This is a common problem with this model due to it being a non frost version
Simply moisture inside the fridge/freezer needs to escape by way of a drain-hole at the back/bottom of the fridge (inside the freezer compartment), this water is then directed to the top of the condenser to evaporate. After time this 'hole' gets blocked, the water remains inside the freezer compartment, builds up and blocks the flow of air to the fridge
The big give-away for this is the bottom freezer draw is jammed (by the ice)
This easy to resolve, an engineer would only do the same (I did this recently) approx 4 hours and working again
Power off fridge/freezer from mains, remove content from freezer (as this is where all the works is done)
Remove freezer draws, bottom draw will/may be jammed
Use a hairdryer or whatever to free up the bottom drawer and ice build up
Using a Philips screwdriver, remove the back panel, whilst unplugging the connector block behind panel, do not force off due to ice holding as it will snap, ease off with hair-drier and gentle tugging
You will now see a sheet load of ice, that's why the fridge isn't cooling
Simple defrost ice with hair-drier
With a thin piece of wire or whatever, unplug the drain hole in an attempt to stop this again, albeit I've had to repeat the above 3 times now in 3 years
Good luck
Below is picture with back panel removed
http://stevemorgan.co.uk/linkfiles/fridge.jpg
Steve Morgan, May 2012
