I've used the 2 D cell type fans for years mostly to help get the frig cooled down a few hours before leaving home. They didn't seem to do much after the frig was cold.
But last winter in Florida for 4 months, we ran into a problem within 2-3 weeks. The frig just wouldn't get cold enough, and it wasn't that hot outside.
If I put it on 5 the highest setting, the fins just got heavy frost on them. The lowest we could get it inside was 39 degrees. That was using a thermometer in a glass of water.
Finally I got a 4" computer fan and mounted it about 10" in front of the fins. It's running on 12 volts from the frig's control panel.
I really couldn't believe the difference it made. Now it stays down around 35 degrees and that's with the temp control set midway on 3.
The other thing I couldn't believe is now no frost ever forms on the fins, even after running over 3 months straight.