The is an error in my diagrams, I will be fixing it soon!
The Blue wire is (Terminal 5 Low speed) and is opposite the black wire (Terminal 2 Ground wire) and Blue/yellow wire (Terminal 6 High Speed)
Troubleshooting the Combination Switch Wiper Side and Harness Plug
The Datsun 240z had a different combination switch for each year. The switch changes the continuity to ground for the circuit. Troubleshoot the wire harness plug first, then the combination switch. The blue/red wire is power from the fuse box. The contacts in the switch may be have carbon build up and need a good cleaning.