Main fuse.... power to main fuse and zero on the red wire @ ign. switch = main fuse. The fuse element is 'prolly broken under one of the caps where you cant see it ( caused by old age/vibration over 40 yrs ! ).
And/or corroded fuse holder. The fuse clips must be shiny brass colored or no good and each clip must grip the fuse tightly. The other 2 fuses are not 'live' until you switch 'on' the ign., so normal
