How can I test to see which one is causing my windows to no longer go up or down?

I am going to the junkyard on sunday and I plan to grabbing some rear ones from a 300E...

Thanks

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k