Fridge not cooling

If you go to around slides 17-20 you can see that the COP of an absorption fridge is related to three temps (To-condenser/absorber), Te -evaporator, and Tg -generator). I didn't run the numbers, but since To (essentially the ambient temp) is showing up twice, in the denominator in one case and subtracted in the numerator in another) COP is going to fall off quickly with higher ambient temps. And if COP drops cooling capacity drops along with it. To run the numbers you would need Tg, essentially the hot air from the propane flame or electric element. I found one reference for that which is around 350F. Note that you would need to do this calc in degrees above absolute zero (Rankine or Kelvin degrees), not in F or C. 

The reference with the Tg of 350 was this, which is an interesting discussion of what causes damage to RV fridges and how to prevent it. 

Here we sit with fridge running on propane for 19 hours.  Setting is on 4 of 5 dots, 5 being the coldest.  Temp has stabilized at 41 degrees, not near as cold as when I was on electric where it went down to 36.  However the fridge side is sitting in the sun and current ambient temp outside is 92 and I also checked inside the freezer and it was able to make ice overnight during the past 14 hours.  So what temps do you all have when running propane?  Is 41 acceptable or do you think this is on its way out because it is nearly a 10 year old unit?  The only thing I have left to do is to take off the supply line  from the regulator to the fridge and see if there is any oil or residue to blow out.