Elmas Xantia V6 and Musical Stuff

[CitroJim]

Mind you, I was never impressed with the C1's either...

A C1 doesn't go fast enough to need headlights. A bike lamp would do [emoji12] [emoji23]

[Hell Razor5543]

Mind you, I was never impressed with the C1's either...

A C1 doesn't go fast enough to need headlights. A bike lamp would do [emoji12] [emoji23]

Sent from my SM-G361F using Tapatalk

The biggest problem is with all of the moths converging on the light!

[CitroJim]

Mind you, I was never impressed with the C1's either...

A C1 doesn't go fast enough to need headlights. A bike lamp would do [emoji12] [emoji23]

Sent from my SM-G361F using Tapatalk

The biggest problem is with all of the moths converging on the light!

Yes, absolutely!

[xantia_v6]

Do RHD Xantias have the same internal plastic fresnel lens on dip beam that XMs have?

Very early S1s do Chris...

I believe they were updated to have no Fresnel lenses in around 1996 when the S1.5* Xantia came along... I understand they did update the XM variant as there was not enough RHD demand to warrant it

I believe that bleaching the Fresnel lens in an XM if it has discoloured to a yellowish tint can make all the difference...

* My own definition - never an officially recognised variant!

I must say I find S2 Xantia headlights worse than relay-modified late S1 variants...

The Xantia was never fitted with the internal Fresnel lenses (of XM style). Early RHD Xantias (until some point in 1995) did have a different Fresnel pattern in the glass lens which spread the light more, leaving less for straight ahead. I have never seen a LHD Xantia with the early style lens, so maybe it was RHD-only?

Having owned a few Xantia V6s, I would say that they all needed new bulbs, but even then there was quite a variation between the illumination of individual headlight units. I think that dirty film on the reflector is a big culprit, but the aluminised coating on the reflector rubs off very easily, so you must be very gentle when cleaning them.

[CitroJim]

I know it was a long time ago Mike and memory can play tricks but I'm as certain as I can be that my first 1.9TD sinker had Fresnel lenses. I do know the lights, even with Nightbreakers, were bloody atrocious and my next S1 with the later lights was much, much better... The change must have happened very early in production... Mine was a very, very early one - just four months into production... The reflectors were perfectly clean too...

[white exec]

I wonder if we're left with an inherent problem with limited-height reflector headlights. Most of the headlights we're concerned with, and most of their contemporaries, use exactly the same 55W halogen bulbs, whether H1, H4 or H7 - all essentially the same, filament- and bulb output-wise.

All these bulb assemblies are fitted with the same type of front-end light baffle (a metal plate, ahead of the bulb) to prevent forward scatter and therefore dazzle. This light baffle is often not particularly well-designed when it comes to reflection: it's often made of grey-plated steel. As such, it isn't particularly good at returning 'unwanted' forward-emitted light back towards the main reflector.

The forward projection of the light is mainly performed by the chromed reflector, and I have mixed reactions to this. When designing a spotlight reflector, the most effiecient shape for a point-source filament is circular in shape, and parabolic in profile. With a perfect one of these, the beam produced would be a perfect parallel-sided circular beam. Examples of these have been anti-aircraft spotlights, and even the humble pocket torch.

No-one in their right mind would begin to design a spotlight reflector which was heavily rectangular to the point of almost being a slit. The geometry of such a narrow reflector just works against optical efficiency. Although, in theory, there is no "lumens limit" to the quantity of light that a small reflector can cope with, few optical physicists would choose such a narrow and rectangular shape.

It also doesn't help that only a limited portion of the internal headlight space is filled with useful reflector. The outer-edge 'strips' don't bring anything much to the party - again the consequence of shape and angled glass.

It is interesting to conpare the light output of BX and XM. The deep rectangular BX headlights were outstanding (and designed without use of computer analysis), and provided outstanding evenness and level of coverage.

To further shape the beam, the headlight glass needs to act as a directional lens (it's a fresnel design) and to provide "shuttering" to prevent dazzle in specific directions. This takes the form of a closely-spaced ribbed patterning of the glass, so that hot-spots on the reflector are not seen by oncoming traffic. All this glass patterning further reduces the light output of the headlamp, and the smaller the glass area - and narrow headlights are already a bit short of glass area - the more the output is attenuated. The steep rake of the XM front glass likely attenuates the light output even more, by effectively presenting 'thicker glass' to the exiting beam.

Looking back a bit, but staying with 55W halogen H4/H1, both Cibie and Hella (particularly Hella) produced some stunningly good 7-inch round headlight units, as well as a slightly smaller 5.75-inch version. These put earlier Lucas units to shame, even when using the same bulbs. VW and BMW vehicles lead the way. A four-headlight vehicle could provide something akin to daylight on main beam, and an extremely bright and even dip coverage.

Unfortunately, illumination-wise, styling got the upper hand, and the XM headlights got pretty damn narrow, although some went further.

