Butter warmer.

[wildwood]

How does the butter warmer in my Fridge door work?

There is no wire from the actual fridge(s) to the door so why is there a 3-way switch, it is obviously is not electrical.

[Mosaic]

No idea, but it sounds handy for incubating eggs. You could have your own chicken run.

[Dodger666]

I thought that "butter warmers" in fridges were simply compartments at the top of the door which will be the "warmest" part of the fridge interior.

What model fridge is it, and where is the 3 way switch?

[beso]

It is a poorly insulated part of the door. The switch changes the flow of air and hence the effective cooling of the compartment.

[AlBags]

All the cheapest and worst insulated fridges have great butter warmers : )