A DC motor will surely give a kick-back voltage spike when turned off, due to inductance of the armature and the generator effect. But, many are switched off with a manual switch and no protective diode. Protection is more needed with semiconductor switches. I have to periodically open and clean my window switches on the console. I assumed that was due to spilled drinks by my offspring, who don't fess up. My switches still have shiny silver once cleaned. Silver can tarnish (oxidize), so not unexpected. If you take apart the mirror switch in the console, mark the body carefully and take photos as soon as you open it, as there are many ways to reassemble it wrong (how would I know?).

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans