That switch is most definitely the refer fan switch. As SilverRanger noted, it's wired to a thermostatic switch, so unless the refer is fired up the switch will have no effect.
To check it for yourself, fire up your refer for an hour or so. Once the plumbing is warmed up enough, you'll get an indicator light in that switch when operated, and you'll hear the roar of the factory cooling fan...then you'll want to do a search for "refrig fan noise" on these forums to find out the ways you can quiet that beast down. Seriously.