These RV refrigerators are odd beasts. There's general agreement that they take a long time to cool down. 6-8 hours is often mentioned. Observations and gleanings:
The freezer compartment cools down first.
Load the thing with pre-cooled food, and (one Phoenician suggested) put frozen bottled water in it when starting up.
Seems like the frig needs to be started up the day before departure.
Use a small fan to keep air moving in the frig compartment, and load food so as to permit air circulation. Fans for this purpose can either be wired in, or battery-driven. One model says it runs for 30 hours on a load of D cells. Seems better to me than drilling holes through the case for 12VDC wires.
There's no temperature setting in my model: the manuals repeatedly advise that this is "factory pre-set." But there's apparently a thermistor attached to one of the cooling fins in the frig section, and by sliding this up and down one can adjust temperatures. Sort of.
Constantly opening the door(s) to check on the temperature is counter-productive (!)
The DC power has to be on for control circuitry in the thing to work. (This may have been one of my problems. There's a battery disconnect switch which I have been religiously turned off when I leave.)
Make sure birds have not built a nest in the vent.
While chewing on these issues, I wondered about how much LP gas the thing consumes. That's the only way I can cool it down while in the storage lot. There's a LED indicator in the rig which reports how much fresh water I have on board, how much LP gas is in the tank, how full the waste water tanks are. The LP indicator hasn't budged since I've owned it. Poking around and reading schematics, I learned that there's an actual analog gauge down in the compartment where the LP gas tank is. Comforting. I have more than half a tank. And the refrig consumes least LP gas BY FAR of all the appliances: The shop drawings report:
Refer 1500 BTU
Furnace 31000 BTU
Range 25500 BTU
Water Heater 8500 BTU
It's not clear what these numbers actually mean. BTU per hour? Under what conditions? Max BTU? But whatever they mean, since the refer seems to run all the time, either on gas or 120VAC, I'm glad it's relatively parsimonious.
Come to think of it, I have no idea how many BTU's a full tank of LP gas provides. But wait! This is the internet...
Here's a set of numbers from http://www.exothink.com/Pages/btu.html :
1 pound of propane 21,600 BTUs
1 gallon of propane 91,000 BTUs
1 cu ft of propane 2,750 BTUs
So if I have a 20-pound tank, which one owner of a similar rig said he has (again, no specs anywhere) I have a capacity of 432K BTUs, which might run the refer for 12 days, IF the numbers on the shop drawings are BTU's/hour.
But that 20-pounds seems a bit low, given that your basic "20 pound" BBQ grill tank holds about 16 pounds of propane, and this tank looks bigger than that.
And if I'm not running the furnace.
Or taking a lot of showers.