Avoid NCT Test Failure

Common Reasons for NCT Test Failure and How to Avoid Them

The National Car Test (NCT) is a mandatory test that every car in Ireland must undergo to ensure it meets minimum safety standards. Many cars fail this test due to a variety of issues, some minor, others more significant. In this blog post, we’ll discuss the most common reasons for NCT test failure and provide tips on how you can identify these problems early and avoid failing your next NCT test.


Suspension failures, often caused by worn out bushes or leaking shock absorbers, are a common reason for NCT failure. A suspension imbalance, typically indicated by a more than 30% difference between the left and right, can affect your car’s braking and handling, which are safety-critical aspects. If your car makes clunking or creaking sounds as you drive, it may be time to get your suspension checked.

Tyre Condition

Tyres that are under-inflated, have less than 1.6mm of tread, show visible damage, or are not marked with the “E” mark can cause your car to fail the NCT test. Be sure to regularly check your tyre pressure (you can usually find the correct pressure inside your fuel filler cap) and ensure that your tyres are in good condition.

Headlamp Aim

Improper headlight alignment is another common reason for NCT failure. This usually occurs when replacement headlight bulbs have been fitted incorrectly. Although this is more of an adjustment issue than a replacement one, it’s probably best to have your headlight alignment checked by a professional. Some petrol stations have headlight alignment boards that can help you check your alignment.

Brake Lines/Hoses

Leaking brake hoses due to perishing and cracking over time can cause your car to fail the NCT test. It’s crucial to have these hoses replaced when they start leaking brake fluid, which can affect your braking system’s safety and functionality.

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Brake Performance

Brake performance issues, such as an imbalance in braking effectiveness between the left and right sides of the car, worn brake pads or discs, or a handbrake that needs adjusting, can also lead to an NCT failure. Regular checks and servicing can help identify these issues before they become problematic.


General lighting issues, including blown bulbs and cracked or faded lenses, are among the most common causes of NCT failure. Fortunately, replacing bulbs is typically a simple DIY job, and it’s worth regularly checking all your car’s lights to avoid any surprises during the NCT.

Brake Lights

Brake light function is crucial for safe driving and is a common area of failure during the NCT. A simple test to check your brake lights when you’re alone is to reverse up to a reflective surface, press the brakes, and check the reflection for three fully functioning brake lights in your rearview mirror.


Bodywork issues, including damaged or rusted components, cracked or broken lights, mirrors, and panels, can also cause your car to fail the NCT. Regular car maintenance and prompt repairs can help prevent these issues.


Steering system failures due to worn out bushes or ball joints, excessive play in the steering, or leaking power steering pumps, can result in an NCT fail. Regular check-ups can help identify and fix these issues before your NCT test.

Wipers / Visibility

Worn out or damaged wiper blades or a cracked or chipped windscreen can lead to instant NCT failure, especially if the crack orchip is within the driver’s line of sight. Regularly replacing your wiper blades and fixing any windscreen damage as soon as it happens can help you avoid failing your NCT on this count.

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How to Avoid NCT Test Failure

The key to avoiding NCT test failure is regular car maintenance. Regular checks of your tyres, brakes, lights, and windscreen can help identify potential issues before they become significant problems. If you notice anything unusual, like strange noises when you drive or a change in how your car handles, get it checked out by a professional as soon as possible. By taking good care of your car and addressing minor issues as they arise, you’ll have a better chance of passing your NCT test the first time around.


Sweeney’s Garage is here to help you with your car maintenance and ensure that you’re ready for your next NCT. Whether you need a regular service, a specific repair, or just some advice on maintaining your car, we’re here to help. Contact us today to book an appointment.