Product review (5 stars): If this switch is bad AND your dyer won't start read this
I determined that the switch in my whirlpool dryer was bad after watching some videos online about how to test and replace various dyer parts. I knew there was something wrong when the dryer wouldn't stop running when I opened the door but didn't realize this switch was to blame when the dyer later failed to start altogether, because I could still fiddle with the switch and get the light to go on and off. If you find yourself in this situation and still need to use your dryer you can override the bad switch by cutting it off from the lead wires and connecting two of them together with a wire nut. You will need to read the wiring diagram for your dryer to do this and be comfortable with basic electrical work. Do not attempt this with the dryer plugged in and be sure to install the replacement switch ASAP to restore the safety interlock.