Headlight switch backlight dimmer blows horn fuse...???

Caco2120 said
1974 scamp.
High and low beams work.
Blue indicator light works.
Horn works.
Turn signals and indicators work
No backlights at any time (they are newer bulbs)

Turn the dimmer knob
Horn fuse blows

Dome light works also on the door open switches. Does nothing with the knob twist .