April 25, 2007 at 4:55 pm

THE MoT TEST – Lighting

The lighting section of the MoT covers all exterior lamps required by the Road Traffic Act; this excludes front fog lamps, reversing lights and work lights as fitted to some commercial vehicles.

By and large all required lights must switch on and off when required, be correctly positioned, give out light of the correct colour and not affect or be affected by the operation of any other light.

Firstly lets take a look at the sidelights, or more correctly, the position lights, these not only indicate the vehicles presence but also its approximate width, so a couple of white LEDs mounted in the grille is easily going to get you an MoT failure. Much the same applies to the rear position lights and in common with all other required lights must not flicker or go off when tapped lightly.  Quite common within the motoring community at the younger end of the population is the fitting of blue sidelights especially at the front, again a guaranteed MoT fail as the regulations require they must show a steady white light to the front, or a yellow light, if incorporated in a headlamp which emits a yellow lightâ€?

One particular chaffing point between vehicle owners and MoT testers is the subject of damage, I personally have seen countless lamp units of all types with holes, cracks, incomplete lenses attended by an indignant owner clutching a freshly issued fail sheet insisting that I should have used some discretion when assessing that particular lamp, the regulations however, are quite clear, and state:

A front or rear position lamp incomplete, not in good working order or not clean, i.e. damaged or deteriorated, or not visible from a reasonable distance.

If damaged, the replacement of most lamp units can be fairly easy and other than the main dealers, many suppliers can offer replacement at a competitive price and should there not be a ready source the required unit from one of the second-hand parts companies will fill the void. One recommended source for used car parts are breakers yards where you can get a fully functioning Vauxhall headlamp N/S and/or O/S for almost nothing.

The next lamps that work in conjunction with the side/position lamps are the registration plate lights. The requirements for these are straight forward and must be:

  • Fitted
  • Secure
  • Working
  • Correctly positioned
  • Not flicker when tapped
  • Not show a white light to the rear

One of the biggest problems with these lights is that of bulb holder corrosion which in turn can affect the wiring. Keeping the holder free from moisture is the basis of fault prevention and there are numerous aerosol sprays which do a fine job in keeping the bulb contacts rot free.

Whilst at the rear of the vehicle the MoT tester needs to check the rear fog light, which has been a required fitment to the offside or centre of vehicles since April 1980. This lamp must not be;

  • Missing
  • Emitting any colour other than red
  • Incomplete
  • Not in good working order
  • Insecure, obscured or not facing rearward
  • Flickers when tapped by hand
  • Affected by the operation of other lamp
  • Tell-tail (warning lamp) does not work

As with all other required lights, the switch must also meet certain specifications in that it must be present, in good working order and secure.

Another rear mounted lamp which is included in the MoT is of course the brake or stop lamps and they must obviously be fitted for the inspection to proceed. Since January 1971 a vehicle must be fitted with two stop lights and they must emit a steady red light when the service brakes are operated, go off, be complete, clean, in good working order, secure and face rearward. One minor quirk of the regulations is that additional stop lamps are not a testable item IF there is doubt as to whether they are connected.

Also tested whilst at the rear of the vehicle are the indicators which of course are fitted to all four corners and since April 1986 must include side repeaters. In common with all other required lamps they must be in good working condition, present, secure, showing light of the appropriate colour (amber) or affected by the operation of another lamp. Different to any other lamp of course is that they must flash at a rate of between one and two times per second (60-120 times per minute).

Closely related to the indicators are the hazard warning lights which have been a required fitment since April 1986. By the operation of a single switch all indicators must flash in phase with both the ignition on and off. In common with the indicators is the requirement for a “tell tale� to warn the driver that the hazard lights are on.

Last but certainly not least are the headlamps which have the same basic requirements as the other lights, security, condition etc but also have a requirement regarding aim. Basically, this is checked with the headlamp aligner which when correctly positioned in front of each headlamp in turn will, with the lamp on, display the projected beam image which has the following requirements: flat horizontal illumination just below the straight ahead a kick up image rising above the horizontal and away to the left, the point at which the image kicks up must be just to the left of the vertical centre line. Any deviation from the above will result in a fail unless it can be corrected via the “height adjuster control by the driver or by simple adjustment which is now permitted to be carried out during the test. The other variation from the norm is that headlamps are permitted to show either a yellow or substantially white light, anything else will fail.

I am sure that it will come as no surprise that the most common reason for MoT failure in automotive lighting is blown bulbs, a quick replacement and that’s that. Another very common area is that of headlamp aim and in many cases a tweak with a screwdriver will suffice and if at all possible this should be done by the MoT station as they will have access to the correct alignment equipment.