Unscrewing the bulb will not disable the switch, so opening the door on Shabbos while the fridge is running will turn off the fan, and on when closed. Since it is extremely silent, pick a time when it is quiet like at night. Open the freezer and bottom door at the same time while the fridge is running. While listening in the freezer, press in the switch located along the inside bottom-door wall. If the fan starts, then you have a problem, and the switch needs to be taped down.
Some models also have a switch in the freezer.
I have seen this problem in European and Japanese models and now in a Westinghouse that someone has, so it may be fairly universal. They will be glad to send you material detailing their arguments on grounds of both halacha and morality. Whey is the watery part left after milk has been coagulated and the curds filtered off. It's clearly a dairy product. It's kashrut status beyond that gets pretty complicated since it depends on how the milk was coagulated, whether the use of animal rennet renders the whey traif either because of mixing milk and meat or because the rennet itself is not from a kosher animal, and last but not least, the kashrut of the original milk.