Your turn signal lever needs to be replaced. Specifically, the microswitch that activates the high beams or turn signals depending on how you aim the lever.

I think the lever and switch is a complete unit though...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car