MOT defect file
Headlamp aim incorrect
Last updated
Quick answer
The beam pattern is outside the permitted range, which can dazzle other drivers. Usually a quick adjustment.
- Typical cost
- £20–£60
- DIY viability
- Possible with care
What you might notice
- Oncoming drivers flashing you when you are certain you are on dipped beam
- A beam that seems to fall short, lighting only a few car lengths of road ahead
- An obvious step or tilt in the cut-off line when you park facing a wall or a garage door
- Usually nothing — aim drifts slowly and your eyes adjust with it, which is why it is so often first found at the test
What causes it
- A knock to the front of the car, or a headlamp removed and refitted during bodywork
- A seized, cracked or stripped plastic adjuster inside the lamp — a known weak point that becomes brittle with age
- A permanently loaded boot or a heavy towbar nose weight pitching the car nose-up
- A failed levelling motor or ride-height sensor on cars with self-levelling xenon or LED lamps
Advisory or failure?
Headlamp aim has no advisory grading of its own — the beam image either falls inside the permitted box on the aim tester or it does not, and if it does not the result is a major defect. Testing is on dipped beam, and the two usual failures are a beam kicking up above the horizontal, which is what dazzles oncoming traffic, and one aimed so low that it fails the minimum drop. Aim pushed to the right, into the path of oncoming drivers, fails; a small amount of leftward bias is within tolerance. It is equally a major defect if the aim cannot be set because the adjuster is seized or broken, or if a levelling device fitted to the car does not work.
Can you fix it yourself?
Possible with care
You can get close at home — park square to a wall about 10 metres away on level ground, mark the centre of each beam and work the adjuster screws — but close is not what the tester measures. A garage uses a calibrated beam-setter and most will do it for the price of half an hour. Before touching an adjuster, rule out the cheap causes: tyre pressures, an unusually loaded boot, and an in-car levelling switch left on a setting for a full car.
What it costs
Adjustment alone is £20 to £40 at most garages, and is often folded into a free retest if the same garage did the original test. You reach the top of the band where the lamp has to come out to reach the adjuster. If the adjuster itself has snapped the cost leaves this band entirely, since the fix is a new headlamp unit — from around £80 for an aftermarket halogen lamp to several hundred pounds for an original-equipment LED assembly.
What happens if you ignore it
Lamps set high dazzle everyone coming the other way, which is antisocial and grounds for a police stop, while lamps set low leave you far less warning of what is on the road. Neither costs much to put right, which makes this the cheapest item on most retest lists — and therefore a poor one to leave until next year.
This is general guidance, not a diagnosis. The severity DVSA records depends on the specific fault found, so the same item can appear as an advisory on one test and a failure on another. Ask a qualified tester or mechanic to inspect the vehicle.
Has this been recorded on your car?
Check the full MOT history for any UK registration.