I bought this Volvo S80 , i knew it had issues but couldn't resist not to buy it , haven't own a Volvo in 5 yrs . here goes the issue ....Trunk lights would not turn off. When I disconnected them, battery drained due to some unknown cause although everything was turned off . what can i check ?

 

You need to check trunk loom.
There is also issues with trunk panel with open button and lighting.
There can be shortage inside.