Common reasons for an MOT failure and what to do if your car fails

The MOT test is a legal requirement for most vehicles over three years old in the UK. It checks that a vehicle meets minimum road safety and environmental standards.

Many MOT failures are caused by faults that drivers can identify and fix before the test. A few simple checks could save the inconvenience of a failed MOT and the cost of a retest.

What are the most common reasons for an MOT failure?

Many MOT failures are caused by basic maintenance issues rather than major mechanical faults. .

1. Lights and electrical faults

Faulty lights are among the most common reasons for MOT failures.

The MOT inspection includes checks on:

• Headlights
• Brake lights
• Indicators
• Number plate lights
• Rear lights

A blown bulb, faulty connection or damaged lens can result in a failure.

Before the test, switch on all lights and check that they are working correctly.

2. Windscreen wipers and washers

The tester must be satisfied that the driver can see clearly through the windscreen.

Common failures include:

• Damaged or split wiper blades
• Washer jets that do not operate correctly
• Empty washer fluid reservoirs

If your wipers smear the screen or leave large areas uncleared, replace them before the test.

3. Tyre condition and tread depth

Tyres are a key safety item and are examined carefully during an MOT.

Check for:

• Low tread depth
• Cuts and cracks
• Bulges
• Exposed cords
• Uneven wear

The legal minimum tread depth for cars in the UK is 1.6mm across the central three-quarters of the tyre and around the entire circumference.

Tyres that do not meet legal requirements will fail the MOT.

4. Visibility issues

The driver must have a clear view of the road.

A vehicle may fail if:

• Damage to the windscreen falls within a critical area
• Objects obstruct the driver's view
• Visibility is impaired by damage or defects

As a guide, a chip larger than 10mm in the driver's field of vision can result in a failure. Elsewhere in the swept area of the windscreen, damage over 40mm may lead to an MOT failure.

5. Dashboard warning lights

Modern vehicles use warning lights to alert drivers to faults.

Certain warning lights associated with testable systems can result in an MOT failure if they remain illuminated.

Tony Rich, road safety spokesperson at The AA, says: "Engine management, ABS, tyre pressure monitoring and stability lights should go out within two seconds, apart from the handbrake light."

If a warning light remains on, the fault should be investigated before the MOT test.

What do I do if my MOT fails?

If your vehicle fails its MOT, you can leave it at the test centre for essential repairs. As long as the repairs are done within 10 working days of the test, your vehicle can then be retested for free.

If you want your car to be repaired elsewhere, you can still get it retested for free at the original test centre, as long as you return it before the end of the next working day.

You can only take your car elsewhere if the current MOT certificate is still valid and the MOT test didn't report a dangerous defect.

MOT failures are categorised according to the seriousness of the defect.

Dangerous defects

Dangerous defects indicate an immediate risk to road safety or the environment.

A vehicle with a dangerous defect fails the MOT and should not be driven until repaired.

Lee Morley says: "We strongly advice against driving a vehicle with a known dangerous defect. By doing so, you are potentially putting yourself and others at unnecessary risk."

Major defects

Major defects result in an MOT failure but are considered less severe than dangerous defects.

Examples can include faults affecting:

• Suspension
• Lighting
• Tyres
• Steering components

If the vehicle still has a valid MOT certificate, there may be circumstances in which it can be driven. However, it must remain roadworthy.

Advisories

Advisories highlight items that are worn or deteriorating but do not currently meet the threshold for failure.

Lee Morley explains: "An advisory item highlights a potential issue identified during the MOT test. While it may not be dangerous at the time of inspection, it could deteriorate and become a safety risk if left unchecked. That's why we recommend addressing advisory items as soon as possible."

Advisories should not be ignored, as they often indicate repairs that will be needed in the near future.

MOT retests: what are the rules?

Retest arrangements depend on:

• The reason for failure
• Where repairs are carried out
• How quickly the vehicle is returned for inspection

In some circumstances, a free partial retest may be available if repairs are completed promptly and the vehicle is returned to the same test station.

If repairs take longer or the vehicle is tested elsewhere, additional fees may apply.

The garage carrying out the MOT will be able to explain the retest options available in your situation.

Can I appeal if my vehicle fails the MOT?

If you think the MOT result is wrong, ask the test centre why your vehicle has failed. If you still believe the reasons are incorrect you can appeal.

You'll need to complete a complaint form and send it to the Driver and Vehicle Standards Agency (DVSA) within 14 working days of the test.

The DVSA will contact you within 5 working days if they decide your vehicle needs a retest. You'll need to pay for a full test, and if the vehicle does pass you'll get a part or full refund of the fee.

Quick checks to carry out before your MOT to reduce the risk of failure

A few simple checks can help reduce the risk of an unexpected failure.

Lee Morley, AA expert patrol, recommends checking: "Carrying out simple checks on the operation and condition of your lights, wipers and tyres can save you the cost and inconvenience of an MOT retest."

1. Check fluid levels

Make sure there is sufficient windscreen washer fluid in the reservoir.

The washer system must be capable of cleaning the windscreen effectively during the MOT inspection.

Inspect your wiper blades.

Replace wiper blades if they:

• Smear the screen
• Leave streaks
• Show signs of splitting or damage

Replacement blades are usually inexpensive and easy to fit.

2. Check all exterior lights

Inspect:

• Headlights
• Brake lights
• Indicators
• Side lights
• Rear lights

If possible, ask someone to help check the lights or use reflections from a wall or window.

Some modern vehicles require specialist access to replace bulbs, so professional assistance may be needed.

3. Check your number plates

Ensure number plates are:

• Securely attached
• Clean
• Easy to read
• Not damaged

A damaged or illegible number plate can lead to an MOT failure.

Booking an MOT test with The AA

When you book an MOT you get:

• Testing at AA approved garages.
• Quick and easy online booking and payment.
• Repair parts and labour are guaranteed for 1 year or up to 12,000 miles.
• Fair, transparent pricing.

And if you book a service with an MOT, you can get free vehicle collection and return, subject to availability.

If your car does fail its MOT and you'd like us to make the necessary repairs, we can carry out your retest for free.