How should I check the alignment of my headlights?

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veteran
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How should I check the alignment of my headlights?

Post by veteran »

Haven't had to do this for many, many years, so am somewhat 'rusty' on what the rules currently are.

Okay, I know that this can only best be done with specialist optical kit as used by MOT stations and dealer workshops, but I merely want to ensure that when my first MOT with this Polo becomes due, the headlights are set approximately correctly. Last year, for a specific and unrelated reason I temporarily took out one of the headlight assemblies, and also a 'friend' unfortunately fiddled with one of the adjusters on the opposite assembly, not realising what it was, so they're almost certainly misaligned at present.

Since first taking ownership of the car (1.2 TSI Polo Match Edition 6C), I have to confess I've not done a single night-time journey, so I have no idea as to the current beam patterns. I live in a cul de sac and have a convenient wall and some garage doors against/on which I can fix some suitable markers to denote the 'static' position.

In the UK, should the beam pattern be checked only on dipped beam, or instead high beam (or both!)? And what about the so-called 'sidelights'? Once I've initially marked out the centres of the headlight assemblies on the target (what I've called the 'static position'), how far away should I position the front of the car to see what the beam pattern is like and how my adjustments change it?

On my Match 6C there appears to be two adjusters per side, a large dished adjuster and a separate smaller one. Is the smaller one uniquely for the sidelights, or is this for lateral adjustment of dipped/high beam?

On both dipped and high beam respectively, and at the requisite distance, what is the maximum permitted distance allowed above the horizontal static position? For dipped beam, is there any permitted above the static position?

Any guidance you can give me as to where the right and left cutoff points should be would also be most appreciated.

This might seem like stating the blindingly obvious, but for members and other visitors to these forums who hail from the Continent of mainland Europe or further afield, do remember that this is for a Polo used in the UK and therefore is driven on the left side of the road, so if offering advice please ensure you define carefully what 'left' and 'right' are when it comes to describing what the beam pattern should look like.
ed.silmon-monerri
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Re: How should I check the alignment of my headlights?

Post by ed.silmon-monerri »

Hi. I'm a mechanic by trade but haven't worked for about a decade however MOT headlight parameters haven't changed much in that time, if at all, and for the polo 6c it's the dipped beam that's being checked. main beam will not be checked for alignment as it never has been though I think they must at least switch on/off properly but don't quote me on that.

The two different knobs on the lights control either the horizontal cutoff (height) or the diagonal cutoff. Turn it one way for one direction, the other for the other. It's very simple. I think the User Manual tells you which is for what; if you don't bother looking in it then remember how many times you turn the screws so you can wind them back if you're on the wrong one but look in the manual. You'll find something you didn't know! It's also much easier to see how much you're adjusting the headlight when the vehicle is further away from the wall, too so I'd suggest min 10m but better @20m.

I know of no universal way to do it other than simply going for an mot or to a garage with a headlight tester and asking/paying them to adjust them as at present there's never going to be a universal way to check correct beam alignment. The beam pattern for each car depends on the height of where the beam comes out of the headlights if you watch the MOT tester, they will move the lens box up and down to align it with the correct part of the headlight and this cannot be replicated with a wall and a piece of chalk, etc. and you need some maths that's not immediately available or particularly simple to figure to out anyway.

I suggest just eating the few quid, if they even charge you for it, when the time comes around. It takes 2 mins if all the adjusters are accessible which for the 6c polo they are. Ask before the test if you're really worried about cost then check with a few garages for their cost estimate (if anything!). The time you spend messing around can be better spent IMO and if you really have to, I suggest using the beam pattern of the headlight you took out and put back as unless you messed with the adjusters, there may be zero change from the factory setup which one assumes awas correct to begin with. The height is the most important and very easy to match. The diagonal you stand little chance of making correct at home which is why I suggest not bothering too much about it.

IDK if you use the electric beam height adjuster but bear in mind at the very least the "correct maximum height" must be set on number 0 which is the highest BEAM SETTING.
veteran
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Re: How should I check the alignment of my headlights?

Post by veteran »

ed.silmon-monerri,

Thanks for your thoughts on this. So, it's dipped-beam that needs checking, then? And one of the controls for each lamp assembly sets beam height, the other something you've referred to as 'diagonal cutoff'? Have never come across that term before. Twenty metres from the target surface. Okay, that's about 25 ft, which is a distance I've seen quoted in some YouTube guides, so that seems to fit.

My driver's manual does NOT give any guidance whatsoever on headlights adjustments. Clearly, VW prefers that you book the car into your local VW dealer, leaving your chequebook and a note saying 'help yourselves to whatever you need', for them to mysteriously then check the alignment out and set it up while you're not around. Sorry VW, with me that just ain't gonna happen.

I'm afraid, though, that I disagree with your contention that alignment cannot be done with any meaningful accuracy other than by using a professional beam-checker. In my view, if you follow a reliable DIY procedure for alignment, then you're likely to end up with it somewhere within the requisite tolerance. I wouldn't expect to be getting it spot on. All that the pro kit does is to make the process faster and much easier for the pro technician (especially since practically every marque/model of car has lamp heights and lamp separations that differ), checking for absolutely optimised alignment (as you say, based on near-touching beam-pattern measurement). But if, in the DIY situation, you set the optical centres of the lit headlight assemblies hard up against the target surface and mark them off (forming a horizontal line and the two optical centres) and then move the car backward by, say, 25 ft, then by the simple laws of optics/physics you should be able to see, via the 'magnification factor' of having moved away from the target, how much above or below the marked-out positions the right and left beams deviate. Some tolerances for the degree of 'above' and 'below' would have to be taken into account, especially on the 'above' illumination line (ie. the horizontal), as clearly that's where the illlumination should not cause dazzle to oncoming drivers.

