Fridge freezing. hi there , have fridge freezer approx 12- 14 years old, fridge is freezing just

Question

hi there , have fridge freezer approx 12- 14 years old, fridge is freezing just like the freezer does , have already replaced the thermostate. twice just in case, compressor is running all the time, could it be low on gas...... this is afisher and pykel c240b fridge freezer....thanks ,