Spot light wiring on XK140

I am currently trying to figure out how to wire an aftermarket light switch (4 position). I have found 2 different diagrams for the same switch. Although different, they essentially perform the same. I am good with sidelights only; Sidelights and Headlights but when I get to position 4, the headlights switch off as the spotlights come on.
Is this the correct configuration? are headlights & spotlights not able to operate at the same time due to current constraints within the switch.

Appreciate you help

Stuart, its a LEGAL requirement (in all developed countries) regarding how auxiliary lamps are Switched.
Jaguar NEVER offered Spot Lights/Driving lights as original equipment on any XK.
But Foglamps were offered as an option on XK120s, and standard or optional on XK140/150, but the law requires Foglamps to be switched differently to Spot Lights.

The standard Lucas four position switch as used on XK140 with Foglamps fitted, works as you say. - so position four when foglamps come on still with side lamps on disconnects the headlamps circuit.

I am told by others who have tried to use this four position switch that if bridged to have spotlamps on with the headlamps on, you will burn out the switch not being rated/designed for such high current draw. You should be able to run a separate circuit/switch for your desired spotlamps, albeit not legal, or probably bridge your four-position switch via a relay to operate your separate spotlight circuit, but still be careful re rating/fuse of circuit you bridge…

Lucas may well have made a suitable four position switch to suit auxilliary spot lamps, legally switched and appropriately rated, but still you need to check rating implications on your XK140 circuit/fuse you wish to use…

Hi Roger

Thank you for your feedback. Looks like I need to start thinking of these as fog lights that function as per the switch.

Much appreciated


Fog and spot wiring diagram.pdf (544.4 KB)
Here is a diagram of the way I have wired up an XK 120 (which only has the 3 position light switch so a four position switch will be slightly different).
However there are some principles which apply and so I hope this diagram gives some ideas about the rest of the circuit, which takes into account that the spotlight only works when the headlights are on and the fog light only work when the side lights are on.

That’s quite a piece of work, Thank you

Excellent diagram.
And if you really want to be authentic period, a Lucas relay.