent future issues.

Verify the Gas Supply

Ensure that the gas supply to the furnace is turned on. If you have a natural gas furnace, check the gas valve near the furnace to ensure it is in the ‘on’ position. If you have a propane furnace, ensure that the propane tank has an adequate supply. If the gas supply is not the issue, proceed to the next step.

Reset the Furnace

Some Lennox furnaces have a reset button on the control panel. Locate the button and press it to reset the furnace. Wait for a few minutes to see if the furnace kicks back on. If it doesn’t, proceed to the next step.

Check the Circuit Breaker

If the circuit breaker that controls the furnace has tripped, it can cause the furnace to lose power. Locate the circuit breaker panel and check if the breaker for the furnace is in the ‘off’ position. If it has tripped, switch it back to the ‘on’ position. If the breaker continues to trip, contact a professional technician.

Inspect the Ignition System

Some Lennox furnaces have an electronic ignition system. If your furnace has this feature, check if the igniter is functioning correctly. You can do this by visually inspecting the igniter for any signs of damage or wear. If you notice any issues, it’s best to call a professional to replace the faulty component.

Check the Pilot Light

If your Lennox furnace has a pilot light, make sure it is lit. If it has gone out, follow the manufacturer’s instructions to relight it. If the pilot light does not stay lit, there may be an issue with the thermocouple or gas valve, and it’s advisable to seek professional help.

Inspect the Blower Motor

A malfunctioning blower motor can prevent the furnace from distributing heat effectively. Listen for any unusual noises coming from the blower motor. If it’s not running or making strange sounds, contact a professional technician to inspect and repair it.

Call a Professional Technician

If you have tried the troubleshooting steps mentioned above and your Lennox furnace still does not produce heat, it’s time to call a professional HVAC technician. They have the expertise and tools to diagnose and repair complex issues, ensuring that your furnace operates efficiently and keeps your home warm.


Troubleshooting a Lennox furnace that is not producing heat can be a challenging task, but by following these steps, you can identify and resolve many common issues. Remember to prioritize safety and consult a professional technician if needed. Stay warm and comfortable throughout the winter season with a properly functioning Lennox furnace!