[MPerry]

Inside one chamber of the case is a cork flap that gets pushed back and forth moving the wiper arm. In a smaller chamber there is a plastic piece with rubber caps. This diverts the air flow to change direction. Between the 2 halves of the case is a rubber gasket that seals the chambers. Mine easily came free of the cases and was able to be reused. The integrity and thickness of this gasket matters because it seals the cork paddle. There are only a few moving parts inside.

When I disassembled mine there was a fair amount of dirt. Some had hardened to the case and prevented the cork paddle from moving freely.