Why green led light keep on Samsung S4

Hello guys Ive got issue with my Samsung S4. The green light keep light. I bought it from my cousin. He didnt have this issue. Once Ive got this phone I make factory setup, software upgrade and fill up the battery while night and from that moment is there that stupid green light. I though that is just because of jack for earphones because was broken but I order new one replace it and is still there. I tried install apps as light manager and others but nothing happens. I also tried get the battery on 0% until that led goes off take battery off and this help like for 5 minutes. I also tried disconnect usb port from motherboard and get back battery once I give there battery green light come back. Also the phone is overheat at the place where is motherboard. However the phone works well. Anyone resolve this issue ? What can be wrong ? Mothetboard, USB port ? Battery ?

Thanks for any help
Best Regards
Rasty