How to Check the Ignitor
A gas dryer blows air through a burner assembly to heat the air. The burner assembly consists essentially of a gas valve, ignitor and a flame sensor. If any part of the burner assembly malfunctions, the result will be low or no heat and slow drying of the clothes.
There are two common styles of ignitors, glow ignitors and spark ignitors. The ignitor ignites the gas either by heating up and glowing, or by sparking. If the ignitor fails, the dryer will not heat.
The easiest way to check the ignitor is to observe it. Remove the small access panel in front, select a high temperature setting and start the dryer. Watch the burner assembly, shortly after starting the dryer the ignitor should begin to glow or spark. If you see it glow or spark, then the ignitor is working.
If the ignitor did not appear to function and it is the spark type, it may be out of adjustment which generally requires professional service or it may require replacement. If the ignitor is the glow type, you can test it for resistance with a multitester.
The ignitor has two wires connected to it. Label the wires and connections so that you can properly reconnect them later. The wires are connected with slip on connectors. Firmly pull the connectors off of the terminals (do not pull on the wire itself). You may need to use a pair of needle-nose pliers to remove the connectors. Inspect the connectors and the terminals for corrosion. If either is corroded they should be cleaned or replaced.
Set the multitester to the ohms setting X1. Touch one probe to each terminal. You should get a reading anywhere between 50 and 600 ohms. If you get a reading of zero or infinity, the ignitor is definitely bad and will need to be replaced.