yes the freezer fan should only run after defrost.Dependent on age some will start straight after defrost some will require the evaporator to be at -15 approx.
Does the defrost stat control the fan, i had a short circuit defrost heater, disconnected the heater to stop tripping but the fan would run for a few seconds and then it stopped, so if the freezer evaporator doesnt get to minus 15 then the fan will not run? Thanks ace