Can anyone suggest what may be the problem with my F/F? The fridge has stopped cooling down but the freezer works.

Turning the stat up sometimes starts the fan at the rear of the fridge, This would indicate that the stat & the fridge fan work ok. Does the fan blow cold air into the fridge or is this the defrost cycle?

Is there a valve between the freezer & fridge section of the refrigerant tubes controlled by the stats? Some ice does form at the rear of the base of the fridge.

I have read about thermistors causing the problem, if it is that, where are they located & does anyone have the part numbers & a supplier I could use.

Any advice would be greatly appreciated.