zanussi fridge/freezer icing up in fridge compartment

my zanussi model zfk61/27ral is forming a large ice chunk on the inner rear wall of the fridge. i am told it is the compressor unit. could anyone help me by confirming this and if this is the fault tell me is it an easy job to carry out the repair thanks to all jimcas

unplug and defrost for 24hrs and make sure the drain hole is clear
you need to leave it for 24hrs as the internal air channel can fill with ice unseen

tried turning it off for 24 hours but after turning back on it was o.k for about 10 hours then started freezing up again on the thermostat housing and on inner rear wall of fridge to the left of the housing.would that make it a problem with the thermostat or is what i am calling the thermostat maybe the demister housing and i have the two mixed up many thanks Jim

Check cooling fins or coils are free of dust to ensure that heat is lost from he appliance. My integrated fridge used to freeze up all the time and never went into defrost mode despite loads of ice on rear wall of fridge. Vaccuumed the coils clean of a small amount of fluff/dust and has worked great ever since. Assuming that there is adequate ventilation to appliance and that it has not recently been boxed in or the like.preventing het loss.