first thing you want to do is to stop using your controller and no longer plug it in. remove your battery. disassemble your controller and clean every parts with a high grade 90%+ isopropyl alcohol and a small brush. Check for burned out or missing components. Once you ensured it is clean, '''replace the battery and reassemble your Dualshock. then re-evaluate and see what you get. Water damage is the toughest to troubleshoot and to repair, so let us know what you find. Hope this helps, good luck.
I had a similar problem , my 1yr old son threwmy controller in the mop bucket, it wasin there for almost a day.. when i took it out water came out from everywhere.. i let it dry for two days . Then i plugged it . . The red light came on for one second then turned off... so i decided to open it.. (youtube open controller ). Then i unplugged the light, and battery. . Put a blow dryer on it. On cool, not hot.. . And after 10 mins . Put the battery in, light in . And it worked. .. saved me 50 bucks.lol. hope this helps you out.
Ok so I had some spare pure alcohol left over from an iPhone repair. You can get it on eBay. I put the hole 100mill bottle in to the ring around the joy sticks and kept shaking it for about 15mins (aggressive shaking) then I put my girlfriends hair dryer on full power like Jeremy clarkson. Full power (cold) don't be tempted by hot it warps the battery casing. And it came back to life I hope it helps you guys/girls.