Had the (unwelcome) opportunity to research refrigeration operation recently on my first trip in my 2552 since being parked for Covid all last year. Fired everything off at home a couple days early and everything worked fine--generator genned, water pump pumped, fridge cooled, water heater heated. Only after getting on the road and switching the fridge to propane did I note my slide out mounted fridge temp steadily increasing. Start/restart didn't help, so when the temp got to unusable levels, I stopped and fired the generator; fridge cooled back down immediately, so I kept the generator running until I made it to my son's house in Fort Collins, and plugged into his 50-amp service; the fridge continued to work great on electric power.
With no prior experience on the fridge, I started with the owner's manual and progressed to online research; I looked at a lot of forum entries and YouTube videos. The fridge would readily fire up on propane, and the flame looked kind of erratic but maybe OK?, but it just wouldn't cool. To make a long story short, what I finally found was a dirt dauber mud-ball inside the exhaust vent pipe that didn't have it completely obstructed but restricted the heat flow enough that it wasn't heating the ammonia/water mixture sufficiently in the boiler to allow the fridge to cool when fired on gas. The electric heat element had no such problem of course, so the unit worked fine on any electric source. As soon as I cleaned the vent out it worked perfectly. I have now applied insect screening to the inside of my upper and lower vents, so shouldn't have the problem reoccur.
A couple of things I turned up during my research that are relevant to this thread is that, as noted in earlier posts, a lot of effort is directed to obtaining air flow into the bottom and out of the top vent. The whole purpose is to maximize air flow through the condenser coil that is located inside the top vent. Most RV manufacturers install a baffle (the one Phoenix installs is made of thin plywood) to attempt to direct air flow through the coil--and the guidance on this is that if there is no baffle you should fabricate one (sheet metal is suggested) and the more you can constrict air flow directly through the condenser the better. The other issue is the supplemental fan--and again, most RV manufacturers install one (or two). To address Ron's question, the guidance I found is that the fan should be installed midway between the bottom and top vents--not at the bottom and not at the top. (Midway is where Phoenix installed the single fan in my unit). I'm not sure why that placement was considered important, but the most authoritative discussions I found were adamant that the fan(s) should be at the midpoint.
Mike
