The Headlights Switch in the Series 3 XJ-6
and XJ-12 built from 1979 to 1987,
and fitted to cars sold in America,
can be replaced with the Headlights Switch
fitted to European cars of the same years.
The European switch is a direct-fit for American cars, no modifications to the factory wiring is required, it's plug 'n play.
Why do this?
the UK switch has more On-Off combinations than the American switch, and it allows you
to use your auxiliary lights,
(Fog or Driving), at the same time the Headlights
are ON, contrary to the American switch that turns OFF your headlights when you select
the Fog or Driving lights position.
you can source this switch from the UK,
it is not available in the US.
The pictures below show a comparison
of the American and European switches.
In my car, I installed a pair of twin Fog and Spot lamps
which are switched from the UK lights switch.
The Fog lights (yellow) are wired as normally to the factory wiring harness.
The Spot lights (white) are wired to the Rear Fog lights position
of the UK switch, which the US switch does not have.