How to adjust headlights: Instruction (user:rde-groups CONTAINSANY 'XVIP_AMC_UK' AND user:rde-groups CONTAINSANY 'XHTW_Wholesaler')
How to adjust headlights: Instruction
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How to adjust headlights

Here you will find useful tips on the subject of adjusting headlight systems in vehicles.


We demonstrate how to professionally adjust vehicle headlights. The illustrated step-by-step instructions here give you quick and valuable assistance with e.g. measuring methods, vehicle inspection, positioning the headlight aiming device and checking and adjusting the headlights using a 10 meter wall. In a short video clip we also show you how to use a headlight aiming device (SEG V) to adjust a headlight.


Important note:
The following technical information and practical tips were created by HELLA to support professional automotive garages in their daily work. The information presented here on this website should only be used by trained automotive technicians taking the respective safety regulations and country-specific legislation and practice into account.


Overview: Headlight system aiming

Since asymmetric light distribution appeared on the market in 1957, there have also been statutory provisions for aiming headlights.

Headlights were first aimed at the so-called "10-metre wall". That means a vehicle is driven to a distance of 10 m in front of a lightcoloured wall, which has certain markings on it. The headlights are then checked or adjusted on the basis of these markings.

This has remained the statutory test method until today and is still used particularly for checking agricultural or specialist vehicles. One of the disadvantages of this method is that you need a relatively, large, light-coloured and free wall, and a corresponding amount of space to go with it. Neither of these were, or are, exactly easy to find in a garage.

These circumstances were also ultimately among the factors responsible for the development of beam setters. Such devices enable the light distribution to be checked quicker and more flexibly.

The following pages describe the measuring methods, the legal basis and the most important stages involved in headlamp aiming.

Professional headlight adjustment: Clip


Professional headlight adjustment using HELLA GUTMANN SOLUTIONS

Adjusting a headlight with the beamsetter (SEG V)

04:39 min


Headlight adjustment tool: Optimal setting of the device


Measuring method

Beam setters generally simulate the 10 m wall. The lens installed in the beam setter box shortens the prescribed 10 m distance to 50 cm (Fig. 2 - lens to test screen)

The disadvantages, such as storage space and a suitable wall, are omitted. A beam setter can also be flexibly used at different places within the garage, provided the garage floor adheres to the required tolerances.

Headlight aiming site

The composition and condition of the floor are of primary importance to enable exact headlight aiming. That is why, it also has its own standard (DIN ISO 10604) in which the "test surface" is specified precisely and the permissible tolerances listed. The graphics listed in diagram 3 clearly illustrate the requirements.

Sample calculation

If these tolerances are not adhered to, even minor deviations have a large impact on light distribution.

A sample calculation makes it clear:

As already mentioned, a lens is installed in the beam setter which shortens the prescribed 10 m measuring distance to the wall to only 50 cm. A mere 5 mm error in the measurment on the test screen of the beam setter thus corresponds to 10 cm difference over 10 m (ratio 10 m to 50 cm is factor 20). A vehicle with headlights installed at a height of 60 cm has a dipped headlight with a range of 60 metres (at 1% forward tilt = 10 cm inclination to 10 m range).

This means the light projected by the headlight would deviate by 60 cm! This example clearly illustrates the decisive effect that a precise test surface has on light distribution, as the difference between glare or driving in semi-darkness is measured in millimetres!

Vehicle test

Not only the floor conditions are important. The vehicle must also have been prepared for the test.

The following points must be observed:

  • Test the headlight function.
  • Check the cover lenses for damage from stones, scratches and for dullness.
  • The tyres must have the prescribed air pressure.
  • Check the vehicle with a person on the driver's seat or a weight of 75 kg, which is otherwise not loaded.
  • No load is required for trucks and other multi-lane vehicles.
  • Single-lane vehicles and single-axle traction or working machines (with seat cart or trailer) should be checked with a person on the driver's seat or a 75 kg load.
  • In the case of vehicles with hydraulic or air suspension, manufacturers' instructions must be heeded.
  • If automatic correction of the headlights or an infinite or multi-stage setting fixture is available, follow the manufacturer's instructions. In this case, various function tests, depending on the manufacturer, must be carried out.
  • A diagnosis tester is required for adjusting various vehicles with automatic headlight range adjustment, since the control unit has to be in “basic mode” during adjustment. If the cut-off line is set correctly, this value is set as the new control value, Fig. 4.

Setting up the beam setter

If the floor conditions are acceptable and the vehicle has been checked, the beam setter still has to be aligned to enable exact adjustment.

The beam setter is moved in front of the headlight to be checked. The beam setter box must be aligned to the middle of the headlight or to the light source. Vertical and horizontal deviations may not exceed 3 cm. The distance between the beam setter box and the headlight varies depending on the manufacturer. In the case of HELLA devices, the distance from the front edge of the beam setter box to the headlight should be between 30 and 70 cm, Fig. 5.

The beam setter box is then aligned to the vehicle. Devices with a wheel-mounted base must be individually aligned for each headlight to be checked. Beam setter devices on rails only need to be aligned once. Using the broad-band, laser or mirror sight, align the beam setter box in such a way that the sight line touches two points situated at the same height, symmetrically to the vehicle’s longitudinal axis, Fig. 5, dashed lines.

