Has the OP answered the question that the fridge does or does not work correctly on AC?

If it does work fine on AC power...is there a different cooling method for that (other than the 12V DC level possibly being too low without the inverter running?)...just curious as to what makes cooling on AC different over LP?

The differences I can think of is AC has no flame (so the LP delivery system could be suspect as indicated above) meaning the AC uses a different method to 'heat' the ammonia in the closed system.

AC uses DC power for the control board thru an inverter and not directly relying on the battery level?

Others?

What else could make it operate on AC but NOT on LP if that is the case here which I don't ever think the OP provided that information as to whether it worked on AC...???

Just some thoughts...

Joe.

 

A/C power has a heating element, D/C also has a heating element. L/P uses a flame, a little bigger then a pilot light. Ussually L/P will result in the best cooling. Unless of course the orifice is plugged, and those darn spiders, just luuuuuv the smell of propane.

 

Dometic (and competitors) actually make three "types" of absorbent refrigerators - as far as I know all use ammonia and a few other nasty chemicals to complete the cooling cycle.

The most basic is a gas only - the gas is "on" all of the time, the cooling shutoff is controlled by a mechanical thermostat. Some models also have a 120 volt heating element in the "heating" area. The change over from gas to 120 volt operation is handled with a huge mechanical switch that separates the gas and electric functions.

Next up is a combination gas/110 volt - but the switchover operations are controlled by a 12 volt (RV battery) electronic circuit board. These units are probably the most common in RV's. The switchover from gas to 110 volts is usually seamless, with the 120 volt system having prevalence over the propane. If the system is operating on 120 volts, then loses the 120 volts, the 12 volt system (the RV battery) will automatically light the gas system to the boiler. Operating the Dometic while traveling on the road has been debated on many other Forums - some say it is OK, others cite the increased fire possibility caused by an open flame and the (possible) wind whipping caused by travel. Everyone need to analyze their own levels of acceptable risk and need.


The third type of refrigeration system combines three types of heating elements, one with a gas system as described above, another with a 120 volt heater, also as described above, and the third element comprised of a 12 volt heating element.

This third type (12 volt) is usually found on self contained Class A and Diesel pushers. The 12 volt heating element only works when the circuit boards sense a 12 volt system input of over about 13.2 volts. This is usually sensed when the alternator of the engine is in operation (when traveling down the road). This "3-way" system is undoubtedly the safest, but it is also the most complex, and most users find the circuit boards need to be replaced every once in a while. The 12 volt heater draws around 25 amps, so it will drain a storage battery fairly quick, which is the reason the "smart" electronics only allow the 12 volt heater to operate when the engine is running. These are usually not used in trailers or 5th wheelers due to the huge (4 gauge or larger) cable required between the Tow Vehicle and the trailer to maintain 13.2+ volts between the battery and the refrigerator with such a huge amperage draw. If the refrigerator brain sensed a voltage less than about 13.2 volts, it will default to the 120 volt heater, if 120 is not available, it will light the gas heater. Of course, a 12 volt (RV battery) source is required to do the electronic switchover and to supply voltage to some sort of a spark to light the gas system.

Hope this helps - Dometic "schools" are available from multiple sources in the internet, and usually manuals from most any model are available free for the downloading.

I have had three Dometics (one of each of the three types above) and have found the best cooling to be on 120 volts. The first thing I do if the cooling is questionable is to add a small fan to the backside of the fridge to assist in cooling air coming in the bottom, moving over the coils, and then exiting out the fridge vent. In some instances it will be very difficult to accomplish cooling any closer to a 30 degree approach.

 

87mh...
Nice rundown on Dometic fridges. My side x side unit has 2 fans for the cooling coils--these are a necessity on the ones that have the fridge in the slideout and upper vent is on the sidewall, not the top.
Thanks,
Joe