iphone 4s power on loop

iphone 4s water damaged light



changed battery still same



changed charger port still same



changed sensor flex still same



when power on with sensor/power button flex off not plugged then powers on charging etc ok,but when plug in flex goes off!



so phone can be use with no sensor/power button flex attatched



please any idea where to start



thanks

via Welcome to gsm-tips http://ift.tt/1neuXfB