I have a Ducane gas furnace (Model-MPGA125A5). I have been experiencing problems with it lighting. Occasionaly, the vent fan would kick on, but then nothing would happen. At first, tapping on the gas head would cause the unit to fire up. The problem has become more frequent, and I have found that if I jiggle the 4 wire connector on the side of the head, that the unit would fire up.
Before I go and order a gas head, I wanted to make sure that this was where the problem was?
It a Smart gas valve and it will cost big bucks. I may check pressure switch tube and take paper clip into the bar fitting on draft motor. The flame sensor maybe dirty too but good luck cleaning it most the time I just replace it due to not breaking the glow plug.