Abstract: An apparatus for filling a washer fluid reservoir of a rear wiper system includes a fill cup assembly having main body and a cover. The main body defines an opening for receiving washer fluid. A first conduit provides fluid communication between the opening and the washer fluid reservoir for the transfer of washer fluid. A second conduit allows for venting of the washer fluid reservoir back to the opening and provides complete exterior venting of fumes. A vent passage defined in part by the second conduit is blocked when the cover is rotated to a closed position. A designed-in interference normally retains the cover in its opened position.