Start by trying this. The orifice that is in your frig is probably
restricted from age. Oxidation that is.  To clean it , the frig will need
to be removed.Even then alcohol will not clean this stuff out. A new
orifice is best($20-$75), but I cleaned mine with muradic acid to get it
right(for now anyway).Then I rinsed with alcohol. The point is that if it
works on 110v OK,but not propane, a restriction probably exists. You can
compensate for this restriction by just turning up the gas. The regulator
on the tank under the vehicle has an adjustment. Turn the screw inside the
black plastic cap clockwise about 1/4 turn and see if the frig gets colder.
Even though the pressure is increased, the actual ammount of gas is not
more that is (11 inches of water colum)supposed to be there.I think the
burner can handle  this additionad pressure . The burner works well on the
bypass flame which is only 3 inches of water.I would turn the screw about
4 ,1/4 turn increments over a couple of days to get the best tempature.This
would corrospond to 13 inches approx. if no restriction existed. Any more
than this probably means that you need more work on the frig.