white housing...
doesn't fit flush with the fan case. Do you have the exterior motor housing? This covers everything and attaches to machine with 3 Phillips screws.
As for the black wire, it is probably disconnected from the switch. Maybe someone will have a diagram to show exactly where the black wire fits.
The switch itself has to be manipulated gently into position when you are putting on the exterior motor housing so that the plug and push button fit in their respective openings. The switch is then tied down with two screws, one in the top of the housing, and one underneath. Double check that the plastic around the switch isn't broken and that there is a clip on top so that the top screw can secure it.