Barrie's pin diagram while for the 124 works perfectly for the 126's, at least through '86. Likely error is the green wire has faded and you think it is the white. Getting those swapped could give the result you experienced.
The only way the US wipers will work is by adding a bracket to offset the wiper motor. I used a short piece of perforated strap which allowed the proper offset.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.