washer foot switch dilema

[BenzKraft]

I've been assembling a W108-058 (280SE LWB 3.5 manual)  here which the owner picked up as an unfinished project.And because the wiring is very similar to a pagoda, I figured this is the best place to ask.
The wiring has been chopped out  meaning i Have to make a new loom . Because of this ,  I was trying to sort out the wiper motor wiring .The foot switch doesn't resemble anything in any of the wiring diagrams .It has 5 pins. There is a 12Vsupply,marked  15/54 and on each side are the pins which connect the washer pump(1st position)  and by pressing harder, connecting the wiper .
But there are two other pins which are marked  31a and 31b . As far as i know this means they are direct feed to ground. What is supposed to connect to these?

[SEB]

Hi,
You're right — the W108 wiring around the wiper/washer circuit is indeed very close to the Pagoda (W113), but there are a few small differences depending on production year and equipment.

On your 5-pin foot switch:

15/54 – is the 12 V ignition-switched feed.

Washer pump contacts – activate the washer motor when the pedal is pressed lightly.

Wiper contacts – connect when you press harder, sending power to the wiper relay or motor.

31a / 31b – these are not permanent grounds; they are return paths through the switch body, used to complete the circuit for the washer pump and/or wiper relay coil.

Typically:

31a goes to the wiper motor’s park switch or relay (ground control).

31b may be tied to chassis ground to ensure proper switching function or to the washer pump ground (depending on version).

In many restored cars, people simply bridge 31b to chassis ground and connect 31a to the wiper park switch — that reproduces the correct operation.

[BenzKraft]

Thanks Sebastian!,I was thinking that was the case. I had also  been wondering how the park position was obtained .
On my 300SEL 6.3 ,the foot switch also has the 5 pin foot pump switch and the 31a and 31b pins are connected with a Vi Ws Ge lead which could have been a clue but that also is missing from the wiring diagrams.