What does this switch activate? 87 300TE euro

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92 300D. 163K. Brown on Beige
87 300TDT. 213K. Black on Saddle.
85 190D. 183K. Red on Saddle
83 280SL. 165K. Champagne metallic
87 300TE. 240K KM. Parts for the 300TDT
87 300D. Thanks DieselPaul
84 190E.