How does a headlight tester work?

By Pavan Jheeta
Headlamp tester in action

Headlight alignment is one of the easiest things to overlook in the everyday maintenance of a fleet.

But it’s also one of the most common causes of failure at an MOT — which means you can’t afford to ignore it.

The best place to start is with a proper understanding of what’s involved: the tech and tools you need to test it, and what to look for in the results.

Here’s what you need to know:

 

What’s the basic idea?

A headlight tester (also known as a headlight beam setter) uses a lens to focus the light from a vehicle’s headlamps.

The focused light is then projected onto a screen at the back of the unit, which has printed lines and measurements on it.

By comparing the pattern of light on the screen to the printed lines and measurements, you’ll be able to see exactly how the beams from your vehicle headlights are performing.

 

What does it test for?

A headlight tester is used to look at two types of measurement:

  1. The intensity of the beam.
  2. The orientation of the beam.

For the intensity of the beam, a headlamp tester uses a light meter (also known as a Lux meter — where ‘luxes’ are a unit of illuminance).

For the orientation of the beam, things get a little more complex. A headlight tester will be looking for:

  • The ‘kick-up’ — a bias pointing to the verge of the road (to the left in the UK)
  • The ‘break point’ — where the kick-up meets the flat part of the beam
  • The ‘horizontal cut off’ — the edge of the beam on the road straight ahead

 

How do you use a headlight tester?

Not every headlight tester is the same. But in most cases, they all follow the same general principles:

  1. Use a flat, even surface for both the vehicle and the headlight tester.
  2. Line up the tester so it’s pointing along the length of the vehicle.
  3. Adjust the height of the tester so it’s aligned with the centre of the headlight (some units include laser alignment to help with this — like our 2600 Headlamp Tester).
  4. Turn the vehicle headlights on at the setting you’re testing.
  5. Inspect the light that’s projected on the screen, and compare it to the printed guidelines.

 

What do the results mean?

Where the projected image falls outside of the printed guidelines, it means your headlights are out of alignment — and you’ll need to adjust them on the vehicle to bring them into an acceptable range.

And if you’re testing in-house with your own headlamp tester?

Congratulations — you’ve just saved yourself from a failed MOT!

Faulty headlights are one of the most common reasons for failure at your annual tests. But with your own DVSA-approved equipment on hand, you can make sure every vehicle in your fleet is ready for its tests — without waiting to find out on the day.

So if you’re running a fleet and you’re preparing for MOTs, an investment in your own headlight testers could easily pay for itself in the long run.

Take a look at our full range of Totalkare Headlamp Testers — or start a chat with one of our workshop experts to find out what you need.