Default HTC M7: Wifi stuck on "searching", device is hot, battery drains.

my device suddenly got hotter - the battery drains really fast, like 10% in few minutes on IDLE .
did a Factory Reset - didnt helped.
the Wifi is stuck on "searching mode" after the reset and before it.
i turnd the phone when it was 40% battery, it was still hot - WHEN TURND OFF!
turnd it on again after 30 minutes - the battery was 1% and the device went down.

its the original ROM 4.4.2 - not rooted!

what do i do? \=