I think its time to give in and buy a new wiring harness

cudamark said
There's a few things that work pretty good. I like to use a glass bead blaster the best. If you don't have one, you can soak the connectors in some cheap white vinegar for a few hours, then rub/brush them in baking soda to remove corrosion and neutralize the vinegar. Same goes for lemon juice, they're both slightly acidic and will remove most corrosion and not hurt the plastic plugs. After soaking, neutralizing, and drying, spray some lithium grease on the connectors to help keep it from corroding again. I also like to squeeze some of the connectors a bit tighter before plugging them in again.

Personally, I think this is some of the worst advice you can give. If you get it on the conductor portion of the wire, you will NEVER get that vinegar or lemon juice or whatever neutralized where it's wicked up inside those wires. Never.

And even if you did, any moisture, whether acidic, basic, or neutral, is never good inside a plastic-insulated wire, whether multistrand or single strand. Once it's in there, it ain't coming out. It might take 1 year or ten, but it will end up corroded internally, and that's the worst kind.