Help understanding please

hyedenny said:

Take a look at the schematic, it IS a single wire

Click to expand...

What I meant was that it isn't possible with a single wire where there is only an on-off function on that wire.

That is why I think there is a more complicated signalling system.

Here's a wiring diagram from shopkey , theres no body computer in this circuit unless that's what your calling the relay panel?? Hopefully this will help sense your other diagram isn't very good.

Fuse F52 is irrelevant in this drawing, and M56 relay contacts can be jumped to test the wiper motor.