S2 xj6L no main beam headlights

It was an article on the old website, I’ll check it again maybe I miss read it. I thought it was saying the dipped lights pass into the hella relay but only main beams are tripped by the relay and if you want to ditch the sealed beams another relay is required. There was a diagram showing the wiring and additianal relay.

Well done, Dennis,

most electric issues are not very expensive, if you give enough of your own time and patience!

As for your new project: indeed, when headlight power is run from the alternator through the headlight switch and to the headlights there is high load on the switch and on older cars all likelihood of power losses.

And yes, our cars do use that kind of wiring. OTOH, as long as you measure happy 13+ V at the blue wire with the engine on and your light switch doesn’t get hot you can spend your time better I guess.

I once had a car with a 6V system and only 4.2 V left at the main lights … that was really dim and a relay with new fat power wires were definitely called for. I doubt your Jag will need it.



75 XJ6L 4.2 auto (UK spec)

I’ll probably leave any further upgrades for now Jochen,
I have done a lot of work on the car this winter and will put some miles on it now.

The article referred to a different set-up from yours, Dennis…

In ‘our’ case both ‘high’ and 'low beam power goes from the main light switch brown via the blue, ‘headlamp position’, to the relay. The relay is switched from ‘high’ to ‘low’, or ‘low’ to ‘high’, by the stalk switch grounding the relay. The current here is very low, and require no relay…

Some do indeed introduce relays between the relay and the fuses/headlamps both to reduce power loss through the long wires - and to reduce the current going through the light switch and relay. However, both are dimensioned to take the load - and the complication of extra relays may be an arguably advantage…

Incidentally, with the light switch ‘off’; holding the stalk switch will light up ‘high’ beams - the ‘flash’ function.

That said; the kudos for fixing the problem is negated by your own action of disconnecting the brown without reconnecting it - but well done in any case…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

Gotta brag a bit. My earlier post suffested the firewall post source of the always hot that was lacking

simple solution. The best ones…



You hit that nail directly on the head yet again. :slight_smile:


Can’t beat some 70+ years of experience, can you?

Keep that spirit


75 XJ6L 4.2 auto (UK spec)

Thanks for the clarification regarding the lighting relays Frank,
Good to hear I can leave them as is, and of course your right no kudos for my forgetfulness. The only reason I found and fixed the issue was through the info posted here.


Thanks for your correct suggestion Carl,
It sure helped the guy with cotton wool between the ears :blush:

There is “think” and “over think”. Decide which to pursue.

My former profession n helped me a lot. analysis of information a key to my job.

In this case. the “brown” should have volts. It does not. Where is the source of those volts? Hot posts n the fire wall! check them out!

As to relays, not to confuse the issue. That is the issue that no longer exists. Past lister Alex Carnara designed a circuit with a relay to “help” the Hella relay provided by Jaguar to feed the main lamps.

Decades ago in the 6v car era, an after market kit was sold to boost lamp brightness. Two relays in a tin can. One for brights and one for dims. One helped my 37 Ford a lot. Yet, revving the engine was useful in very dark areas!!

My German born wife was enamored of baumwolle, burt not of mere cotton? She was astounded when I pointed out that baumwolle was in fact cotton. Not from a sheep but from a plant, ie baum…

I delight in words and phrases. Cotton between the ears as a phrase will stick with me.


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