Yellow is actually permanent live (red is switched). Run a new one with decent gauge cable (about 12AWG should be fine) straight from the battery. Make sure you use an inline fuse near to the battery (can't remember how much current these units draw though, 15A should be about right, 10A would be better though if they don't draw more than that). Alpine actually recommend you do this anyway with their higher powered headunits if you plan to use the internal amps on them.
