Dometic Diagnosticians, for your viewing pleasure...I present pictures
of my Dometic 182b running from a BBQ LPG tank with the flame box
opened.

High Flow (thermostat on max):  http://xochi.com/vanagon/dometic/high.JPG
Low  Flow (thermostat on zero): http://xochi.com/vanagon/dometic/low.JPG
Top angle, looking down: http://xochi.com/vanagon/dometic/lookingDown.JPG
Closeup, showing the piezo electrode glowing red:  http://xochi.com/vanagon/dometic/closeup.JPG

The flame doesn't actually look bad to me, thought I can't judge the
flame size.  Looking directly from the side, eye level with the top
edge of the box, on high the visible blue part of the flame gets about
1/4 inch above the edge of the box.

The electrode glowing red is new to me, and I'm wondering if it's
because (A) I lightly sanded off the black gunk and it's busy re-
oxidizing, or (B) it's in the wrong position (see the top angle shot)

Given that this fridge works wonderfully on 120VAC (33F interior when
run overnight) -- If these flame sizes are normal, where do I go next?

* Fuel: perhaps the flame looks OK because of a different pressure
regulator on the BBQ tank?
* Air:  perhaps the flame looks OK because it's getting more air --
could my vent or flue be clogged (the flue/vent pipes seem to flow
just fine when I blow through it, and doesn't seem to leak when i plug
one end and blow on the other)
* Heat conduction:  perhaps the flue is no longer connected well to
the coolant tube so the heat transfer is not happening?   Could rust
accumulation inside the flue cause this?  Can the tube separate or
break?

Ideas suggestions gladly taken... I can get more pictures if needed.