This is especially for Gary but anyone who has an idea or possibly has seen this symptom please do jump in. On another RV forum that I am part of a new member just posted that they bought an RV with a Suburban furnace and the first time they turned it on it blew the screen off of the exhaust port when it light. They say that it seems to cycle normally but did do that a second time later. Other than telling them not to use the furnace, does anyone have any ideas of what might be the cause. I did come up with a theory but will hold off sharing that to see what someone else can suggest. This guy needs help!