Hover over a wire to confirm the colour
2-wire Horns (pre-77)
The earth for the horn push comes from the body via the crossmember, rack, steering column U/J and column.

1-wire Horns (77-on)
12v via the switch and the horns pick up an earth from their mounting points. Relay option not shown for this as any bad connections should be relatively easy to solve, unlike the earth path of the 2-wire horns.

2-wire Horn Relay