XJ6 Headlight Wiring


New member
Nov 1, 2020
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Toowoomba, Queensland

I've been looking into a bit of a headlight issue I'm trying to wrap my head around.
From what I've read everyone meets Lucas the prince of darkness at some stage of Jaguar ownership.
I've completed the recommendations on this page, including cleaning and checking fuses of my right hand drive 1984 XJ6.

Originally only one side (drivers side) was working (outer and inner light with high beam flash operational). After playing around with the wiring and copying the layout of another car I can get all outer lights working but my high beam flash nor the inner smaller headlights are working. I can hear the Hella Relay click when I operate the flash stalk once, then it won't work afterwards. I have opened the relay and it appears to be operational - no melted parts or anything.

Instead, if I move the interior headlight switch to the 3rd position I can get the high beams to go on but get a bulb error on the dashboard.

I have attached photos of the wiring from the current setup, the wiring of a donor car and the interior headlight switch. I have also checked the wiring diagram but I can't read it in terms of what happens around the front inner fender fusebox.

Fuse 1: thick blue/white wire - two thin blue/white wires
Fuse 2: thick blue/red wire, thin blue/red (connects to fuse 4) - thin blue/red wire
Fuse 3: thick blue/white wire/thin blue/white wire - thick blue/white wire
Fuse 4: thin blue/red wire (connects to Fuse 2) - blue/red wire
Fuse 5: brown wire - brown wire

Position 0: off
Position 1: outer standby/parking lights
Position 2: outer standby/parking lights
Position 3: outer high beams (and error on dash)

The question I have is, what is/should be the correct wiring and the operation of the interior headlight switch be?
At what position of the interior headlight switch should the inner head lights turn on?



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Pete M

Aug 30, 2019
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Oxford, Canterbury, New Zealand
Hi lownslow,
I haven't seen a headlight switch with those positions on, but my guess is that they are: 1 - off. 2 - side or park lights only, 3 - side lights and headlights low and high beam. 4 - side lights and low beam headlights with rear fog lights on, 5 - Front Fog lights.
My car doesn't have fog lights, but I have done some work upgrading the headlight units. Your pic of the front headlight fuse box shows that this has been upgraded at some stage, as the standard fuses are circular, not the blade type. The headlight relay is a standard part and should be simple to source and try it as a replacement. You could put 12v onto the outputs of the relay to see if the relevant lights operate.
I have attached a pdf from SKJagtech, which gives a colour diagram of the XJ6 wiring, divided into relevant circuits for clarity. The standard Jaguar one is a bit hard to follow. I hope this helps.

Pete M


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XJ for two

Apr 23, 2007
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that is the European headlights switch. The switch uses the same wiring plug as the rest of the world, they just have a few more positions.

the poster needs to test the headlight in question directly from the battery, if it lights up, then the unit is good.

if the 4 headlight fuses are fine, I would still replace them, you never know. If the Relay clicks and it has the Red Resistors, it is good.

why would the wiring to the headlight itself be messed up? Has it been messed with ? The wiring is pretty basic: one wire is GROUND/EARTH, one wire is 12 volt to low beam, one wire is 12 volt to high beam. If there is a fourth wire, it is for the small parking bulb, and that wire needs to connect to the parking lights wiring which obviously the wiring harness would have.