aus USA habe ich folgende Info:
the 2 Brake Switches were combined into one unit. (Which was covered by a BMW Recall BTW.)
The switches are
S29 Brake Light Switch shown on pg 6325-00 at
http://www.e38.org/e32/e32_88_etm.pdf
and S30 Brake Light Test Switch shown on pg 6200-13.
S29 uses pins 1 (VIO/YEL) and 2 (BLU/RED) of 4-pin connector X78 which is shown on pg 8500-04.
S30 uses pins 3 (BRN/GRY) and 4 (BRN/BLK) of X78.