Given what we have, the only real options are
- clean up the internal fresnels (only fitted to RHD) on the XM
- carefully clean the chromed reflectors (the plating is easily buffed off, unfortunately); rechrome?
- use the best halogen bulbs available
- optimise wiring and supply to the bulbs (better wiring, relays) and clean up contacts
- wait until technology offers a genuine 'point source' H1/H4 replacement, whether HID or something else (all the existing offerenings have drawbacks, and are not designed to work with our light units)
- consider higher wattage H-series halogen bulbs (not street-legal, and issues surrounding wiring, switching and heat). I think use of Nightbreaker or X-treme bulbs provide a better solution here, from several points of view.

There are some oddball approaches to the XM dip-beam situation. When moving to Spain I acquired a pair of new LHD headlight units, which always did operate without internal fresnels. Good news, but bad too. I found that dip beam consisted of two very bring pools of light just ahead of the car, and not the even spread of flat-top 'apron' that a good dip beam should offer. To cut a long story short, I re-installed the original RHD light units, but flipped the internal fresnels to give the LHD pattern (kerb kick-up on the right). The result is very good, for LHD purposes, and satisfies testers here.

As has been said, keeping the internal fresnels clear and free from noticeable yellowing is a big improvement. I have concluded that the yellowing is the same which plastic headlights (and light-coloured plastics in general) suffer from: exposure to UV causes the yellow-brown bromine compounds in the plastic to come to the surface. In the case of the clear fresnels, this can be largely polished off with Mer, T-Cut or the like. Turtle Wax plastic headlight restorer does the same, but no more effieciently. It would be good to get these fresnels remanufactured, of course, but this has been extensively discussed before.

Top-quality halogen bulbs also have effective UV-block built into their glass, which helps keep these fresnels clear. Not a lot of help in the Xantia case, though.

[xantia_v6]

Two corrections for the above:

LHD XMs had the plastic internal lens until about 1993.

, headlight reflectors are never chromed, as chrome is not a good reflective surface and actually absorbs light (chrome plated items are always chrome plated over nickel plating and it is the nickel which is shiny).

Headlight reflectors until the 1940s were silver plated, which works well, but the silver tarnishes over time, reducing performance. To get around this the Americans designed the sealed beam headlight which had the reflective surface inside an inert environment. Then silver was replaced with vacuum deposited aluminium, which is still the usual reflective surface.

This wikipedia article is interesting, and (I think wrongly) attributes the Citroen XM of having complex-reflector headlights.

The internal plastic Fresnel lens of the XM was first seen in the Cibie headlights on the 1975 Jaguar XJ-S which was I think the first to use such things (Valeo own Cibie). Jaguar dropped the internal plastic lens design in 1981, only for Citroen to make the same mistake a few years later.

I believe that the Xantia Mk2 optics are identical to the late Mk1, the lamp shape and lens were only changed for cosmetic purposes.

[Stickyfinger]

Having now taken apart and totally messed about with 6 headlamp units, I would add only this, NEVER even try and touch the silver reflective surface with anything (not even a duck feather !), only blow clean it.

Forgot.....also never wet it.

[Zelandeth]

Jim, quick heads up to save you a few quid, Gabriel has Night breaker Unlimited lamps in the dip beam position already, fitted pretty recently from memory (as I tried some others briefly which were pants). Mains are due a change though I think.

Worst headlights I've experienced in a car were an early Fiat Panda...no halogen lamps there...worst overall were on a Leyland Tiger based coach...they were useless to start with, then turning on the saloon lights and the whole outside world vanished!

[daviemck2006]

That was a problem on some elderly coaches. Crap headlights, even though a lot of them had twin headlights, and the saloon lights on so all you could see was the whole length of the coach reflected in the windscreen! Happy days lol

Sent from my SM-T705 using Tapatalk

[CitroJim]

Chris and Mike, interesting stuff in your latest posts on the light subject

Jim, quick heads up to save you a few quid, Gabriel has Night breaker Unlimited lamps in the dip beam position already

Thanks Zel That is excellent and will save me a few pennies not to mention a few skinned fingers swapping bulbs

[elma]

The electric seats are now fully functional, it was just dirty contacts The scratch pen Jim recommended was excellent. Moving on now to the leaky solenoid and measuring the coolant bottle.

[Stickyfinger]

Inside the expansion bottle



because a pressure test showed this


The white "dust" is talc.....used to disclose any damp patches, as you see the leaking was slightly more that expected...

[superloopy]

You own THAT much talc Sticky .... cant remember. the last time i actually saw any, not even at xmas time. Now thirty years ago, yes, there it was every year. You must be a hoarder [emoji1]

Sent from my LG-D855 using Tapatalk

[CitroJim]

The electric seats are now fully functional, it was just dirty contacts The scratch pen Jim recommended was excellent.

Excellent news James Delighted to hear it...