On my truck (all 6 volts) the siren-flasher has a flasher unit just for that purpose. The power comes from a new fuse relay ( That I added ) to a switch on the dash to the flashing unit and then to my siren-flasher. If you want your light to flash independently you will need 2 flashers units. One flasher unit could do the two lights but they will be flashing together.
Hope this help.
Lieut DGoss
