2 connections behind driver side floor heat exit

[Uoroxxor]

there are 2 white connections behind the driver side floor heat exit. One is used the other is unhooked and missing. the one that is used is pluged in by the huge black cable instantly but the other is blank. Anyone know what that is? the ac/heat/windshield wipers/rear defrost and speedometer lights aren't working.

Any ideas? Thanks