Brand new Dometic fridge is worthless

FR, and almost all other RV manufacturers use these for the benefit of those that want/need to boondock. If you're going to be away from shore power, and you need refrigeration, the absorption-mode refer is probably your best choice.

Now there may be additional things that you can do to improve them. I'll probably open ours up to see about thermocouple placement, and ventilation fans, and overall venting. You'd think that FR might have done this already, but then again they are largely just assembling components.

I wish they had a care & maintenance manual. It doesn't exist; you just get a pile of "documentation". No problem, those of us using them have created our own manual.

I just stumbled on this thread and I thought I'd respond to the actual first post with my take on the RM8501 situation.  Possibly this is helpful.  

Three things.... 

First, in my experience the ammonia cooling system seems to be a bit "binary".... depending on the heat input to the boiler, it either cools normally or it does not cool at all.... even with a flame present.  I suspect this is the nature of the design, not a flaw.  In my case, our three year old RM8501 suddenly refused to cool on propane.  The flame was lit and hot gasses were exiting the top of the flue.  But the fins were kinda like you describe.... cool but by no means cold and the refer was warm.  I thought we had killed it until I discovered (when we returned home) that it worked great on AC power.  I cleaned the propane burner / gas jet / flue (which all looked perfect) and BAM.... it cools fine on propane again!  The only thing that changed was (I assume) the size of the flame.  It might be worthwhile to clean your gas jet (I know it is new, but....) and also check the pressure at the burner.  Also make sure no one has made a home in the flue or burner area.  

Second, as has been said elsewhere there are limits to the max outside / inside temperature differential the ammonia system can maintain.  I'm guessing 100 degree outside air temp is pushing it, especially if the refer side of the trailer was facing the sun.  But I am not sure that explains the fact that your inside fins were not cold.  That sounds to me more like an inadequate flame or blocked flue.  

And third, it is possible to permanently damage the cooling unit by running too far off level.  If this has happened, it is irreversible, VERY expensive to fix and not covered under any warranty.  When I thought that was what had happened to ours I called Dometic and they totally blew me off with a carefully rehearsed speech.  I was furious because this "little" tidbit of information is not in ANY documentation we received with the trailer or refer.  

Hope this helps.  

Paul

         Gary