Water damage no display

Tom R, bad display or bad backlight filter/circuitry. Open your iPhone by using these guides. Clean the whole phone with a high grade (90%+) isopropyl alcohol and a soft brush to clean it. Here is an excellent guide on how to clean an iPhone. It was written for a 3GS but all the steps are still pertinent to your phone as well. Once you clean it properly , I'd suggest to replace the battery as well. Humidity etc. can cause to battery failure later on. While you clean pay particular attention to the small components around the display connector. Check for corrosion, visible damage etc. Replace the display if it still should not work after properly cleaning it . It is a lot cheaper and easier than doing some board level repair which would be the next step.