Set the forward inclination of the cut-off line

Finally, set the "forward inclination" on the device. This corresponds to the angle of inclination of the headlight cut-off line. The forward inclination is given in % and can normally be found on the headlight, Fig. 6.

For example, 1% means that the dipped headlight is at an angle of 10 cm at a range of 10 m. The test screen is set to the correct percentage using the scaled wheel, Fig. 7.

Adjustment table

Below you will find two tables containing the main setting dimensions for different vehicle types.

How to check headlight alignment: Setting the light distribution

 The device now has an optimal setting and the different light distributions can be set.


Headlights with asymmetrically dipped headlight

Align device according to point 4.0. Set the scaled wheel according to the adjustment table (observe point 4).

Turn on the dipped headlight:
In the case of headlights with asymmetrically dipped headlights, the cut-off line must touch the dividing line on the test surface. The bend point between the left and right sloping part of the cut-off line must run vertically through the central marking (upper cross). The bright core of the light beam must be situated to the right of the vertical line running through the central marking. For easier determination of the left headlight half of the bend point (viewed from a driving direction), cover and then uncover again several times. Then recheck the dipped headlight.

Main beam: In accordance with the prescribed setting of the dipped headlight's cut-off line, the middle of the light beam must lie on the centre marking (upper cross).


Fog light

Align the device according to point 4.0.

Set the scaled wheel according to the adjustment table (observe point 4).

Turn on the fog light:
The cut-off line must run as horizontally as possible along the dividing line over the whole width of the screen. Correct the headlight aiming if necessary using the adjustment options.

Special headlights for high beam (e.g. auxiliary driving lights)

Align the device according to point 4.0.

Set the scaled wheel according to the adjustment table.

Turn on the main beam:
The light beam centre of the main beam must be on the central marking, correct if necessary using the adjustment option.

In the case of separate main beam modules (e.g. in combination with Bi-Xenon headlights), the main beam should be aimed according to manufacturers' instructions, since different settings are possible in this case.

Adjusting the "glare-free high beam cutoff line"

Some manufacturers have also been offering so-called "main beam assistants" for some time now as an optional feature. A camera installed in the windscreen recognises when a vehicle is approaching or driving in front of your car and automatically switches the main beam to low. In addition, there is also the so-called "glare-free high beam cut-off line". This high beam system produces a very special light distribution on the road.

In contrast to a normal high beam that is displayed on the test screen as an oval spot of light, the shape of the glare-free high beam cut-off line tends to be square, Fig. 9.

In order to adjust the main beam function, a menu needs to be called up using a diagnosis tester. The headlights are moved into a certain position and the glare-free high beam cut-off line is activated. Now the vertical line of the light distribution (red circle) must be adjusted exactly to the central marking of the test screen. In the case of the glare-free high beam cut-off line, correct adjustment is absolutely essential as otherwise other road users may be exposed to extreme glare.

Photoelectric light measuring device (Incident Light Meter)

After adjusting the headlights, the incident light meter can be used to check whether the highest permissible glare value of the dipped headlight has been exceeded. Today's beam setters are generally equipped with a digital incident light meter, Fig. 10.

If the glare has been clearly exceeded, the headlight must be replaced so as not to blind other road users.

Aligning the beam setter to the vehicle's longitudinal axis

As already mentioned, the condition of the floor is of primary importance to enable exact headlight aiming. That is also the reason for the low tolerance values. But what should be done if the aiming device and the vehicle are standing on surfaces which are not on the same level?

 An example to make this clear.
In many garages, the first two metres, measured from the outside wall to the middle of the interior, form a horizontal surface. After that, there is a second, slightly sloped area which extends to the water drain channel in the middle of the garage. This area is where the lifting ramp or work-position is situated. If, therefore, a vehicle is driven on to the work-position and the headlight aiming device is situated on the afore-mentioned horizontal surface, the longitudinal axes of the aiming device and the vehicle are not parallel to each other. That inevitably leads to wrong measurements.

On the following pages, we will show you two ways of solving this problem step by step. However, this requires an aiming device on which the inclination of the longitudinal axis of the beam setter box can be adjusted, e.g. by an eccentric axis, Fig. 11

Headlight aiming: Test spectrum



Aiming with a 10-metre wall

As already mentioned, this method is still mainly used today for vehicles where the upper edge of the headlights is higher than 140 cm above the ground. The vehicle is driven on to a level surface, which does not have to be horizontal, to a distance of 10 metres from a vertical, light-coloured wall

The following lines have to be marked on the wall.

Line A
Extend the longitudinal axis of the vehicle to the test wall and mark it with a vertical line.

Line B and C
Measure the distance X of the vehicle headlight (centre to centre) and mark it on the wall symmetrically to Line A.

Line D
Draw this line at a distance ‘e’ below Line H.
Line H
Measure the height of the centre of the headlights above the ground draw the line on the test wall parallel to the ground.

Adjusting the headlights
Cover the right headlight and align the left headlight so that the horizontal part of the cutoff line touches Line D. Then align the headlight laterally. The bend between the horizontal and the sloping (asymmetrical) part of the cut-off line must lie on Line B. Then align the right headlight in the same way. In this case, the bend of the cut-off line lies on Line C.