[wingnut60]

Glenn,
Your fridge should be similar to mine--Dometic RM1292 or close--and it generally is a good working unit. First item to consider is the thermistor located on the interior fridge coils--should be located on one of the fins-- that can be moved upward/downward. This is the first method of adjusting the inside temps. Can't remember which direction moves the temps up or down...you can also disconnect this thermistor and the fridge should default to coldest setting possible where just about everything in the freezer and fridge would freeze. If you do this, and it gets really cold, the fridge is working ok. Be aware, you probably will never get hard ice cream with this unit...
If fridge shows to be able to get real cold, then the next area to check is the venting of heat away from the coils--this is a drawback to slide-located fridges, the top-vented ones are much better at natural air movement due to convection currents. When the air has to make a right-angle turn to get out the upper vent, it slows down the movement and gets warmer in that area. Also, in the upper vent area there should be an auto-operating thermostat switch located at the upper left top of the coils ( a small gadget with 2 wires--one in, one out) that controls a vent fan that is most likely located down lower where it almost can't be seen because you can't get your head into the opening to look down. That fan (should be there, if not that is a lot of the problem) may be dead or the auto switch dead or both. I took the auto switch out of the circuit and am using a simple on/off switch located in the lower vent area, then used the same wiring to control 2 12-volt computer fans that I placed horizontally in the upper vent area that suck air from the inside area and exhaust thru the upper vent.
Between all this, my fridge has worked very well over the years--the fans I turn off when not on shore power unless parked in sunlight or warm areas.
Hope all of this helps you somewhat.
These fivers are life-long projects that will frustrate you at times, then provide lots of fun when you get it right.
If you like the trailer, and won't be doing much off-grid camping, a replacement with a residential fridge will fix your concerns.
Joe