Whirlpool Fridge Freezer

Mod ARZ 864/H This fridge freezer is not frost free but has no cooling in fridge although freezer is fine.It also short cycles. It has one of those solenoid diverter things on it that diverts the gas into either fridge or freezer. What is it that can cause this problem in that it is not allowing gas into the fridge? Is it the sensor in the fridge or the board? Ive had the same problem on some of the Hotpoint ff fridges with the soenoid on them but dont know what cures the fault. Changing the solenoid if faulty does not seem an option as it entails re-brasing capillary tubes x2 and re-gassing. Is anyone aware of this problem and how to fix it?

Thanks

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