The Lucas handle bar mounted horn button with headlamp dip was introduced to Triumph Pre-Unit in 1956. Previously the horn and dip were separate switches. The horn button was a threaded affair which screwed directly into the handle bar.


Lucas part number 31563 combined both functions but retained the lever perch mounting of the dip switch. The earlier lever clamp was threaded and used BA thread screws. Perch mounting of this switch was retained till 1965. From than on the switch was fixed directly to the handle bar with self tapping screws. We now offer a clamp on version which does not require screwing into the handle bar.

On all new production switches the color codes differ from the factory.

Here is the updated color codes:

Color = function (original factory color)

Yellow = power feed (blue)

Black = Head lamp Low beam (Red/Blue)

White = High beam (Blue/White)

Green = Horn (Brown/Black)