First, this test can be dangerous if you are not familiar with electricity. Don’t attempt if you are not experienced- see a professional!

Remove the spark plug wire from the spark plug. With the heater running, stay clear of the fan blade, and using a good set of insulated pliers hold the plug wire ¼” from the metal body of the heater. Spark should jump the gap between the plug wire and the heater.

If NO, use a voltmeter to confirm that there is 115v ac going into the Ignition Device from the Safety Control (reset).

If YES, there is voltage going in, but no spark, then either the Ignition Device is defective, or it is not grounded to the body of the heater.

IF NO, you have a problem with the Safety Control (reset), power cord, or wall receptacle.