if its a frost free unit the most likely fault is that it is not defrosting due to defrost heater failure, it may also be down to banging the door/s closed causing the other one to open partially causing a rise in temp. and continuous running of compressor trying to compensate but causing an ice blockage in the process, if it has a fan assisted compressor see that it runs and also check for dust build up around condenser
keymatic irl., June 2013