To clean those dirty contacts on markers, stop and taillights, the turn signals and trailer connector/receptacles, I use approximately 1 ounce of cider vinegar and add a little table salt.
I apply the cleaner with an acid brush or similar applicator, and when the contacts are clean, rinse them with water from a spray bottle. Then I dry the contacts with a hair dryer (you can also use compressed air).
Works great here in rainy country.
— Chas H. Webb | Gresham, Ore.
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