Water damaged iPhone 4 only starts when on mains charger ?

Just had a iPhone 4 given to me that had been water damaged I’ve taken it all apart and cleaned it with 99% alcohol and put it all back together, the phone now comes on but only when it’s plugged in to the mains charger has anyone else had this problem ?
Answer #1
Stop[ using it .. U might Blow it up.
Open the insides… let it dry out in a warm place preferably in the sun.. put a dust cover over it for a couple days.
Answer #2
Make sure the battery connectors and contacts are all clean.
Does it indicate charging when plugged to the mains?
Try a new battery.
Answer #3
Thanks I have tried a new battery and same problem, have tried cleaning it again so hopefully that will work
Answer #4
Turn it off… put it in a bag filled with uncooked rice for 24 hours… the rice will draw any moisture out of the phone and you should be good to go from there.