Bongo Fury

Hi - Every year we seem to get a new problem with our Waeco CF-25 fridge. This time the digital display reports the temperature as 52C, rising to 57C or higher when its left running. Inside the fridge, its arctic conditions, beer and milk frozen solid. So, the fridge always thinks its above the set temperature of 03C and just keeps cooling to negative temperatures, running down the battery in no time. Presumably its the thermostat? Does anyone know if its easy to fix? I'm a bit loathe to chuck it, despite the poor reliability.
Thanks.