I am replacing the seat basket on the drivers seat in my dads 86' 560 SEL, but I am having a terribly hard time because of a short somewhere in the system. I can adjust the seat backwards and I can adjust the back rest without issues, but If I try to move the seat forwards past a certain point the fuse blows every single time. I need to move the seat forward in order to access one of the screws to remove the basket frame, so it's particularly frustrating.

I want to identify and fix the short, but I am not sure how to approach it. Visually I cannot see any wires that are frayed or busted (nothing cut from the bad seat basket either). How can I test continuity on the various lines running to the seat motor?

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1983 300SD White with Grey interior