My 6 Gallon Atwood H.W.H. is ORIGINAL in my 93 and it's still going strong with the original ignitor board.
Every season I pull the burner assembly and take a brush to the heat exchanger tube followed by compressed air (watch the eyes).
I take a scotch bright to the ignighter/flame sensor and gap at 1/8" Inspect the insulator and make sure it's clean with no cracks. Assemble the burner making sure the flame sensor is in the path of the flame.
I adjust the air mixture as stated above, Just a tad of orange flame. Should have a low rumble, if adjusted too lean it will sound like a blast furnace.
My flame sensor is in the path of the flame & about 1/8" of the tip is cherry red when burning.
Could be the flame sensor OR possibly the board. Some places can test the ignightor board.
Keep us posted.
