Take the fridge out and turn it upside down and then put it in a car or other vehicle and drive around for an hour or so.
This shakes up the compressant liquid which tends to to set after some years service.
Take it out and refit the fridge but allow to stand for 24 hours before switching on.
I did this to mine and it worked perfectly afterwards.
This is also useful if the fridge works but is not very cold.
paul battleskips
July 2009