The purple wire is usually circuit 50 (starter activation at solenoid). The two big connections carry all the current for the whole car short of the starter. But you have to understand that statement.

The battery powers the starter with the cable the size of your finger. It takes that size cable to handle the current of starting. Everything else comes from there and is powered through those two leads. Your radio, your A/C, your ability to make a starter start, go through those two screw connections. Before those connections the big braided wire comes from the starter solenoid upper connection grouped with that wire the size of your finger.

You have corrosion like we never see in Florida (except from northern cars). You have the ability to have some real story telling problems with those connections. That buss bar is available from MB probably fairly reasonable. I would order one with screws (they will have to be ordered individually). Replace it and clean the wire connections with a wire brush. Some dielectric grease would do a good job corrosion protecting the final result. I don't remember what car we are talking about or I would post the part number.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician