Common problem which has been covered in a number of threads but can be a pain to find, firstly read the installation manual for the fridge, if none in van you can get it online just google model number, once you have read it remove the outside vents and look inside to see if the thing is fitted properly, namely the the top of the fridge should be enclosed, you should only see the back of the fridge, a baffle plate should be fitted so the hot air is directed out the top vent and the sides should be sealed, no gaps along with any cable runs, many you can find allow the hot air to swirl around in empty spaces even escape thru unsealed cable runs into cupboards, this also lets in dust, the air should come in at the bottom pass over the cooling fins and out the top, it will be quite warm behind there around 60-70 deg so don't be alarmed, thats normal, fitment of a fan is easy most times and greatly enhances the operation of the fridge, fitting a shade over the side wall also helps ....... it is also wise to run fridge on 240 for a day before use to get the whole cabinet cooled down, try to keep the thing nearly full also helps BUT don't use it for drinks and keep kids away or it will never stay cold... I keep my beer in an Engel.
I'll see if I can find a write up on doing the fridge fan...........some go to great lengths but I just sikaflex them to the vent now and fit a switch..............
Bit on mods for my old 14.44 .....
https://www.expandasdownunder.com/threads/drovers-14-44-3.4502/