Samsung RS21 still not working?

Hi
Unfortunately I have a dodgy Samsung American style fridge freezer that developed the common fault that affects this model. As it was outwith the 5 year warranty I've been trying to fix it myself.
I've changed the defrost sensor and the evaporator cover and using a simple thermometer, the bottom of the fridge is around 5 deg C, the top is about 10, all the while the temp Display on the outside is set at 2 Deg C and displays this.
Any advice as to what to do next?
Any help would be appreciated as I live 3 hours from the nearest registered engineer.
Thanks

John A
August 2009