MOT - Headlamp Alignment - Warning!

datostar

There's a recent thread on Honest John's website about an increasing number of cars failing the MOT on headlamp alignment (usually too low). Seems the MOT discounters are charging £11 or so to adjust them, but some are adjusting free of charge. This just happened to me with my Renault Megane. Fail certificate issued (no other faults), but Kwikfit adjusted them at no charge (don't mind mentioning the name as they do seem to get a lot of flak!) then immediately issued a pass certificate. There's a view that this another speed bump problem to be added to damaged tyres and springs. It's perfectly logical that the constant shocks applied to vehicles by them will cause this and that they will shake downwards rather than upwards due to gravity. Worth bearing in mind for those with an MOT due. I'll certainly check mine before the next one - it's never ever happened before.

KeithP

datostar wrote: »

There's a recent thread on Honest John's website about an increasing number of cars failing the MOT on headlamp alignment (usually too low). Seems the MOT discounters are charging £11 or so to adjust them, but some are adjusting free of charge. This just happened to me with my Renault Megane. Fail certificate issued (no other faults), but Kwikfit adjusted them at no charge (don't mind mentioning the name as they do seem to get a lot of flak!) then immediately issued a pass certificate. There's a view that this another speed bump problem to be added to damaged tyres and springs. It's perfectly logical that the constant shocks applied to vehicles by them will cause this and that they will shake downwards rather than upwards due to gravity. Worth bearing in mind for those with an MOT due. I'll certainly check mine before the next one - it's never ever happened before.

Re: bold bit...
But if the headlights are switched off while going over 'speed bumps', i.e. during daylight hours, the weight of the beam will be zero, will it not?
So gravity can have no affect on it.

Whether gravity tends to pull the front or the back of the headlight down, and thus the beam down or up respectively, depends on whether the headlight mounting points are towards the front or back of the unit.

hewhoisnotintheknow

what a lot of people forget is that you can use the button on the dash to (if you car has it ) to adjust the lights in many of these cases, hence it being free. if it needs changing under the bonnet its fair enough to charge

datostar

KeithP wrote: »

Re: bold bit...
But if the headlights are switched off while going over 'speed bumps', i.e. during daylight hours, the weight of the beam will be zero, will it not?
So gravity can have no affect on it.

Whether gravity tends to pull the front or the back of the headlight down, and thus the beam down or up respectively, depends on whether the headlight mounting points are towards the front or back of the unit.

Well certainly gravity will have no effect on a beam of light as it has no mass, but the direction of the beam is determined by the position of the internal reflector. The headlight mounting points are irrelevant as they are firmly fixed. Modern headlights have a moveable internal reflector and this is susceptible to vibration and shock.

datostar

hewhoisnotintheknow wrote: »

what a lot of people forget is that you can use the button on the dash to (if you car has it ) to adjust the lights in many of these cases, hence it being free. if it needs changing under the bonnet its fair enough to charge

Certainly, but in my particular case the dashboard adjuster was already at upward maximum so the reflectors had obviously moved downwards. Nothing wrong with charging for adjustment, but surely better to avoid the fail and consequent charges in the first place by checking them prior to MOT?

Inactive

datostar wrote: »

Nothing wrong with charging for adjustment, but surely better to avoid the fail and consequent charges in the first place by checking them prior to MOT?

How can anyone do that with any degree of accuracy?

Volcano

Inactive wrote: »

How can anyone do that with any degree of accuracy?

I think Haynes manuals still have the instructions to do this.

Can't reiterate enough that building a relationship with a good, local garage is worth it. Come MOT time, headlight alignment, bulb replacement, idle/mixture adjustment is done free for me and they'll even let a few minor fails go through as long as I promise to fix them later.

(No, I'm not a twenty-something female with a wardrobe of miniskirts either!)

Inactive

Volcano wrote: »

I think Haynes manuals still have the instructions to do this.

I wasn't thinking of the physical side of things, that is fairly straightforward for most people, I meant how to check the accuracy once you have adjusted them without a beam setter?

KeithP

datostar wrote: »

Well certainly gravity will have no effect on a beam of light as it has no mass, but the direction of the beam is determined by the position of the internal reflector. The headlight mounting points are irrelevant as they are firmly fixed. Modern headlights have a moveable internal reflector and this is susceptible to vibration and shock.

Thank you for the science lesson.
I, like most people, know that a light beam has no mass. Did you not see the smiley?

"The headlight mounting points are irrelevant as they are firmly fixed."
Did you see the word "tend" in my sentence?

"Modern headlights have a moveable internal reflector and this is susceptible to vibration and shock."
Oh, I didn't know we were talking about modern headlights.

Volcano

Inactive wrote: »

I wasn't thinking of the physical side of things, that is fairly straightforward for most people, I meant how to check the accuracy once you have adjusted them without a beam setter?

Hmm...Haynes manuals used to have a diagram you could draw on a wall, complete with measurements so you can adjust the beam accurately. Seems like the newer ones just suggest you get it done at a garage. Another nail in the coffin of home maintenance.....

LessThanSte

Volcano wrote: »

I think Haynes manuals still have the instructions to do this.

Can't reiterate enough that building a relationship with a good, local garage is worth it. Come MOT time, headlight alignment, bulb replacement, idle/mixture adjustment is done free for me and they'll even let a few minor fails go through as long as I promise to fix them later.

(No, I'm not a twenty-something female with a wardrobe of miniskirts either!)

Forget garages, the best option for MOT, hands down, are the council run MOT centres, who charge whatever the official rate is (i think £26 at the moment) and have absolutely no reason to rip you off (they dont do repairs, unless you ask them very very very nicely or happen to be driving around in a bin lorry).

That said, the first two times i went to the one in Walsall, the car failed on headlight adjustment which, with the aid of a screwdriver was fixed while i waited at no cost to me. He didnt even bother asking

Generally they dont seem to advertise that they do MOT's, its mostly for taxi's but the majority of them will do it if you ask. I think your meant to live within the council boundries but we live just outside and have never been questioned!