Car Components Electrical Systems 

Fixing a simple light cluster

A simple light unit is one mounted individually on the bodywork. Depending on the model of car it can include indicators, side repeaters, sidelights, front and rear fog lights, reversing lights and even the main headlights and rear lights. It is essential to keep your car lights in good working order all the time. Apart from being dangerous, a defective light may also be illegal. If you do find a defective light unit, and you know the bulb is not at fault, the problem may lie in the light unit…

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Car Components Electrical Systems 

Update your charging system

Move the existing bracket forward to a new mounting point. Extra longbracket Fit an extra-long bracket to the original mounting point. Steel tubeextension Extend the alternator mounting point with a length of steel tube. Simple mounting If there is a second mounting point on the engine block, or if you can buy and fit a conversion bracket, offer up the alternator to its mounting points. It should fit snugly, but you may find that the rear mounting point on the alternator does not butt up to the bracket on the…

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Car Components Electrical Systems 

Checking the electrics with a multimeter

The range of meters on the market varies from simple dwell meters and tachometers to multi-function meters with up to ten different scales and even digital readouts. The meters shown above feature: A Sparktune: dwell, volts, ohms. B Autoranger: dwell, volts, ohms, amps, tachometer. C Testune: dwell, volts, ohms, amps, tachometer. D Hawk: dwell, tachometer. E Avometer 2003: volts, amps, ohms. F CAB-100: battery tester. One way of checking the electrical circuits is to use a simple test lamp connected between the circuit live wires and earth, but this method…

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Car Components Electrical Systems 

Renewing alternator brushes

Remove the brushes together with their terminal strips and springs. Unlike dynamo brushes, alternator brushes normally last for several years. Electrical arcing between brushes and commutator, a major cause of dynamo wear, is far less common. Alternators carry only the field current of 2 or 3 amps. The brushes are in contact with slip rings, which have a smaller, smoother surface than a dynamo commutator. The slip rings are solid rather than segmented, as in a dynamo. The clicking over the segments is another cause of brush wear in a…

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Car Components Electrical Systems 

Removing and refitting a dynamo pulley

If the dynamo is still on the car, free the nut before taking the fan belt off. The most common reason for removing a dynamo pulley is to fit it on a new dynamo — most replacement dynamos are supplied without one. When refitting an old pulley, or fitting a new one, be careful not to bend or damage it. The surfaces inside the V where the belt runs must be smooth. In many cases the pulley incorporates the dynamo cooling fan: its fins must not be bent or broken….

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Car Components Electrical Systems 

Cleaning and replacing a control box

Generally the dynamo control box is mounted on the front wing not far from the dynamo. But it may actually be on the dynamo or on the bulkhead, or even at the back of the dashboard. Many control boxes have resistors mounted on the baseplate. On cars with dynamos, faults in the control box show up in various ways, some of which are described in Testing a dynamo and checking output. Others may be revealed by the ignition warning lamp. If the lamp does not go out as the engine…

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Car Components Electrical Systems 

How to test a car battery

Check the electrolyte in one cell at a time. Put it back in the cell that it came from. Check the battery’s state of charge with a hydrometer , which measures the strength of the acid in the electrolyte, or battery fluid. This gives no clue, however, to the battery’s capacity – its ability to sustain a charge well enough to perform its tasks. Battery capacity depends on the size and number of the plates in each cell. If any plates are damaged, that cell’s capacity is reduced. The electrolyte…

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Car Components Electrical Systems 

Overhauling a light cluster

Start by carefully releasing the lens fixing screws. If the screws are tight, spray them first with penetrating oil. Lift the lens away. On most cars there is a seal behind the lens. If your car has one, be careful not to tear it while you do this. Find how the cluster casing is fixed to the car body. Slacken and remove the fixings. Make sure you do not lose any washers or seals fitted behind them. If the wiring is still connected at this stage, pull the unit out…

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Car Components Electrical Systems 

Checking battery leads and connections

Loosening the bolt of a clamp connector. A faint click or total silence when the starter key is turned usually means that the battery is almost or completely flat. If, however, the battery is fully charged, the trouble is probably in the circuit between the battery and starter. Either way, lack of power is preventing the starter motor from working – though there may be just enough current to work the solenoid, which makes a faint click or chatter. If you suspect the circuit, look first at the battery-terminal connections….

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Car Components Electrical Systems 

Fitting a new voltage regulator

The Lucas ACR alternator, like many alternators fitted to British cars, has the voltage regulator mounted inside. This is possible because the modern voltage regulator is a sold-state device. When you have tested the charging system of a car fitted with an alternator, and the checks in How to test a car battery point to a fault in the voltage regulator, make sure that you need to replace it. The fault may be elsewhere. If the simple tests described here do not work, take the car to an auto-electrician; alternators…

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