water damage galaxy s3 help me please!

i have a galaxy s3 that has been water damaged for a good 2-3 months , but one day i decide to take a look at it and the fone turned on just fine only for a few min , so i took the fone apart put rubbing alcohol and when that was done , it didnt turn on but when i put the battery to freeze and try to put it back in the fone it turns on for a few more min.. do you have any solution on how to solve this ? everything on the fone works well .. it turns on and everything but the screen remains black they keys light up just fine