Press the reset button on the heater and look through the flame observation window and check for a glow when the ignitor LED on the heater is ON. To get the best viewing angle, look through the window from the right side. The burner tube and the ignitor are located towards the left of the observation window. The glow of the ignitor should be visible through the holes in the burner tube. On a bright day, it may be necessary to block out the light to get a good view.