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Top 10 Reasons Cars Fail the NCT in Ireland

Based on RSA data and common issues found during National Car Testing. Click each item to learn more about prevention and what to check before buying a used car.

1
Lighting & Electrical Issues
▼

32% of NCT failures - The most common reason for failing the NCT. This includes faulty headlights, indicators, brake lights, fog lights, and number plate lighting.

💡 Prevention Tips:
  • Check all lights weekly - walk around your car
  • Replace bulbs in pairs for consistent brightness
  • Clean light lenses regularly
  • Ensure headlight alignment is correct
  • Check that all electrical connections are secure
2
Suspension & Steering
▼

28% of NCT failures - Worn shock absorbers, damaged springs, loose ball joints, and steering play issues.

🔧 Prevention Tips:
  • Listen for unusual noises when turning or going over bumps
  • Check for excessive bouncing after hitting a bump
  • Inspect tyres for uneven wear patterns
  • Have alignment checked annually
  • Don't ignore steering wheel vibration
3
Tyres & Wheels
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25% of NCT failures - Illegal tread depth (below 1.6mm), sidewall damage, mismatched tyres, or incorrect tyre pressures.

🛞 Prevention Tips:
  • Check tread depth monthly with a 20c coin
  • Maintain correct tyre pressures (check monthly)
  • Inspect for cuts, bulges, or embedded objects
  • Rotate tyres every 10,000km for even wear
  • Replace tyres in pairs on the same axle
4
Brake System
▼

22% of NCT failures - Worn brake pads, damaged discs, brake fluid leaks, or incorrect brake balance.

🛑 Prevention Tips:
  • Listen for squealing or grinding noises
  • Check brake fluid level monthly
  • Feel for pulsing or vibration when braking
  • Have brake pads checked every service
  • Don't ignore the brake warning light
5
Emissions & Exhaust
▼

18% of NCT failures - Excessive emissions, damaged catalytic converter, exhaust leaks, or faulty emissions control systems.

💨 Prevention Tips:
  • Take your car on regular long drives
  • Use quality fuel and occasional system cleaners
  • Address check engine lights immediately
  • Have emissions tested before NCT if concerned
  • Keep exhaust system free from damage
6
Windscreen & Mirrors
▼

15% of NCT failures - Cracked windscreen, damaged mirrors, non-functioning wipers, or obstructed view.

🪟 Prevention Tips:
  • Repair windscreen chips immediately
  • Replace wiper blades annually
  • Keep windscreen washer fluid topped up
  • Ensure all mirrors are secure and uncracked
  • Remove any obstructions from windows
7
Body & Chassis
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12% of NCT failures - Structural corrosion, damaged seatbelts, loose panels, or safety-related bodywork issues.

🔩 Prevention Tips:
  • Wash your car regularly, including the underside
  • Check seatbelts for fraying or damage
  • Address rust spots before they spread
  • Ensure all panels are secure
  • Keep drainage holes clear
8
Engine & Drivetrain
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10% of NCT failures - Engine mounts, transmission leaks, clutch issues, or drivetrain problems.

⚙️ Prevention Tips:
  • Regular oil changes and servicing
  • Check for fluid leaks under the car
  • Address unusual noises or vibrations
  • Don't ignore clutch slip or gear issues
  • Warm up the engine before the NCT
9
Horn & Communication
▼

8% of NCT failures - Non-functioning horn, damaged registration plates, or missing/illegible VIN numbers.

📯 Prevention Tips:
  • Test your horn regularly
  • Keep number plates clean and secure
  • Ensure VIN is visible and readable
  • Replace damaged number plate lights
  • Check horn button works properly
10
Fuel System & Tank
▼

5% of NCT failures - Fuel leaks, damaged fuel lines, loose fuel cap, or contaminated fuel system.

⛽ Prevention Tips:
  • Check for fuel smells or stains
  • Ensure fuel cap seals properly
  • Use quality fuel from reputable stations
  • Address check engine lights promptly
  • Keep fuel system clean with occasional treatments

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