I've been bench testing my Dometic for several days and have found something
very interesting.

The problem has been that it is often very hard to light and also sometimes
spontaneously goes out, even after hours or days of running successfully and
when all is stable and the van is not moving.  Actually, it lights easily,
but only stays lit a few seconds.  Then I must pump a whole lot and can
light it again, only to have it go out again in a few seconds.

ON the bench, I have been running it with the vent parts E and F installed
(see drawing at http://www.takingflight.net/images/fluevent.pdf  ) and all
runs fine.  I have mounted a mirror so that I can clearly see the flame
through the little window in the combustion box.  Flame is strong and
steady.  I add part C and all is still well.  Then I add the outer vent,
part B, and within seconds, the flame becomes unsteady and I can hear a
distinct sound of the flame fluttering.  It was silent before.  Then, within
10 seconds, it consistently goes out.

I also tried adding only the outer vent, part B, leaving C uninstalled, and
the flame remained lit.

I must add that the vent parts are not damaged or distorted and, as far as I
can tell, the chimney and intake pipe are also in good condition.  I have
done the cork and blow test and ascertained that the combustion system is
very nearly perfectly sealed, enough to make your cheeks bulge when you blow
on it.

Only after the whole system gets good and hot will it tolerate the outer
vent parts B and C being installed and still run stably.

I have measured the pressure, right at what it should be..11" inches of
water.

Any idea what is causing it to blow out?

Paul Chubbuck

Fort Collins