When I turned on the lower lights, I heard a loud pop. One blub was burned out. replaced with new. Still no light or Exhust Vent. It doesn't work either. Have removed from wall and removed housing. I do not see anything blown of burned. Replaced 250v 20 amp fuse, still no lights or vent. The unit runs just fine except for vent and lights. Can you tell me which part do I need to replace? This a Dometic Microwave on my Everest Fifth Wheel.