My Whirlpool cb18m Fridge Freezer works fine but

check to see if the evaporator fan is working in the back of the freezer panel

Hi...

Try to follow the intruction that i can give

Check the temperature setting
Assure that there is enough room for air flow in the refrigerator or freezer
Check for air flow restrictions in vents
Test the temperature control
Clean the condensor coils
Check the door seals
Test the door switch
Test defrost heater
Test defrost timer
Test evaporator fan 
Check for a clogged drain tube 
Check for refrigerant leak

Good luck !!!

Regards

PCmania