Why does a fridge temperature fluctuate?

[HootingOwl]

I have a ten year old Liebherr fridge freezer. It is a standard type - NOT a frost-free model I have a digital thermometer in the fridge cabinet with a minimum and maximum memory. The temperature is fluctuating between 2 degrees and 9 degrees. I have opened the door in the morning to find the actual temp at 9 degrees so it is not a case of room temp air filling the cabinet when the door is opened.

Freezer compartment seems perfectly okay.

Pointers welcome - is it worth repairing?

 

[Burnerman]

The switching zone of a thermostat (or rather the thermistor within) is called the hysteresis - in other words it won't turn off at 6 degrees (for example) then back on at 5 3/4 deg....they are rarely as accurate as that.
A new thermostat is likely to have less hysteresis than an elderly one.
John