77 superglide. Press turn signal button',rear signal will light brightly,but other three turn signals will come on dimly. I have gone through all harnesses and disconnected signal buttons,kill switch,and start button.also went around flasher,but still no change.Left and right side do the same thing. I know I had a short some where because it melted my throttle cable lining from a bare spot on the cable cable housing touching the frame.

 

Bite the bullet and rewire!

 

Sounds like a bad ground. I would check them B4 rewiring.