I have an old fridge freezer in the garage which the freezer is ice cold as it should be but the fridge is warm , there is no fan on this as it is too old , I have defrosted it and checked the drain tube but it is still the same , any thing else I can check , obviously the unit at the back works and the thermostat is switching it on and off , how is the cold passed from the freezer to the fridge ????? It's only my beer fridge so it's not worth spending anything on as it's certainly over 15 yrs old . Thanks in advance