The Dometic loves to operate while the Vanagon is being driven. If it blows
out, the exhaust vent could have a crack in it, or the gas pressure is too
low. Remove the chrome plate on the vent and plug up the inner intake vent
while you blow into the exhaust vent that sticks out the furthest of the two
vents(refrigerator turned off and cool, of course). This test will show no
leak if the exhaust system is sealed up good. Needs to be sealed good to run
while the Vanagon is on the road.

The gas regulator has an adjustment that can be moved with a screwdriver
bit. Go to yahoo and type in "manometer" to get directions on how to make
one and how to use it (EZ). This adjustment disk is spring tensioned, and
over time and ruff roads, it can unwind slightly and change the gas
pressure.  Too high or too low is not good. Got to be right on to specs
given in the manometer directions.