Liquid damage to a switch or connector

Liquid spilled into a switch or connector — a drink into a console, water through a failed seal, or washer fluid into an engine bay plug. It is worth separating from ordinary corrosion because it acts differently: the damage begins immediately and continues invisibly for weeks after everything has dried.

Sugary drinks are the worst case. The sugar leaves a hygroscopic residue that draws moisture back in and conducts, so a switch works intermittently, then reports two positions at once, then fails — and the connector looks dry throughout. Corrosion travels along the conductor inside the insulation, so the damage reaches a connector some distance from the spill.

The timing is what identifies it, and it needs asking about directly, since a spillage weeks earlier is not volunteered. Open the connector and look rather than testing from the ends — green or white deposits on the pins are conclusive, and no resistance measurement is as fast. Cleaning is rarely enough where the residue has wicked into the loom; the affected section usually has to be replaced, which is why this often returns after an apparently successful repair.