What to do if I drop my left joycon in water

@kaitlyntrout you will have to treat it like you would treat any other liquid immersed device.

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The very first step I would take, is to disassemble your Joy-Con. Use these guides 左側 Joy-Con 充電レールの交換 to help you disassemble it. Take a careful and close look at all components and connectors. Truly assess the damage. Look for major corrosion, evaluate the pins in the connectors etc,. Take a look at all connectors as well as cable ends. Once you got the gross contamination cleaned, use 90%+(the higher the % the better) isopropyl alcohol and clean your parts some more. For a proper cleaning, use this guide. It was written for an Apple iPhone 3G but it is still pertinent to your device as well. I can not stress the importance of a good cleaning enough, so do it over and over while replacing the alcohol after each cleaning. Do not use compressed air for the cleaning since that can drive liquid as well as corrosion particles into areas that will cause trouble later on. To remove any gross contamination, do not use drinking water. If you need to use water, use sterile water. Also, you do not need to leave the cleaned parts to dry. Isopropyl alcohol in the higher concentration will evaporate quickly and dissipate the water. The importance here is the cleaning. It would of course be best to get it professionally cleaned with an ultrasonic cleaner. Do not forget to replace the battery. This is a must and not an option. It will fail if you do not take care of it now. After that, reassemble your Joy-Con and re-evaluate.