I've got a new 1969 Kombi wash/wipe switch 141955517 to install. A quick question. The two barbed hose connections are marked "B" and "D".
Which one is inflow, which one is outflow?
Thanks.

Hmmm, good question. I don't know the answer, but I'm not sure it matters either. I guess if the valve can't cope with pressure from the wrong side, then you'll notice leakage when you pressurise the washer bottle. In that case, try swapping them over.

Sorry I can't give you a definitive answer.

I'm fairly certain the reservoir is connected to "B"

I don't know what your part is like, but for a typical washer motor the central hose comes from the reservoir and the side hose goes to the squirty nozzles.

Hook it up and try it - you'll soon find out if it's the right way round.

I'm guessing here, so don't take it as gospel, but you might try:

Behaelter (reservoir, in German)

and

Durchlass (outlet or similar in German).

As has been pointed out, this is only important if the valve is only pressure-capable on one side.
HTH.