Headlight Plastic Lenses, Which way do they go?

A while ago when I had the bumper/nose-cone off I decided I would try taking the plastic lenses out of my headlights to see how it was. As with some others I decided I didn't like it - the beam is too narrow so it doesn't light up enough of the road. Yes it is a bit brighter, but that just makes it worse because there is more contrast with the important bits of the road that aren't lit.

So, I want to put them back in. But, like a complete fool, I forgot to make a note of which way round they go

So... Looking at them they both have the same pattern, but the shape/outline is a mirror image due to the shape of the light.

There is a smooth and a cut/ridged side to them. Which one points outwards?

Either the top or bottom has fixed tabs, and the other has 'sprung' tabs. I hope you know what I mean. Which goes upwards?

I think those 2 answers should allow me to get them in the right way without any ambiguity.

Hi rowanmoor, there is a page i came across somewhere showing the fitment of the inner diffusers,have been trawling through my files, but can't find it.However, for R/H drive the smooth surface is placed inwards(rearwards, towards the bulb) and for L/H drive the smooth surface is placed outwards(forwards, towards the outer lens).

Hi all. On this general subject of the lenses, has anyone found a supply of new ones to replace the yellowed units?
Ta Robin.

Thanks, that solves half the puzzle (and explains the LHD/RHD side of things too).

The other question is whether the springy tags go top or bottom? Though that may be obvious from the shape when you put it in the light... I didn't look closely enough at them to be sure how symmetrical (or not) they are.

Hi again, yes it will be clear when you reinstall them, in order to fit them with the smooth surface facing inwards for RHD, they will only fit one headlight as the the edges are not parallell,the spring tabs are always up,hence for LHD you transpose them from o/s to n/s.And Robin, citroen do supply the lens for the mk 1 (it is the same one as for the mk2 i think) but don't list it for the mk2. P/N is 621353 and £36 each!!!

This post has been edited by robertmnorton on December 10, 2008 09:13 am

Thanks. Now I just need to find some time to do it on a day when my fingers won't freeze before I have got the sidelights out.

I seem to remember reading somewhere that the lense was redesigned for the Mk2 but due to high mould set-up costs only Modified LHD ones were produced. The original Mk1 RHD ones being used throughout XM production. As far as I can see the reflector shape is the same for both of the XM lights so I would expect the LHD and RHD lenses to be mirror images of each other and designed for the flat side to be one way round only. Fitting the lens rough side inwards would fractionally increase light scatter but that would only be significant to the purist who designed the lense system. So I suspect that Robert is right that fitting the RHD lense the wrong way round gives you a near perfect LHD headlight. The yellowing of the lenses seems to be variable so maybe caused by exposure of the plastic to UV light. It seems to have a particularly bad effect on the wavelengths of light given out by most common Halogen bulbs. I suspect that Citroen changed the plastic spec for the Mk2 version to overcome this problem. I have noticed that HID light output at a different wavelength does not seem to be affected by the yellowing of the lense.

John

This post has been edited by xmexclusive on December 10, 2008 11:42 am

Hi rowanmoor, finally found the repair manual page with regard to inner headlamp lens's.