Sporatic burning water heater

[Pullingtin]

Or I could say erratic burning! I have an Atwood Model G6A - 8E water heater in a 2008 Safari. When the bathroom switch is turned on - it ignites immediately but then "flames out". The igniter fires immediately and after a varying number of attempts the heater re-ignites. However it will in seconds to minutes shutdown again and go through the same re-igniting procedure. While it is running the burner "spits" (not a solid burn). I have cleaned the unit and can't find any obstruction in the gas nozzle or burner tube. I've tried operation with the door open but it doesn't change anything. With time and patience (and uncountable restarts) it will ultimately heat the water and shut off as required.

[rmkrum]

Blow some air through the tube (flue) that goes through the tank, or run a brush up it. Sometimes bugs build a nest in there, especially Mud Dauber wasps. If its partially blocked it may not burn right.

Wear eye protection if you blow air through it....stuff flies out at high velocity...

Check the position of the flame sensor if you have electronic ignition. If its not in the right part of the flame it can act weird.