By visual observation, I determined that the gas burner would light once then not re-light. I purchased a flame sensor and a gas valve coil kit.I believe the flame sensor failed, but purchased both parts due to the dryer being purchased used. The repair was easy, everything was easily accessible with only the front panel removed, the total repair time was 20 minutes start to finish. The tools needed were basic homeowners tools, a Phillips Screwdriver and a 1/4" nut driver, a 6-way screwdriver is actually what I used.