Just got done fixing my rear window problem.
Checked the fuse=OK
Checked the Switch, Took it apart, tested it and it all checked out OK
Back to the "black box" in the rear, Looked at the circuit board and realized I had no idea what I was looking for.
Then I noticed the corrosion around the wires going into the box, A couple had rusted, broken off.
Tried to find the metal connector that goes inside the plastic housing, No luck.

The way I fixed it was to attach a larger gauge wire that would barely fit into the plastic housing, What this did was fill the space where the male portion would connect with the female which was replaced by the the large gauge wire.

Next I taped the heck out of the connector to keep moisture out of the connector.