Careful attention to electric systems
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BECAUSE electricity is a natural phenomenon and therefore has no national boundaries, commercial vehicle electrical circuits all follow the same principles, whether the vehicle has been produced by an Englishman, Dutchman, German, Japanese or anyone else.
The manufacturer will, at the design stage, always try to anticipate the operators requirements and build in a reserve for specialist electrical equipment, but unfortunately in many cases the quality of the standard equipment leaves a lot to be desired.
Rear light clusters and cables are a classic example where they are not adequately shielded and left exposed to moisture, dirt and road salt. The additional initial cost would be minimal compared with the aggro of light failures and wiring problems.
It takes several years of training to become a specialised vehicle electrician but there are many jobs that a mechanic can carry out on the vehicles in his charge provided that the job is given a little forethought.
To obtain reliable service from a vehicle's electrical systern it must be regularly checked, preferably daily for the lights and at the same time as a mechanical and lubrication service.
Electrical equipment manufacturers are usually able to provide sets of wall charts giving diagnostic procedures for the various systems found on commercial vehicles and provided that the recommended procedure is adhered to, then no problems should be encountered.
With today's marketing methods, major items of equipment are obtainable as service units only and trying to obtain individual parts can be very difficult.
One big drawback with this system is that for instance, if an alternator has failed, trying to locate a replacement unit can be a nightmare, particularly for imported vehicles, because the manufacturers' stockists always appear to be out of the stock.
This means that the operator has to make numerous telephone calls trying to locate a unit when, in all fairness, it is the stockists' problem and ought to be done for him.
With petrol engine vehicles the majority of failures arise in the ignition system and caused by dirty or loose connections. It is very important that the spark plugs are renewed at the plug manufacturers' recommended mileage even though they look all right and the electrodes still have -a little left on them."'
Do not be tempted to use plugs other than those recommended by the manufacturers.
Electrode gaps must be correctly set using gauges and not one's thumb nail.
The distributor is usually in an inaccessible position, so is often forgotten. This is obviously wrong — it must receive its correct attention. Contact breaker points must be clean and set the recommended gap using feeler gauges. Like the spark plugs, they must be renewed at the recommended time because the fibre or plastic heel has a habit of wearing down, particularly on the modern quick-fit type.
It is known for this type to lose all its adjustment on a motorway journey, so lubrication of the cam is of paramount importance. Often forgotten are the rotor arm tip and segments in the distributor cap. These must be left clean of any buildup caused by tracking.
While dealing with the ignition system, check the cleanliness and security of all terminals and connections. If intermittent firing is experienced and carbon-impregnated ht leads are fitted, check by substitution as this lead is prone to internal failure, which is not apparent by inspection.
The alternator/dynamo drive belt must be checked for correct tansion at the mid-point of the longest run. The condition of the belt must also be regularly checked as failure not only affects the charging system but also the cooling system on many engines.
If there is a fault in the charging system, the only way to find the cause is to check, using a moving coil voltmeter and ammeter, so that an accurate adjustment may be made.
The battery is often forgotten until the engine does not start on a cold morning. The terminals must be left clean and the cells topped up with distilled water — not tap water. A dirty battery will cause discharge between the two terminals, so cleanliness is important.
Time spent checking the lights and lenses is well spent. Any sign of condensation indicates a failed seal and this should be repaired using DumDum or plasticine if a new seal is not available. Bulbs that have blackened only have a short life left, so renew them.
Do not forget the trailer light multi-pin connectors, as these suffer from road salt corrosion. A slight smear of grease prolongs connector pin and socket life.
Check all the wiring systematically and make sure it is firmly clipped to the chassis c body. Any cables rubbing on part of the chassis cros: member should be secured.
Steam cleaning before th DoE test causes havoc wit electrical equipment, so chec that the operator is not ove zealous in his cleaning activitie:
Fuel gauges and tank uni. have a habit of suddenly givin inaccurate readings. Thes usually are renewed in pairs — simple job. Always check thu the fuel tank sender unit gaski is not leaking and renew necessary. Fuel leaks are e; pensive.
Manufacturers are no making multi-part wiring ha nesses, so if there is a failure c damage, then only a section he to be replaced. Such items E. the steering-column switche are supplied with their wiring u to the multi-pin connector. Tff makes replacement easier.
Simple switches can prov difficult to remove because the are sometimes held in positio with special leaf clips. To releas the clip, a special tool i necessary unless the originE clip is broken and a new clip is t be fitted.
Specialist equipment mu; be serviced according to th manufacturers' instructions. must be fitted with the correc capacity and colour-code cables. The manufacturer wi supply all the relevant informE tion with the fitting instructionE Coaches have the most corr plicated electrical systems vehicle electrician could wis for. However, coach bod manufacturers have in man cases been considerate an made access to the main contrc board relatively easy.
Unhappily, the days of fittin fuses to every electrical circu are over — only the minimur are fitted now. For this reason, is of paramount importance t keep the electrical system first-class condition. If allowel to deteriorate, it will only caus a failure on the road at a mos inconvenient time or even wors still, a fire.