Larryjb,
I have spent considerable time troubleshooting my Norcold 3-way refrigerator on propane mode. The process involved replacing the thermocouple, the thermocouple interrupter, the red and blue wires connectiong the interrupter with the selector switch, removing and cleaning the burner (I have a new one on order), removing the selector switch back cover and cleaning/lubing all contacts, and removing (and reinstalling) the unit 3 different times. All the parts I replaced tested (minivolt/amp tester) marginal hence the reason they were replaced. At the time I opted to clean the burner slots and continue using it as long as possible. The Norcold models operate in propane mode without any additional outside power whereas the Dometic units need a DC source (
CORRECTION - only certain models require DC power to operate on propane, the ones with auto ignition). Additionally, at least on the Norcold models, it is possible to control the size of the flame thereby controlling (to some extent) the cooling temperature. Turning the temperature selector to 5 produces a larger flame while selecting 1 reduces the flame size. To be sure, the flame is never much larger than a typical gas pilot.
Your Dometic unit looks to be a bit simpler to work on. I have no experience with Dometic refrigerators but have done a bit of research. You are correct in assuming the flame should be completely blue - no yellow/orange color at any point. The cause of the yellow flame, in most cases, is a dirty burner or a burner that has enough rust to change the size of the slots. I would suggest you replace the burner before replacing other parts. The "chimney" may be difficult to remove. I would try the method suggested in this You Tube Video first:
It also gives a nice explanation of how to deal with the burner.
I hope some of the above is helpful and lets you resolve the burner flame issue.
Let us know how it goes.
Dick