2018 Winnebago Vista Water Heater Blows Out During Ignition

Very simple. The flame/heat round internal tube that runs from the flame in and around and out the exhaust has a blockage/partial blockage. THIS is the cause of flame back or blow out when door is closed. BAD DEALER. Period. You remove the burner and the upper exhaust cover and use a water hose to wash out and a spring type snake to clean out the blockage. The standard test BEFORE you do this is to run a Golf ball down that tube. If it does not come out you have a blockage. You CANNOT see this blockage. Doug