How to Checking headlamps and lights

Checking headlamps and lights

Here you can get How to Checking headlamps and lights.

It is an offense in law to not have all obligatory lights working. Check them frequently, especially before an evening journey. Walk round the car while someone works the switches.

Obligatory lights are side and tail lights, headlamps (main and dipped beams), direction indicators, stop lights and a rear number-plate light. When fitted, reversing lights, fog lights (front and rear), long-range driving lights and hazard warning lights should even be working. Wipe all the lenses with a clean cloth, checking them for damage. If a lens is cracked, seal it temporarily with clear tape , taking care to not obscure more of the glass than absolutely necessary.

Damaged lenses must be replaced as soon as possible, both for safety and to prevent moisture entering the lamp fixture. Water will tarnish the reflector, and corroded connections will soon put the lamp out of action.

Checking headlamps

On many modern cars the headlamp bulb can be reached from inside the bonnet; on others it’s necessary to remove the lamp bezel or grille on the front of the car. Failure of one headlamp is usually confined to either the most beam or the dipped beam. In a lamp unit fitted with a bulb, this is often easy to check: remove the bulb, hold it up to the light and see if any filaments are broken.

If the bulb is of the halogen type, it should not be touched with the fingers. Use a clean, dust-free cloth to stay fingermarks off it and avoid premature failure. Clean it with mentholated spirit on a cloth if necessary. Filament damage can’t be seen during a sealed-beam unit, and a special method is required to see if it’s faulty (see panel on right). Checks on wiring and connections must include the spring-loaded contacts, where that sort of bayonet bulb holder has been used.

A sticking plunger could end in the failure of the lights therein unit, while failure of an insulating washer could mean a brief circuit and a dimming of all the lights, or cause a fuse to blow. A dim traffic light on one side is typically a faulty earth connection between the headlamp and therefore the body of the car. The connection is usually simply a wire lead attached to the body; corrosion or dirt may cause a high resistance within the connection which results in a dim light.

Unbolt the connection, and use emery cloth to wash the terminal and washers. Use a wire brush on the bolt. Clean the surface of the metal where the opening is drilled. Reassemble and tighten firmly. The same fault can occur on both headlamps once they are interconnected. However, when both lamps are dim, another possible cause is rust under the locating flange of 1 or both of the bulbs. Clean away dirt and corrosion wherever you discover it.

Total failure of all the headlamps – both main and dipped beams on each side means a failure within the feed to the most lighting switch or between that and therefore the dip switch. Where there’s a fuse fitted within the headlamp circuit , check it to see if it’s blown (See working on the wiring system ).

Circuits are often overloaded by adding extra driving lamps, or installing bulbs that are too powerful within the main lamps. Another possible explanation for fuses or lamps blowing may be a faulty transformer (See the way to test a automobile battery ) within the charging circuit.

Testing a sealed-beam unit

Use a clear test lead with crocodile clips to link the world terminal on the battery to the world append the sealed beam. Connect the crocodile-clip end of a circuit tester to the live battery terminal, and touch the probe to the other terminal or terminals on the sealed-beam unit in turn.

Use the car headlamp switch within the right positions. A sealed-beam unit with three terminals contains filaments for both main and dipped beam; if it’s only two terminals, one is that the earth and therefore the other works on main beam only. If any live terminals don’t work, the lamp has failed. If all of them work, check the connector block and wiring back to the snap connectors on the cars main wiring loom.

Testing the headlamp connectors

The connector block at the back of the headlamp may be covered with a large rubber protector. Prise it off complete with the two-pin or three-pin multiple plug. Switch the headlamps on. Connect the world lead of a circuit tester to a suitable earth, like the car body, and with the probe check each of the connector terminals in turn.

One of them is that the earth. If there’s just one other terminal, it’s for the most beam. If there are three terminals altogether, the connector is for both main and dipped beam. Use the car’s headlamp switch to see all the terminals. If any of the positive terminals don’t work, check the wiring and therefore the snap connectors back along the wiring loom to the bulkhead. Clean all the terminals before refitting.

Checking small bulbs

If one of the smaller lamps on the car fails to work, check whether the bulb is sound; if it’s , check the fuse (See Checking and replacing fuses). Never connect a plain test lead from a lamp-fitting terminal to earth. this may cause a brief circuit and fuse failure. Always use a circuit tester or a voltmeter to check a fitting.

If the fault is within the bulb, usually it’s possible to see a break within the filament, which can be amid blackening of the glass. There are many types of bulb in use — threaded types known as LES and MES; bayonet types with a center contact (MCC and SCC); a bayonet type with quite one filament and quite one contact (SBC); and a wedge base or capless bulb which is employed mainly for panel lighting, sidelights and number-plate illumination.

One of the later types is that the festoon bulb, which is employed mostly for interior lighting, but also in direction indicators and sidelights on some continental cars. Obtain the right replacement bulbs, as laid out in the car handbook — the incorrect bulb might not work properly or might not slot in the holder, and there are legal restrictions on the facility of bulbs used surely functions.

The SBC bulbs with double filaments utilized in brake lights have offset pins in order that they will only be fitted the right way. If there’s any doubt a few bulb, check by connecting it across the battery terminals. Use separate test leads from each terminal on the battery to the acceptable point on the bottom of the bulb. If bulb and fuse are both sound, or if the fuse blows repeatedly, search for a loose or broken connection causing a brief circuit, or a poor earth connection.

Testing small bulbs

To test a small bulb, connect a test lead from the world terminal on the battery to the bulb stem casing, and touch the bulb’s pole connection to the live terminal of the battery. Test a capless bulb by attaching two results in the exposed wires on the glass casing. If the bulb doesn’t light, discard and replace it. even if the filament appears to be intact, there must be a visually undetectable fault.

Testing multiple clusters

To test a push-in removable bulb holder, remove the holder with its connected wiring from the rear of the lamp fitting. Test the bulb separately to form sure it’s sound, then refit it to the holder.

Connect a test lead from the holder to a suitable earth on the car body. Operate the switch to the sunshine in question. If the light now works, while it didn’t previously, the lamp fitting within the car body is badly earthed. The fitting could also be earthed where it touches the body, or there may be a separate earth strap bolted to the body. search for dirt, corrosion or loose connections. Clean and refit the world connection, employing a wire brush and emery paper.

Carry a ‘lights’ first aid kit on the road

Because it’s an offense to not have lights working properly, it’s advisable to hold a small selection of bulbs within the car. Keep the bulbs in a tin full of foam rubber to avoid damage. Your car manual should tell you which of them bulb your car uses.

Use a small tin box, like a tobacco tin. Line the bottom with a thin piece of foam rubber, cut slots to carry bulbs during a second layer of froth rubber, and cover with a 3rd layer. Keep halogen bulbs during a separate container and avoid touching the glass.


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