Direction of the tap is very important. Also when tapping a fuse in the BJB (battery junction box). Another point to note is the original fuse size (amps) that your trying to use.
If you're attempting to pull 15 amps from a 5 or 10 amp supply bad things will occur. Tell me what you need. Constantly Hot, Ignition Hot? If you're really in need of higher thought put be need it switched Ignition Hot then you can always add a fuse to the HVJB (high voltage junction box) and put a relay that can be triggered by the Ignition relay output.
Just let me know.