After trying the previous suggestions try the following:
I have a 2008 Fleetwood Discovery 40X with the refrigerator in one of the slideouts. The rig spent weeks at a service center, refig. was tested okay with no food inside, but would not cool below 40 degrees, which Dometic insisted was OK (not according to U.S. government food safety guidelines). It turns out unit was not installed correctly. We insulated both the top and sides, installed a baffle (insulation) to direct the heat out the side vent, installed two computer fans under the coils at the bottom of frig. and it now works fine 33 and 1 degree in freezer. Don't need fans on unless trying to cool fast or it is very hot.
Not sure what your rig is, but if it is in a slide out try the above, if not try a roof vent fan.