How very odd. I just went through the w115 FSM and that switch doesn't show up in any of the images/diagrams. The reverse light switch is mentioned and an adjustment spec is provided, but I was unable to find anything helpful regarding your question. So basically, I need not have even posted. haha.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).