I wish I had video of the "Belching Dragon" I worked on back in the 90's.
Lennox whisper heat with a failed proving switch for the damper, that the homeowner had tried to fix himself.
Somehow he managed to get the wires screwed around to the point that the gas valve would open at the same time the damper started to open.
Once the damper opened far enough to make its proving switch, the ignitor would start sparking.
The furnace was an upflow in a closet, and I was bent over watching the startup sequence, and failed to notice that the gas valve had gotten energized...
Use your imagination from there.
Lets just say that my first stop after that call was my barber.
