I am working on a 1972 240z (build date 11/71) with my son and we have hit a small snag with the combination switch.  Everything about the switch is working well except the washer motor wiring.  I press the button and nothing happens.  I know the pump works as it is new and I have tested it with a 12v battery.  I have also tested the all wires on the switch, both on the connector and an additional blue/white wire that resides outside the connector and is currently unconnected.   All the connections seem to work as they should except this blue/white wire which has no obvious home/connection and it goes to 12v when the washer button is pressed (see pics with wire circled).  I have no clue where it should be connected as there is no obvious connection point.  Can anyone give me a clue?

BTW, the switch is unmolested, was fully reconditioned and works well.  The car came to us largely as an unassembled project and we have made excellent progress to this point.  I am sure I am missing some connection point for this wire but it is not obvious where to connect it.  Any help is appreciated.  Thanks.

One additional point, I did do the honda wiper motor swap with relay so that might be causing part of the issue.  However, the fact that the blue line goes to 12V when the button is pushed is still an enigma.  I believe the wire should connect somewhere but it is not clear on my harness.  I have replaced both the dash (used in great condition) and engine (new) harnesses along with the fuse panel to blade type so it could be a mismatch of parts that is creating the issue.

The blue/white wire is connected to the wire that goes out to the washer pump. In the wiring diagram, that wire is labelled as black/yellow. However, I do not have first hand knowledge if that is correct.

You should look for a female bullet connector in the dash harness at the steering column that is not solid black. The wire should be the same gauge as the blue/white wire.

Thx, I found the wire. The black with yellow stripe comes in on the turn signal side of the switch (see picture, blue arrow pointing to the wire). I had the ground connected there. That ground, which is on the turn signal side, connects to the ground on the combination side of the switch (see picture, red arrow pointing to the wires). After that all was good. I wondered why the circuit seemed to work fine with my crossed wiring of the black to black/yellow. As it turns out the switch was finding ground through the wiper motor. As I was tracing the wires for the second time, I disconnected the wires at the wiper motor and found my headlight would go out... Eureka! Problem is now solved. Thanks again !