Sounds like a rich mixture -- gas pressure too high, orifice too big, holes
in side of burner tube blocked somehow.  But--that would show at least a
yellow tip to the flame.  I can't think of another way to get carbon
deposits other than a rich mixture, though.  Unless you're burning up
successive members of the wasp colony that built a nest in the flue...

The blowing out is from an air leak somewhere in the intake/flue loop,
usually at the vent fitting, or maybe the drain cap on the inside isn't
tight.  Put the silicone to her...the O-rings that seal the corrugated
tubes to the vent fitting leak sometimes, RTV will cure it.  And you need a
good seal to the side of the van, too.  The fitting has to sit almost
exactly right before you put the screws in, or it will distort the panel
and leak.  RTV can be useful here too, but the main tool is a broomstick
shoved into the flue so you can get some leverage and line everything up
correctly.

david

At 08:28 PM 5/22/2002, Karl M wrote:
>Before I left for a campout last weekend, I cleaned the burner in my
>Dometic, and found granules of carbon lying in the enclosure. The flame
>visible in the little sight glass was reddish in colour before I cleaned it,
>and after was blue again. The pilot indicator LED was brighter too. Well,
>today I noticed the LED dimming again, ad sure enough, the flame looked
>reddish again. Blew through the tube with compressed air, and it's blue
>again! Question: What could be causing the carbon buildup? Pressure too
>high, too low? The fridge seems to cool ok, but then it is only 70 here.
>Another symptom: lately: the flame will blow out while driving, it never did
>in the past. I'm headed out to another campout, please pmail me if you have
>any ideas. Thanks!

--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"