Ignitor Replacement, A Step By Step Guide

With our ignitor replacement guide, you can diagnose and replace your furnace ignitor. For a hvac service company to provide the part and install it, you would pay around $150. With this helpful guide you can keep most of that money! You can even watch our video to see how it is done.


**NOTE** ONLY YOU CAN ASSESS YOUR ABILITY TO PERFORM THIS TASK. THIS IS A GUIDE AND CANNOT PROVIDE ALL DETAILS FOR EVERY SITUATION. Before proceeding with replacement, you should first verify that it is the problem. You can do so by watching our video on the player below.

Types of Ignitors

The purpose of the ignitor, on your furnace, is to automatically light the gas for the pilot light or main burners. This is usually accomplished in one of two ways.

The first method is spark ignition. The ignitor is a round piece of metal with a ceramic insulator. The furnace control board supplies a high voltage to the ignitor which causes a spark that ignites the gas. There is usually another metal rod called a flame sensor which senses the flame. After the flame is sensed, the control shuts the power off to the ignitor and the sparking stops.

The other method is hot surface ignition. This is more common on newer high efficiency furnaces. This method uses a ceramic ignitor. The furnace control supplies power to the ignitor and causes the ignitor to heat up. When the ignitor is glowing bright with the heat, the gas is turned on. The gas is ignited by the heat of the ignitor. After the flame sensor senses heat, the furnace control turns the power off to the ignitor.

Ignitor Replacement, Diagnosing Problems

On spark ignition systems, it is rare for the ignitor or flame sensor to go bad. They are really just a piece of metal with a ceramic insulation mounting base. If they appear to be bad, look for a crack in the ceramic base. If you do not see a crack the ignitor or sensor is probably not defective. Sometimes they get a buildup of deposits on them which cause them not to sense the flame. Instead of replacing it, you should clean the sensor by wiping the deposits off or shining with a piece of steel wool.

On hot surface ignition systems, if the ignitor does not heat up and glow bright orange, look for a crack in the ignitor. It is usually easy to spot. If there is not a crack, the ignitor is good.


To begin the ignitor replacement, you should turn the power to the furnace off. Then you can disconnect the wire(s) that go to the ignitor. On hot surface ignition systems, the ignitor wires are usually in a plastic plug and socket. On spark ignition systems there is usually only one wire that snaps onto the ignitor or ignition module. Then you can remove the mounting screws and remove the ignitor.

You can use the numbers that are usually printed on the ignitor to find the proper replacement or there are several universal kits available.

Now, you can install the replacement ignitor with the mounting screws. Then reconnect the wire(s) and restore power to the furnace.

You should complete your ignitor replacement by observing a complete heating cycle.