few issues with trucks stereo and wiring

[OlBlue1990]

recent purchased my ranger. the PO had swapped in an after market head unit before i got it. it seems to be installed correctly from the naked eye, they used the adapter you get at the store, and everything has tight connections. the problems are this-


after install, its created a battery drain. itll kill a fully charged battery in about 8 hours. PO installed a kill switch to 'solve' the problem. i got the truck, and found out that the radio was the culprit of the drain. pulled the dash, quickly looked at the wiring and then unplugged the stereo from the wiring adapter. it fixed the drain for now, but i know itll start up again once its getting power. fuse is good btw, first thing i checked.
id prefer to have some sort of idea of what im getting into before i tear about the dash here in a couple days if it cant be solved otherwise.

has any one ever experienced something like this before? and how do i go about fixing it.

 

[RangerSVT]

Sounds like its either the way the radio is wired to the adapter, or the radio itself is the problem, if when you unplug the radio the problem goes away...

SVT

 

[OlBlue1990]

yeah, i pulled the radio fuse at first and it took away the drain.

then put the fuse back in, and disconnected the stereo from the adapter. its just sitting in the dash right now. im gonna guess its the head unit its self, its outdated anyways.