Check the drain hole at the back of the fridge. It connects to a pipe that runs down the back of the fridge to the top of a plate on the motor. If the hole or the pipe becomes blocked the water can not run away and will freeze. Clean the drain hole and the pipe with a pipe cleaner or (a plastic cable tie ) as it is flexible. Or flush it out with warm water and fairy liquid using a syringe, put a bowl under the open end before doing this. SWITCH IT OFF BEFORE DOING THE ABOVE. Good luck
Paul
July 2012