Xantia S2 Headlights

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DickieG
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Xantia S2 Headlights

Post by DickieG »

With the dark evenings now upon us and the recent thread about fitting relays to the headlights on S1 Xantia's, I decided to measure the voltage at the bulbs on my S2 to see whether there was any noticeable voltage loss. Its generally accepted that S2's don't suffer from this problem but what I discovered rather surprised me as the voltage was around one volt lower than the battery voltage, when I bridged a separate wire directly from the battery to the back of the bulb the voltage improved by 0.9V which may not sound like a lot but when it comes to bulb output its a significant loss.

Even though I did this test in bright sunlight the difference in brightness was obvious to see whenever I touched the back of the bulb with the lead from the battery, needless to say I'll be fitting a pair of relays to overcome this issue in the very near future.

For a very good link on the subject explaining the light loss compared with voltage drop including a wiring diagram for fitting relays click here.
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Re: Xantia S2 Headlights

Post by Xaccers »

Definitely worth doing Richard.
You did the mod on Jim's didn't you? With the wires through the bulb access panel.
When we dids Cassy it looked like there would be enough space to drill through the base of the headlight, which apart from having to remove them from the car to do it, would make it much tidier.
Might do that when I do the mod on Jenny.
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Re: Xantia S2 Headlights

Post by DickieG »

Xac wrote:Definitely worth doing Richard.
You did the mod on Jim's didn't you? With the wires through the bulb access panel.
Yes I did, the difference in voltage on that Activa was a whopping 1.5V pre and post relay, the difference in light output was very significant.
Xac wrote:When we dids Cassy it looked like there would be enough space to drill through the base of the headlight, which apart from having to remove them from the car to do it, would make it much tidier.
Did you go through the underside of the headlight or is it a case of you thinking they'll be enough room for your next conversion?
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Re: Xantia S2 Headlights

Post by Xaccers »

I'll be looking into it fully next time.
With Cassy I trimmed back the sheath on the connector and spliced the relay into the orange wire.
There was a drop of about 1V, but with the corrosion on the end of the main positive feed from the battery terminal, output voltage was less than 13V to start with!
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Re: Xantia S2 Headlights

Post by jgra1 »

I did mine a couple of years ago.. just used some thick cable (15A I think) from the battery terminal to two relays, one for dip and one for main. Also carried thicker Earth wire..
I think me being me, I just left the headlamp backs off ;)
with better wattage main beam bulbs, and self - realigned headlamps, I am almost happy..
despite the dips being where I think they should be, the OS main is pointing at the road just below it!..
Will have to try and align that on it's own, with the headlamp flash on and the nearside light covered up.. bit wierd though..

:) J

edit (used an inline fuse for dip and one for main, but may change that after reading Andy's post below)
Last edited by jgra1 on 02 Nov 2011, 16:08, edited 3 times in total.
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Re: Xantia S2 Headlights

Post by andy5 »

DickieG wrote:
For a very good link on the subject explaining the light loss compared with voltage drop including a wiring diagram for fitting relays click here.
I'm not sure I like that scheme. He's simplified things by not depicting the existing fuses, and from the written description they don't seem to be mentioned afterwards. Yes, there's a supply-side fuse, but I believe that there's usually a fuse for each lamp, and I think that would be something well worth keeping, so a short circuit at one lamp doesn't switch off others.
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Re: Xantia S2 Headlights

Post by Dommo »

Is the original wiring still in place though? If it is your lights would surely still work, just the voltage will drop to the original loom voltage?
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Re: Xantia S2 Headlights

Post by jgra1 »

yes Dommo, but that means stopping and getting the torch out and changing it all back over.. wouldnt take long, but no use mid bend at speed :)

I guess that was Andy's point?

I suppose you could just use the main beam if the dipped went? I have not seen the diag, so I dont know if one fuse is for all 4 lights, or there is a fuse for each pair...


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Re: Xantia S2 Headlights

Post by CitroJim »

I strongly agree the relay mod is good... Richard did my Activa when he owned it and the lights are like a pair of HIDs but without the disadvantages...

We saw a vast improvement when we did Xac's Cassy and its not really a difficult job. The feeds to the relays MUST be fused though. That's essential...
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Re: Xantia S2 Headlights

Post by andy5 »

Dommo wrote:Is the original wiring still in place though? If it is your lights would surely still work, just the voltage will drop to the original loom voltage?
No, the new wire is not in parallel with the old, if that's what you are asking. That was just the brief test mentioned to see if it was worth changing. When rewired, the original wire, via switch and dipswitch and fuse to headlight, is used only to switch a relay coil, and a contact on that relay switches the chunkier new power line.

What I'm getting at is I believe there are currently fuses per light, which that article has omitted to discuss either before or after the modification, so it's over-simplified things.

Edit, to clarify, this was the article DickieG linked to, which I'm waffling about
DickieG wrote: For a very good link on the subject explaining the light loss compared with voltage drop including a wiring diagram for fitting relays click here.
As that stands, or as I see it anyway, in the new version, with its dual beams and all four mains in parallel, a problem at one main beam would mean the fuse by the alternator goes and all thus four main beams go off. Same for the pair of dips, one off both off.

And although it seems far fetched for a fuse to spontaneously go, things like that do happen. I've found it's not uncommon for old household bulb filaments to short out as they finally melt and collapse, and blow the fuse in the plug. And I've had it once or twice on a car, new bulb and it's still not working, check the fuse.

So I think I'd like the fuse he has as near as possible to the battery or alternator, plus another fuse per light between relay and each light.

The example in the article has twin filaments on the one pair of bulbs which switch dip and main, then just mains on the inner pair, like the H4 + H1 in the old Rover SD1 I had years ago, so you could say there are actually 6, whereas the Xantia has 4 X H1 single filaments.
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Re: Xantia S2 Headlights

Post by DickieG »

I started fitting the additional headlight relays to my HDi this afternoon and finished the N/S one before bad light (and a sore back) stopped play :lol: As the original bulbs each have their own fuse I took a separate fused supply from the battery for each light which also has its own relay, I did this working on the principle that even though I'm using substantial 17.5amp cable putting two bulbs on the one relay could lead to overloading the cable as the original layout uses a 10 amp fuse per bulb. This method also addresses the point made above of one fuse blowing and losing both headlights.

I did try connecting onto the new relay fed supply onto the original headlight connector just outside the headlight but this method loses about 0.15V so I used Xac's tip and removed the headlight to then drill a small hole on the underside of the headlight to feed the new supply wire directly onto the back of the bulb.

End result is an additional 0.95V on each bulb, or more importantly the bullbs were only operating at around 70% efficiency compared with 100% now.
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