The Switch you have found is a vacuum/pressure switch, manufactured by WORLD MAGNETICS CORP. The part Number is PSF109.
This is a very common pressure switch and can be used in hundreds of pressure monitoring applications that require a "OFF-ON" set point triggered by pressure via an electric input.
I do not know what it does in your specific RIG, but maybe one of the Alpine owners is familiar with what it controls and will chime in here. My guess is it has to be a part of your Air Conditioning-Heater system.
Here is a Spec Sheet on the switch:
Good luck - Glenn