rear defrost wiring 71 fastback mach 1

[heavyhopper]

at the switch i have constant, ignition, and a black /white wire that sends 12 volts while you hold the switch, which leads me to believe the switch is bad? also the connectors on the rear window are there but no wires running to them, does the the black/white wire go to the window? or does one side of the window get grounded? this car was totally apart so we r trying to get this basket case back together which is pissing me off! thanks