Hotpoint fridge freezer not getting cold enough?

Hi, i have just bought a second hand Hotpoint under worktop fridge with a small freezer compartment for our caravan, i have put it outside in the garage to try it, it dosn`t seem to get cold enough i have turned the control up to full but the freezer compartment dosn`t ice up all though it is cold i don`t think it would freeze an ice lolly, what could be wrong with it please, thanks in advance if you can answer this question.