Lennox Heater Not Working [Solved]

Is your Lennox heater not working? There could be any number of reasons your Lennox heating system is not working, these include:

  • Tripped circuit breaker
  • Open furnace door
  • Furnace ignition problems
  • Malfunctioning inducer motor
  • Nonfunctional gas valve assembly
  • Malfunctioning thermostat
  • Problems with gas supply
  • Malfunctioning pressure switch

lennox furnace not working
heating system set up

Also read: House Heater Not Working [8 Easy Solutions]

9 Reasons for Your Lennox Heater Not Working

In the heating season, is the time when you really need your furnace up and running. But when your heating system stops working, this can your and your loved once miserably cold. This is not just uncomfortable for your but not healthy too. Lennox heaters are among the world’s respected heaters in terms of performance and quality. But just like any other machine, they can develop issues that would prevent them from working properly.

So, what are the reasons for your Lennox furnace not working.

1)Tripped Circuit Breakers

When your heater is not working, the first thing you want to do is rule out is a tripped circuit breaker. Go to the circuit breaker box and verify that there are not tripped breakers.  For your furnace, the breakers should be labelled ‘air handler’ or FAU (forced air unit). Reset any tripped breakers. After you have checked out with breakers and your heater is still not working, go to the next step.

2) An Open Furnace Door Could Prevent a Heater from Turning On

If your Lennox heater is not turning on, it could be an open furnace door causing this problem. Furnace doors have built in switches that will turn off your furnace when they are open. If you were recently changing your air filters or checking out something with your furnace, you might have not closed the door completely.

Check the furnace door again to ensure its securely closed. Another issue caused by an open furnace door is a blank screen on a thermostat. If closing the furnace door does not solve the problem, move on to the next step.

3) Furnace Ignition Problems

If your Lennox heater is not working, the problem could be with the ignitor. An ignitor ignites the burners for combustion to take place. And combustion of gas is what heats up the air. If the ignitor is dead, it will not do its job and you won’t have heat coming into your home. You will know if your ignitor is dead if you see cracks on it. You can also test it for continuity using a multmeter.  If your ignitor has cracks, it’ll need a replacement.

There are four types of ignitors a furnace can have namely:

  1. The standing pilot: The standing pilot is common in older furnaces. This type of ignition needs you to manually light up the pilot light and it will stay on all the time.
  2. Direct spark ignitor: This type of ignition has a spark that ignites the burners. When the valve opens, the gas flows into the burners and the spark will ignite that gas right away.
  3. Intermittent Pilot: This is different from a standing pilot because this one is intermittent. It only turns on when there is a call to heat.
  4. Hot surface ignitor: This type of ignition is common in modern furnaces. When a hot surface ignitor is defective (usually when it has crack) it will not light up the burners. In this case, you’ll need to replace the ignitor to solve the problem.

Also read: Central Heat Not Working in House? [Solutions]

4) Dirty Flame Sensors

A dirty or sooty flame sensor will not do its job- to detect flames when they are present. When the burners are ignited, the flame sensor is there to detect the flames. If flames are present, gas will continue flowing into the burners. But if there are no flames present, a flame sensor will send a message to the control board to close a gas valve to prevent gas from flowing otherwise gas would leak and contaminate your home.

If a flame sensor is malfunctioning or is dirty, it won’t be able to detect flames even if there are present. This will result in the gas valve shutting and eventually turning off the combustion. A dirty or malfunctioning flame sensor can cause a furnace to short cycle.

Your can remove the flame sensor and clean it. If the problem is not sorted out after cleaning it, consider replacing your flamer sensor.

5) Malfunctioning Inducer Motor

The draft inducer motor draws air from your home into the furnace and through the heat exchanger. If the inducer motor is dead, it won’t draw air into the system and the pressure switch will sense this. If the pressure switch detects that there is no proper air flow into the furnace, it will not send any signal for the circuit control board to start the furnace.

6)Defective Pressure Switch

A pressure switch detects if there is proper air flow around the burners. If the pressure switch is not working, it won’t close the switch even when there is proper air flow coming in. This will prevent the furnace from igniting. You can know for sure if the pressure switch is defective by using a multimeter to test it for continuity and if it doesn’t have continuity, its time you replaced it with a working one.

7)Defect Gas Valve Assembly

When you switch on your furnace, the valve opens to allow gas into the burners. But if the gas valve assembly is defective, it will not open for the gas into the burners. So, your furnace will not ignite.

8)Problems with Gas Supply

If there is a problem with your gas supply, your gas furnace won’t work. Check the main gas valve on the pipe if its open. In general, if the valve handle is perpendicular with the pipe, then you know the valve is closed.

9)Thermoset Settings

Above all, make sure that your thermostat has the correct setting. Ensure that it is on. If your thermostat is a programmable one, make sure it is not on a schedule that could prevent it from turning on.

Sometimes your furnace won’t turn on if your thermostat has flat batteries. Generally speaking, batteries in your thermostat can work for about a year before  you can replace them.

Final Thought

When you are dealing with a Lennox heater not working, it can be frustratingly hard to pinpoint the real source of them problem. If you have tried out all our tips and nothing seems to be working, its best to contact HVAC professional services to come and have a look. Alternatively, you can call Lennox customer support.

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