What really determines the overall cooling efficiency of any absorbtion type fridge is that ability for the coils in the rear cavity to exchange their heat with the ambient air flow.
Consequently, if little natural airflow is present you have to artificially provide the air flow.
If the upper vent is on the roof and the lower (intake) vent is low down on the side of the unit, natural convection takes place (draft / warm air rises and is replaced with cooler air). However, if the fridge is in a slide (as is common today), the spacing between the upper vent and the lower vent isn't all that great, consequently there is little natural convection (draft) and cooling suffers because the coils cannot rid themselves of the heat and for the thermosiphon principle to work, the warmed by the boiler fluid must be cooled off.
Consequently, a fan or two, place in the upper vent area (blowing out) or in the lower vent area (blowing up) always improves the heat exchange and makes the fridge more efficient.
Only issue with placing a fan(s) in the lower vent area is you don't want to disturb the small flame that provides heat for the boiler.
Also important is the amount of insulation around the fridge unit between the fridge itself and the framing / walls. RV manufacturers really skimp on that and the more there is, the better because an ammonia fridge, even when working properly isn't all that efficient so mitigating any cold to warm heat exchange between the fridge box and the walls is also important.
My unit, when I brought it home and took the vent covers off, was almost devoid of insulation between the fridge and the walls. I was able to stuff, almost a full roll of R12 unfaced insulation, between the fridge and the walls. Took some doing with a long wood stick and time but it's doable. Made a huge difference in the fridge getting cold quicker and maintaining the cold.
On fans, Dometic supplies some of their units with a 120mm muffin fan mounted in the upper cavity (mine had one), absolutely the cheapest fan available. A sleeve bearing model that sounded like a chainsaw when running. I replaced that with a pair of FDB (Fluid Dynamic Bearing) CPU cooling (120mm) muffin fans, 2 wire. Don't get a 3 wire fan, the 3rd wire is to allow the CPU to control fan speed and is not needed.
My unit already had a snap disc thermostat affixed to the upper condenser fin so I just wired both fans through that. It closes at 110 degrees and opens at 90, perfect for the fans. Both fans pull a bit less than 1.2 amps so I put an inline fuse (2 amp) in the circuit as well.
I want the fans to run automatically, less switches for me, the better.
Another good way to enhance the cooling is install a fan inside the fridge to circulate the cold. They are available on Flea bay pretty cheap. Cold air movement inside is just as important as air movement over the coils in the back of the unit. In my case, I try to keep the fridge full and open the door as little as possible.
I will say that when this one ever expires (if it ever does), I'll replace it with a Danfoss Compressor fridge which is much more efficient than a conventional residential type compressor fridge (draws much less power).
We have a portable Dometic fridge / freezer right now and it's a wonderful unit to keep in the truck to keep pop cold and make ice cubes in or keep ice cream rock hard.
2015 Backpack SS1500
1997 Ford 7.3 OBS 4x4 CC LB
