Lighting is the most frustrating MOT category, because it's also the cheapest to avoid. A blown bulb costs pennies and takes minutes, but it still fails the test and still means a retest.
Lighting is the most frustrating MOT category, because it's also the cheapest to avoid. A blown bulb costs pennies and takes minutes, but it still fails the test and still means a retest.
The one that catches people out is headlamp aim. It's not something you can eyeball on the drive — it's measured against a beam pattern on a headlamp aligner, and a car that looks fine at night can still sit outside the limits.
Below are the lighting defects that come up most often, and which of them you can genuinely sort yourself before the retest.
Headlamp aim beam image projected incorrectly
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.
Full explanation of Headlamp aim beam image projected incorrectly
Offside or nearside lamp not working
A required lamp isn't lighting. Which classification it gets depends on which lamp it is and whether any of the pair still works — a single dead number plate bulb is treated differently from both brake lights being out.
Full explanation of Offside or nearside lamp not working
Registration plate lamp not working
The small lamp that illuminates the rear number plate isn't lighting. If a plate has two lamps and one is out, it's still recorded. It's one of the most common and cheapest MOT failures there is — and one almost nobody notices, because you can't see it from the driver's seat.
Full explanation of Registration plate lamp not working
Headlamp lens deteriorated or damaged so the light output is affected
The plastic lens has gone cloudy, yellowed or cracked to the point that it scatters the beam. Testers judge it on light output and beam pattern, not on looks, so a slightly dull lens usually passes while a heavily fogged one that softens the beam cut-off doesn't.
Full explanation of Headlamp lens deteriorated or damaged so the light output is affected
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