It's not a silly question at all.CrypticG wrote:Apologise for the maybe silly question..
How come Xenons require a self-levelling system? What does this add or bring to make them legal?
Where does it go and what is it?
I have headlight washers so that shouldn't be an issue.
Basically, two sensors are fitted to the from and rear axle, and these determine the loading of the car when the ignition is first turned on and the lights automatically adjust to set the correct height. The intention is to ensure the xenons, which are incredibly bright compared to halogen bulbs, do not dazzle oncoming drivers too much. Eg, if you have two guys in the back, with some luggage in the boot, the car will be nose up, so the system points the lights down a little.
It doesn't dynamically adjust the lights for bumps and undulation, which is why you will still see the beam cutoff going up and down whilst driving, but that's the same as any other car.
Cars fitted with self levelling don't have a level adjuster in the car by the light switch, the system takes care of it.
MOT testers are supposed to check for self levelling function on xenon equipped cars, along with headlight washers, the latter are easy to check for and their operation, but I understand they are allowed to give the 'benefit of the doubt' with regard to the presence of fully functioning self levelling as it's difficult to check at the MOT station.
As long as the lights are correct set/aimed, they would pass if the washers are working most of the time. I know it's a developing area of legislation, the authorities get a lot of complaints about it and they are slowly but surely tightening the noose around aftermarket systems.
