batery blowing 12v rail to deck
To test outside of the car, use a 12v battery or power adapter with enough amperage to at least turn on the radio (which doesn't take much really). If you don't have either of those, two 6v lantern batteries in series could work.
Usually the radio will also have a fuse on the back so check that too. Also, for testing fuses, use a multi-meter on the continuity/beep setting instead of visual inspection.