Having found an increasing number of things that weren't right about this car after its delivery, I have little faith that the headlights were properly checked and set up at either the factory in SA or by the dealer here.
ed.silmon-monerri
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Re: How should I check the alignment of my headlights?

Post by ed.silmon-monerri »

I expect you should be able to set the horizontal aspect reasonably effectively by copying from another very similar car with verified headlight beams but again, that's not a guarantee that you'll be within spec and need an adjustment during the test. You also will honestly struggle very hard to do anything with the diagonal cutoff.
I don't work in a garage at the moment, however in my last workplace which charged for everything adjustment wasn't going to break the bank but it's also possible they won't charge much or anything at all for headlamp beam adjustment, which it sounds like you're liable to need given that someone was messing about with the beam adjusters for whatever reason and may have knocked one or other parts of the beam out. As for your removal and replacement of a headlight, this type is very well fitted to the car so I really think the headlight you removed should be as near as exactly the same as it was when it left SA, etc.
I really think you should just take it to the test station, maybe 20 mins earlier than you're booked in for, and mention it in an advanced call if they're a particularly busy test station; say that the headlights might be a bit out of alignment and determine then with them, which way to go forward. Adjustment's simply only a 2 minute job on a 6R/6C Polo when you've all the proper gear (it needs no special tools and has easy access to all adjusters) so I don't forsee any issues with passing because of them even if they are out a little. Unless of course you've put the headlights back in backwards or upside down which is ridiculous and impossible anyway!
If you really think they could be way out I also advise not driving in the dark until the test is due, but if you're near a garage with the gear, or a test station and have ten minutes to spare any time before your test, pop in and have it sorted there and then, m8.
Ring a few garages to see if they charge for it with the MOT perhaps?
I still think some won't even in London...
ed.silmon-monerri
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Re: How should I check the alignment of my headlights?

Post by ed.silmon-monerri »

This is the relevant part of the test manual. https://www.mot-testing.service.gov.uk/ ... ection_4.1

I think it will only prove to confuse you further as it has done to me. I also don't think it provides a suitable basis for figuring it out yourself, without the appropriate beam tester setup but you're welcome to prove me wrong.

The whole manual is available for free from that website. It's part of the government network, but it just has a its own domain name...
veteran
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Re: How should I check the alignment of my headlights?

Post by veteran »

I'm afraid to inform that I'm well ahead of you in this matter, as I downloaded and printed out the current requirements of the MOT (the so-called MOT Tester's Manual) from that website more than a week ago, so I already 'know the score', so to speak.

I think you're wrong to assume that a useful DIY check on headlight alignment on a modern car cannot be done. You must live in a totally different world to me too, as no MOT test station around here would possibly find the time - even a few minutes - to provide me with a pre-Test check-and-adjust, especially one that'd be free of charge; they're simply far too busy. All work at the stations around here is strictly by being pre-booked, usually at least a week before. As soon as one car comes off the ramps, MOT finished, the next one drives on to them. There are, of course, other garages and service stations where this sort of thing could nonetheless be done, but that would be missing the point entirely. The object of the exercise is to do the job myself and to learn something about the beam patterns of this Polo.
ed.silmon-monerri
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Re: How should I check the alignment of my headlights?

Post by ed.silmon-monerri »

I've spent some time in London though not having cars MOT'd so I'll have to take your word for it on that but I can well imagine! I had a look at the manual info a while ago, when there were issues with the lights on this car (which was crashed prior to my coming across it) as someone had seriously messed with the headlight main beam. I believe there's a third knob for that towards the centre of the car. And it's probably for good reasons that the headlamp adjustment isn't as well publicised as other critical yet often ignored yet remarkably simple, other parts of everyday vehicle maintenance. When I bought the Polo, someone before had managed to point one of the main beams upwards at nearly a 45 degree angle and at night one light just pointed at the trees making focusing on the road confusing and very tiring and frankly dangerous.
All that said, you never really know how appropriate the beams are for you unless you drive at night with them all in various situations and adjust it a little at a time/as necessary on the side of the road if that's what you want to do. The only one guaranteed potentially useful thing I can tell you about this car's headlights is that both the dipped beam and full beam come on together (whereas on other cars dipped beam is disabled with full beam on) and for me at least I think there's good coverage by both sets of lights. Dipped beam only has single filament H7's as I've just replaced one (after 4 years/30k miles).
One more thing that I may have already mentioned is that I don't think the full beam will be checked by the tester so while you likely won't need to worry about them for the test, you might need to take a few journeys and park near a suitable object etc. to line the full beam overlap to the dipped beam to exactly where you want it. I found it easy enough to tweak that against a garage door from around 15 feet away. YMMV. But I still think you'll struggle with the dipped beam cutoff setting especially as you had never heard of it until a couple of days ago. I can only assume mine is within spec or the tester adjusted it (or just passed it anyway?!) as nothing was mentioned at the time.
I trained in a main dealership 20 years ago, albeit Ford, and I like to think I know what I'm talking about including during my use of scepticism regarding other mechanics, however if you figure it all out and can describe it accurately in one or two short sentences please share it/them here lol as as yet I can't but I have other things to do and will spend time doing them in the meantime, instead. Things such as working out why there's an horrific rhythmic clunking sound coming from the gearbox on tickover. It's of little comfort to me to fairly confidently think that "it's probably just the dual mass flywheel" but for now the gearbox is staying on the engine...Regards...
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