Servicing the RV fridge
The absorption style RV refridgerator is a low maintenance device, but there are some things that you can do to help it do it's job. The most important thing is to keep it clean and prevent any obstructions in the venting system.
When operating in the LPG gas mode, the products of combustion are removed by the flue. After a period of time, soot and rust particles accumulate on the inside surface of the flue. Road vibrations will loosen these deposits and they crumble and fall to the burner below. The finer particles fall into the burner itself, while the larger pieces remain on top of the burner and cause problems with the flame sensor. As the fine particles build up inside the burner, they alter the burners volume and shape. This results in an improper flame and affects the heat output of the burner. The flame may look normal, but it is not producing the required amount of heat to operate the cooling unit.
It is hard to tell by looking at the flame - a proper flame and a slightly reduced flame will look the same. There is no adjustment that you can make. The orifice should be soaked in alcohol (no, NOT Vodka!) and allowed to air dry. Replace the orifice if you suspect it is partially blocked after cleaning it. Blow out the burner with compressed air. Check the gas pressure at the refrigerator gas pressure test port using a manometer. You can build your own manometer for a few dollars (see manometer)
for details and instructions. If the gas pressure is not 11" w.c., you may have a thermostat problem or a main regulator problem.
The BTU input (meaning the amount of heat) is about the same for the propane flame or the AC heating element by design. This is because the cooling unit is fabricated to process a certain amount of heat to make the 'cool'. It does not matter to the cooling unit whether this heat comes from a flame or an electric heating element.The heat source, meaning the propane flame or the electrical heating element, is used to "elevate" the ammonia/water mixture to the top of the cooling unit. There after it is gravity and the PHYSICAL change of state of the chemicals that does the rest of the cooling work.
The air flow across the back of the refrigerator is also gravity controlled - hot air rises and flows out the roof vent. Cooler air is drawn in through the bottom or side vent to replace this rising air.
Any assistance, especially in HOT weather, will help with this heat dissipation. A fan to move the air need not be a large one to effect a higher efficiency. Also, the addition of sheet metal baffles to direct the moving air through the evaporator fins can be very effective.
Use a mirror to look up into the back of the refrigerator compartment.
There should be a maximum of one inch clearance between the evaporator coils and the facing wall. If the clearance is more than this then your refrigerator will benefit by the addition of baffles. It may be necessary to remove the refrigerator to install the baffles, but that is not a hard task to do and may result in a very much improved cooling efficiency.
This rising air collects heat from the evaporator fins as it passes by, thus removing heat from the cooling unit.
If your unit cools better/faster on one source as compared to the other, there is most likely a deficiency with the other system.
Trouble shooting the cooling unit
More on the RV refrigerator
On-line resource - Cooling Unit