Atwood Furnace Problems

On a 17 year old furnace that has Mud nests. It is the ones you CANNOT see in the burner tubes that may be the problem. I would remove the furnace and the motor and circuit board and run water thru the intake and exhaust tubes to flush out the burner chamber. You may be surprised to see what comes out. I also use a rubber mallot to gently tap the burner chamber to dislodge any nests that are hidden when running water thru. DO NOT use that 1/8 gap as gospel. A 3/16 gap is usually a better gap for spark and flame sense. ALWAYS remove the orifice over a white paper or cloth and tap on the Gas valve. debris can be inside and the force of the lp gas and flip debris up and partially clog the orifice. The white cloth lets you see anything that comes out. Doug