The switch behind and to the left of the driver's head?
On mine, it's the switch for the StarCool.
I leave the main rotary switch for the StarCool, which is located in the rear of the van, on "low", then turn the whole system on/off with the switch above the drivers head. It's very convenient when you're driving and want to turn the StarCool system on.
2005 Ford E-350 Diesel Sportsmobile
EB 102 Voyager top, 3.55 rear, Mobil 1 all around
270 amp alternator, billet water pump, coolant filter kit,
aluminum radiator, X-Monitor with pyro, trans temp, boost
+ Scan Gauge & SCT Live Wire (Economy)