There is a lot of information out on the web and buried within the refrigerator manuals
in the document section here on FGRV. Unfortunately most of the information available is copyrighted so I cannot post diagrams. The page http://www.rvmobile.com/Tech/Trouble/vent.htm
has some good diagrams with explanations. If that page is gone, Google "Almost good venting" and you will find more sources.
The 2 basics of good venting are good air flow over the fins and having minimum dead air spots. My fix involves the Dometic RM182B that came with my 1972 Boler
American; it was originally designed for the VW Westphalia campers. Many fridge
installations present similar problems - so my fixes might work with other trailers and fridges. If not, it should get others thinking how they can address their own unique problems and post their solutions.
The vent that was on my trailer, as purchased, is shown below. I could not open the vent door unless I removed the intake/exhaust fixture for the fridge propane
burner. The vent was ugly, bent, stuck out from the body an inch or so and really did not work the way it was intended to.
If you compare the vent to the picture below, you can see many of the problems with the original install. There is a large dead air space above the fridge
behind the stove burner that was not vented (all that is above the belly band). The upper fins really had no air flow to cool. You can see a fan that was original equipment on the bottom fins. It is controlled by a thermocouple attached to the yellow wire. I plan on installing 2 computer fans to aid in air circulation above the rear of the fridge and I am still undecided whether or not I should connect them to the original thermocouple. I am also considering a putting small fan inside the fridge itself. Opinions and comments are welcomed.
I used a stock Norcold lower side vent door added to an aluminum frame along with some sheet aluminum to close the large hole left by the previous install. This configuration will help start directing air over the fins. The large bulge you see on the back of the metal assembly is a galvanized piece of HVAC sheet metal modified from a duct elbow and used as a baffle to further direct air over the fins. I cut two holes above the belly band for exhaust vents and added some galvanized sheet metal to help direct the hot air outwards eliminating a dead spot.
I then installed two 8" x 4" Imperial RG0618 Sidewall Registers to fill the upper holes using butyl tape instead of the foam they came with. As you can see in the next picture the vent's door works in tandem with the sheet metal to help direct the hot air in a continuous flow. When the doors are closed they also prevent bugs from getting into the back of the fridge. I can block of the lower vent to totally seal off the back of the fridge when not in use or in storage.
The final touches of this project were finished while at Bolerama held at Emily in 2007. Here are before and after pictures.
You can follow the chronological restoration of our trailer here: