I am trying to determine which wire going to the back of the instrument cluster activates the right turn signal indicator. Car is 87 300E. Outside turn signals all work fine, both sides. Right turn indicator does not come on or blink though. Left one is fine. Bulbs are all fine. Thanks for any info.

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2005 Mercedes C230k sport sedan, 6 speed
1987 Porsche 924S - 968-engined track car