Common but often-overlooked faults could lead to an automatic failure, car experts have warned.
While most motorists are aware that major issues like faulty brakes or worn tyres can cause an MOT failure, experts at car repair finance specialists Bumper have revealed eight little-known reasons that could result in your vehicle being deemed unroadworthy.
A spokesperson for Bumper said: “It’s easy to assume that small details won’t matter in an MOT, but that’s exactly what catches drivers out. Things like a hanging air freshener or a dashboard warning light might not seem serious, but they can lead to an instant fail.”
Stupid poxy car failed its stupid poxy MOT! pic.twitter.com/WEF5yZF9dv
— jamie gill (@jamiegill1976) March 11, 2025
“We often speak to customers who are surprised by the reasons they’ve failed – especially when it’s something as simple as a dirty number plate or worn windscreen wipers. These issues are avoidable, but they’re flagged for a reason: they relate to visibility, safety, and control.”
Here are eight common and surprising reasons your car could fail its MOT:
1. Hanging air fresheners
Anything obstructing your view — including hanging air fresheners — is considered a safety issue.
“Obstructions from the rear-view mirror are a red flag in the test. It’s best to remove anything that might impair your line of sight,” the spokesperson added.
2. Dirty number plates
Plates must be clean and legible. Dirt or grime can obscure key information and trigger an instant failure.
3. Faulty horn
“Your horn must work properly – it’s not just for frustration, it’s there to warn other road users in emergencies. A faulty horn could compromise your ability to stay safe,” said the Bumper expert.
4. Worn driver’s seat
Loose or excessively worn seats can fail the test due to their impact on driver control.
5. Dashboard warning lights
Illuminated warning lights – such as those for the engine or airbag – are immediate fails unless properly diagnosed and resolved.
6. Poor windscreen wipers
Wipers must clear your windscreen effectively. Damaged or worn blades can hinder visibility.
“Replacing wipers is a low-cost fix that could save you from a failed test – and improve safety on the road,” the spokesperson noted.
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7. Incorrect headlight beam aim
Misaligned headlights can dazzle others or reduce your road visibility. Beam alignment is a common issue many drivers miss.
8. Damaged or missing mirrors
All mirrors – inside and out – must be secure and offer a full view of the road. Cracked or missing mirrors are classed as serious faults.
“Many drivers underestimate the importance of properly aligned mirrors and functioning lights. But your MOT is about making sure your vehicle is fully roadworthy — from top to bottom,” the expert added.
