lennox furnace won’t ignite

Lennox furnace won’t ignite. A Lennox furnace is responsible for supplying heat and air to your home. They are known for lasting a good long time and providing efficient service.

But, like anything else, it can get into trouble sometimes requiring repair. For one thing, there could be something wrong with the ignition system because the ignition is key when it comes to starting your furnace.

Many gas furnaces have problems with getting their pilot light going and such if the insulation has deteriorated around the burner causing the exact problem you are dealing with right now (i.e. the pilot light won’t stay lit when you turn on the switch).

Another common problem is if dirt or debris gets inside of the burner where it shouldn’t be like paper or ashes from a fireplace. This can cause your furnace not to stay lit as well.

Lennox furnace won’t ignitefurnace won't ignite

Here we will discuss some common issues and solutions for Lennox furnace won’t ignite.

Gas Line Failure

When we have a furnace that is not firing up as we would like it to, there are some quick things we can try before having to call in the factory service guy.

Make sure the gas line is turned on first. You can do this by observing the shut-off valve outside. Starting another gas-burning appliance, such as a stove, will also tell you if the gas is on and working.

If it seems like the gas line may be the issue and there’s stop-used flow then check to make sure that your furnace has more than enough fuel supply and that a clog of some sort has not formed due to debris or something blocking it for example.

Faulty Flame Sensor

The Flame Sensor detects when there is a flame present and if the sensor doesn’t detect a flame then it will shut off the gas valve to prevent the furnace from lighting.

Sometimes if anything blocks the Flame Sensor’s view of the burner, it will not detect a flame and therefore turn off the gas valve.

If this happens to be the case, unplug your furnace for 30 minutes. Then plug back in and see if it starts working again. If not, you must replace your Flame Sensor using a  screwdriver or a similar tool because this is an OEM part that requires precise handling.

Defective Control Board

The control board is an important part of a furnace as it regulates the power supply to all the components.

If it fails, for example by sending a bad voltage reading to the ignition system, this could prevent the furnace from lighting.

Gas Valve Problem

The gas valve opens to allow the gas to reach the burner. If it is faulty it will not open, thereby causing the furnace to malfunction. To determine if the gas valve is at fault, you can use a multimeter for continuity testing.

If there is no continuity in the circuit when you try testing the valve, then it’s most likely broken and needs to be replaced ASAP!

Defective Pressure Switch

The pressure switch does not work when it does not have sufficient airflow. If the pressure switch is not working either because of a fault or if you need to replace it.

One can check whether the pressure switch has a connection by using an ammeter or multimeter.

Ignition Sensor Failure

When your furnace won’t ignite, it’s usually the pilot light or ignition sensor. The thermocouple is specifically mentioned in this article because it’s likely to be the cause if you can hear your furnace clicking on but it does not fire up.

Follow these steps, and you may be able to fix a faulty or dirty ignition or sensor on your own.

First, you want to find where this part is located – typically near the burners of your furnace. Sometimes they are deep inside so if you cannot access them easily then the entire unit may need replacing by a professional.

Air Flow Issue

The furnace needs to have optimal airflow and burners working in order to keep running. The furnace draws air from side rooms and/or outside houses for efficient heating.

If the furnace is located in a utility counter or storage room that does not allow enough available space for the heat exchanger, insufficient airflow may cause the furnace door to remain open, preventing proper function of the heating system and forcing it to prematurely pump out warm air instead of keeping it inside.

Related Guides