1 Check if that fan is running in the freezer. you may have to press the light switch in to make it go. 2 then check if there is any ice on the back wall in the freezer compartment about 30-40 cm from the bottom, if so then fridge is not completing it's defrost cycle and the evaporator ( cooling element )will be blocked by ice stopping air flow.
Fridge Guy, June 2010