The beam pattern doesn't fall where it should when measured on a headlamp aligner. Too high dazzles oncoming traffic; too low means you can't see far enough ahead. Either way it's assessed against a fixed pattern, not by eye.
Wording as it commonly appears on an MOT certificate: “Headlamp aim beam image projected incorrectly”.
What does it mean?
The beam pattern doesn't fall where it should when measured on a headlamp aligner. Too high dazzles oncoming traffic; too low means you can't see far enough ahead. Either way it's assessed against a fixed pattern, not by eye.
How serious is it?
Usually recorded as: Major. The tester assesses the actual vehicle on the day, so your certificate is what counts.
What normally causes it?
- The manual levelling dial inside the car left on a load setting
- A new headlamp unit fitted and never set up
- Front-end knock, even a minor one, moving the unit
- Sagging or corroded headlamp adjusters on an older car
- Aftermarket LED bulbs in a reflector housing designed for halogen, which scatters the beam
What a mechanic would check
First thing is to check the levelling dial is on zero, because that catches out a surprising number of cars. Then it's on the beam setter and adjusted properly. If someone's fitted LED bulbs to a halogen reflector, no amount of adjusting will produce a correct pattern.
What might need replacing
- Adjustment only, in most cases
- A headlamp unit if the adjusters have broken
- Correct-spec bulbs refitted
Can you still drive it?
It's a failure. Adjustment is usually quick and cheap, and it's worth doing properly on a beam setter rather than against a garage wall.
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This is general guidance from a UK mechanic, not a substitute for a physical inspection. Only the tester who inspected your vehicle can confirm what was recorded and why.