Screen wiper robot K2599 fitting to early bay window VW

Hi
As the title says I am trying to fit a K2599 early bay window VW (1970 model), the diagrams in the booklet are clear but have tried to follow it through with the vehicle wiring diagram and it is not showing the same code connections as the velleman diagram, on the vehicle wiper switch I have 30,31,31b,53,53a,53b.

30 to fuse box, terminal 15
31 to ground
31b to ground
53 slow speed
53a park position
53b high speed

I don’t have a number 15 or 53e as shown on the velleman diagram.

I believe this early bay model of VW transporter has a different wiring to the later models (something to do with the earth I believe).

I have tried to work it out and have connected it up to what I thought was correct but although the unit seemed to be working the wipers just carried on running as normal.

Anybody know what the correct connections are for the K2599 to my switch.

Many Thanks for any help.

Sorry, we do not have wiring diagrams for this particular vehicle and model.
Hopefully somebody in the community can help you out.