On the '71 cars, one of the stock pusher fans was controlled by a manual switch. The second stock pusher fan was controlled by a thermo switch.
The manual fan switch was quickly discontinued if favor of a second thermo switch in the radiator. This left a "dead" switch in the panel.
The manual fan switch was wired "hot", meaning that the fan could be turned on at any time without having the ignition key turned on.
John