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.