The 410 windscreen washers are actuated by a simple push switch which is mounted on the back of the fiendishly complicated wiper switch (which by the way has to achieve a polarity reversal to the wiper motor so that it reverses to the park condition)
My memory tells me that this push switch applies an earth to the black and green wire that you mention coming from the washer pump, so if I'm correct there should be a black wire (to earth) and a black and green wire (to the washer pump) coming from this push switch. There are inumerable wires coming out of the wiper motor switch itself
The normal colour coding convention on vehicle wiring is that green wires are normally live when the ignition is on. So it appears to me that there is a live supply to the washer pump all the time the ignition is on. The colour coding of the black and green wire implies that it is earthed, via the push switch, when the washers are required, which completes the circuit.
Your description of the 411 wiring diagram, that the green wire to the washer pump comes from the washer switch, and there's a black wire from the pump to earth suggests that the 411 arrangement is entirely the other way round, i.e.
its the feed that's switched on the 411, not the earth.
It is relatively simple to get to this push switch if you need to. First remove the padded strip that runs across below the dashboard. Most of the screws are fairly obvious but my memory tells me that there are two that are not so obvious at each end of the strip towards the front of the car. A slight complication is that the fresh air inlet control is mounted on this strip, so you have to take that off the strip as well if you need to remove the strip completely, but you may be able to work round it.
It's also, from memory, relatively easy to take the whole wiper/washer switch out, if you need to. The knob is, I seem to remember, held on to the shaft by a spring loaded plunger, which you press in with a nail or whatever from underneath and the nut that holds the switch on will then be obvious to you. But don't do this before you take aforementioned padded strip out as you need to take careful note of what wire goes where on the switch as soon as you possibly can as the 407/8 wiring diagram is no help whatever if in this regard.
If you need to get your head under the dashboard I would counsel removing the drivers seat AND both its runners, which are otherwise inclined to attack you.
I hope this is a help
Roger Morrall
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