AEG Santo 72398-6KA Fridge?

My 6yr old fridge has stopped cooling. The lights are all working, the internal fan is running, the compressor is humming - not vibrating, and is very warm to the touch - any suggestions? I've had a look elsewhere and have found suggestions of a hard start kit, or possibly the thermostat, but would selcome some knowledgable advice.
Barney, January 2016


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