Originally Posted by cpaharley2008
The purpose of the cover is to keep the combustion area warmer, not to prevent snow intrusion. The absorption refer needs some contrast in temperature to operate, something that is hard to do in real cold regions.
If the cover were only over the burner housing that would make more sense, to allow the burner to get the working fluid high enough for the cycle to work. Airflow through the coils on the back of the refrigerator is required because that part needs to be cooler (that difference in temperature), and at the very least air intake and exhaust is needed for the burner if running on propane. All of the images that come up in a Google search for "Dometic winter cover
" show covers that block the vents.
A Dometic catalog
confirms that they cover the vents, says that they are for low-temperature operation... and provides no indication of how the exhaust is handled. It appears that they have small openings lined up with the burner intake and exhaust which are just sufficient.
Winter sets for single- and double-door models:
WA 120 / 130 are available as replacement covers. EWS 300
enhances your fridge’s insulation values and ensures
maximum performance even at ambient temperatures
I have found in low temperatures (-10 C and lower) - with a larger and different-brand trailer - that the refrigerator section stays at the desired temperature but the freezer isn't cold enough. The cooling action required to keep the refrigerator at 4 C (40 F) isn't enough to keep the freezer well below freezing.
Thousands of people in North America use their RVs with this type of refrigerator in sub-freezing temperatures every year. If the covers work, and are not offered here, it suggests to me that Dometic has had difficulty with some sort of regulatory approval.
This has been educational!