The Whirlpool WP3391902 Dryer Switch Lid Door is a small but crucial safety component in your dryer. It serves as a guard next to the door frame, making sure the dryer only runs when the door is shut firmly. The dryer's control board receives a signal from the switch itself when the door closes thanks to a mechanism in the switch. The control board is informed by this green light on the switch that it is okay to start the drying cycle. A malfunctioning WP3391902 switch may result in a number of annoying issues. For example, your dryer may not turn on at all or may turn off in the middle of the cycle without warning.