I am looking for a wire that is only on when the key is on. like the radio to install an xm commander. I have a constant on wire found behing the dash that wasn't used for the PIe aux converter.
would it hurt to tie the xm radio into a line that is already being used?
would it hurt to tie it into a constant on power? other than making sure it is off when the key is not in, will it damage or drain the battery or blow a fuse? thanks

 

on my MY truck, behind the radio, the red wire was the one you want, the yellow wire is on all the time, my truck is a 2000 XLT