If I understand you correctly, you added a fan in the food part of fridge and not the freezer?
The working medium passes through the freezer first, so adding a fan seems to me to do nada for the freezer. I know it makes no difference in my freezer whether the fan is "on" or "off".
Adding a fan to the "back" (chimney) of the fridge does improve cooling time and freezer operation.
philh wrote: I added a computer fan inside the fridge. Freezer easily keeps ice cream frozen.