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How those pesky dashboard warning lights can affect your car's NCT

We’re here to help you decode them.
Feb 26th 2018, 5:12 PM 17,991 1

DASH WARNING LIGHTS are built into the instrument binnacle of a car. Modern motors are fitted with a number of warning lamps on the dashboard that let the driver know if certain critical safety, performance and environmental features are not working properly.

Some of the lights are easy to understand and fix, like adding screen wash to the reservoir and checking the tyre pressure, but some are a little more difficult to interpret.

One thing that does help with understanding the problem is the colour of the light.

The warning lights are colour coded to help convey the severity of the issue. The lights glow green, orange and red.

Green lights aren’t really a warning, they just indicate that something is on, for example the car’s lights.

Orange lights indicate that something is wrong and needs your attention but the issue isn’t safety critical. For example tyre pressure indicators on more modern cars.

Red lights indicate an issue that is serious and demands immediate attention. This could be something like the low engine oil light or coolant warning light.

Ignoring the lights, especially red ones, can cause damage to the car – but did you know the lights can also affect the outcome of your car’s NCT?

The dash warning lights that affect NCT results:

Engine warning light: If this light remains on, then the smoke test on diesel-engined vehicles cannot be carried out until the issue is rectified.

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Engine oil pressure light: Similarly, the smoke test on diesel-engined vehicles cannot be carried out until the issue is rectified.

Oil warning light: When this light remains on with the engine running the Exhaust CO/HC/LAMBDA test cannot be carried out.

Main beam warning light: If this isn’t working properly, your car will fail the ‘headlamp condition’ part of the NCT.

The NCT also checks that the Malfunction Indicators are in working order. You car will fail this part of the NCT if the following dash lights are not working or if an obvious modification affects correct operation:

  • Supplemental Restraint Systems
  • Airbags
  • Electronic Stability Control
  • Anti-Lock Braking System
  • Electronic Braking System
  • Parking Brake
  • Tyre Pressure Monitoring System
  • Electronic Power Steering
  • Brake fluid warning light

If a light comes on when you are driving, don’t panic. Just pull over somewhere safe and convenient and find the manual to work out what the light means, what needs attention and how urgently the issue needs to be addressed. And of course, get them sorted out before the NCT.

READ: 5 of my favourite performance arms of car manufacturers >

READ: What are those numbers by the side of the motorway and what are they for? >

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Melanie May


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