domestic problems- hotpoint mistral fridge/freezer

[Northdude]

i hav a hotpoint mistral fridge freezer, the fridge is not doing anything, i am a fridge engineer but have never looked at domestic kit so not 2 sure about the controls, the compressor, gas and condensor fan are all working ok, the evap fan in the freezer isnt starting up but has no power 2 it and door switch is working ok as i unplugged a sensor and the fan did kick in, is this fan supposed 2 run continuousley like on commercial kit? There are 2 sensors, 1 in the fridge and 1 in the freezer but im guessing they are ok as they are both displaying the right temp, -20 freezer, +17 fridge, so does anybody know how the fridge temp is controlled eg airflow and cooling as i have never looked at domestic before, thanks in advance