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MODERN ELECTRICAL EQUIPMENT FOR AUTOMOBILES MOTOR MANUALS VOLUME SIX MODERN ELECTRICAL EQUIPMENT FOR AUTOMOBILES Arthur W. Judge Associate of the Royal College of Science, London; Diplomate of the Imperial College of Science and Techtwlogy (Petrol Engine Research); Whitworth Scholar; Chartered Engineer; Member of the Institution of Mechanical Engineers; Member, Society of Auto- motive Engineers (U.S.A.), A.P.S.A. (U.S.A.) SECOND EDITION CHAPMAN AND HALL First published I962 Second edition I970 Chapman and Hall Ltd II New Fetter Lane, London EC4P 4EE First issued in limp binding I973 © Arthur W. Judge I962, I970 ISBN-13: 978-94-011-6883-o e-ISBN-13: 978-94-011-6881-6 DOl: IO.1007/978-94-011-6881-6 This limp bound edition is sold subject to the condition that it shall not, by way of trade or otherwise, be lent, re-sold, hired out, or otherwise circulated without the publisher's prior consent in any form of binding or cover other than that in which it is published and without a similar condition including this condition being imposed on the subsequent purchaser. All rights reserved. No part of this book may be reprinted, or reproduced or utilized in any form or by any electronic, mechanical or other means, now known or hereafter invented, including photocopying and recording, or in any information storage and retrieval system, without permission in writing from the Publisher. PREFACE TO THE SECOND EDITION The necessity for a reprint of the previous edition of this Manual has afforded an opportunity of bringing the information in certain parts of the book up to date, by the addition of a new Chapter 13 which deals with the more important developments that have occurred in the interim. This method has been adopted in order to simplify and to expedite the preparation of the present edition. As with the other Manuals of the Series, the elementary method of treatment of the subject has been retained, but where considered necessary some theoretical aspects are discussed. The previous edition has been checked and where desirable certain minor altera tions and improvements have been made in order to clarify the text. There have been several important developments in electrical components and wiring methods since the last edition, the more interesting of which have included the wider use of electronics in the design and construction of certain automobile parts. Examples of these are the use of transistors, diodes and printed circuits on flat and flexible bases, notably for instrument panels, while minia turized versions of printed circuits are finding wider applications in automobile components, e.g. for alternator voltage control units. In order to assist the non-technical reader, for whom these Manuals were originally intended, a brief outline of the theory and applications of diodes and transistors has been included to help him to understand the circuits using these modern components. For those seeking further information some useful sources are given in the references at the end of Chapter 13. Amongst the new material given in the new Chapter the follow ing may here be mentioned: printed and miniaturized circuits; modern alternator design and performance; improved conven tional and transistorized ignition systems; new sparking plugs and batteries; quartz iodine head, spot and fog lamps; improved flashing indicator systems; multi-speed windscreen wipers; mag netic-pulse type speedometers and tachometers. An account is given of a new type of flexible optical cable which transmits light 7 8 PREFACE from a single source at one end to illuminate several distant small areas, e.g. on the instrument panel and on switches. In conclusion one would like to take this opportunity to acknowledge the co operation in the preparation of this revised edition of the following individuals and manufacturers, namely H. H. Jones, for his advice and useful suggestions, T. C. Hoskins (Joseph Lucas Ltd.), B. Summerfield (AC-Delco Division of General Motors Ltd. England) and D. A. Cooke (Smiths Industries Ltd. Motor Acces sory Division). ARTHUR W. JUDGE Farnham, Surrey I969 CONTENTS I. AUTQMOBILE ELECTRICAL SYSTEMS page 13 2. THE STARTING SYSTEM 31 3· THE CHARGING SYSTEM 67 4· IGNITION SYSTEM PRINCIPLES 125 5· COIL AND OTHER IGNITION SYSTEMS 152 6. THE MAGNETO 195 7· THE SPARKING PLUG 2II 8. THE AUTOMOBILE BATTERY 233 9· THE LIGHTING SYSTEM 261 10. AUTOMOBILE ELECTRICAL INSTRUMENTS 292 II. MISCELLANEOUS ELECTRICAL EQUIPMENT 316 12. WIRING AND INSTALLATION 346 13· LATER DEVELOPMENTS IN ELECTRICAL EQUIPMENT 359 INDEX 406 9 ENGLISH - AMERICAN GWSSARY AUTOMOBILE TERMS English American Aluminium Aluminum Anti-clockwise Counterclockwise Bush (metal) Bushing Carburettor or Carburetter Carburetor Car Bonnet Hood Colour Color Contact Breaker Breaker Current Regulator Current Regulator or Limiter Relay Cut-out Cut-out Relay Dismantling Disassembling Dynamo Generator Earth (metal) Ground Fibre Fiber Gauge Gauge or Gage Headlamp Aligners Headlamp Aimers Inlet Manifold Intake Manifold Instrument Panel Instrument Cluster Assembly Licence Plate License Plate Lb. per sq. in. PSI Motor Car Automobile Moulded Molded M.P.H. MPH Paraffin Kerosene Petrol Gasoline Reversing Light Back-up Light R.P.M. RPM Screwed Threaded Spanner Wrench Sparking Plug Spark Plug Starting Motor Starter or Starting Motor Vice Vise Voltage Regulator Voltage Regulator or Limiter Relay Windscreen Windshield Wing Fender 11 CHAPTER I AUTOMOBILE ELECTRICAL SYSTEMS THE modern electrical system has been developed, over a period of some fifty years from the days of the early motor-car which usually had only one electrical system, namely, that of the ignition comprising either a trembler coil and battery or a magneto. The replacement of the magneto by the coil ignition system with its necessary battery unit, necessitated some means of keeping the battery charged and this brought the dynamo into more general use. Having a regularly charged battery the earlier advantage taken of this unit was to provide electric current for the headlamps and tail lamps and, later, to the electric motor starting unit that relieved the starting handle of most of its duties. From these early beginnings, the modern more complex auto mobile electrical system has been developed. This system involves the use not only of purely electrical devices, but also mechanical and optical ones, so that the modern motor engineer and mechanic must be familiar with the principles of electrical, mechanical and optical subjects. Basic Principles The present-day automobile electrical system may be regarded, broadly, as a transportable power station consisting of a petrol or Diesel engine, a part of the output from which is employed to drive an electric generator-which will be here termed the dynamo-to provide the source of electricity. Since it is necessary to draw electric power from the system at low road speeds and also when the car is at rest with its engine stopped, there must evidently be some kind of electrical energy storage unit, namely the -accumulator or battery. Thus, the engine-driven dynamo keeps the battery charged under all road running conditions, and the various electrical units of the automobile take their current supply from the battery. 13 MODERN ELECTRICAL EQUIPMENT The electrical system may be likened to that of an hydraulic system, consisting of a power-driven pump which draws water from a lower storage tank and pumps this water up to a reservoir or accumulator at a much higher level, thus creating a 'pressure head' which provides hydraulic power for operating various purposes, e.g. hydraulic motors for power purposes, hydraulic circuits, cooling systems, etc. It will thus be apparent that the reservoir acts as a power storage device in the same manner as an electrical accumulator and must be maintained at its required pressure head and water quantity by a power-driven pump. In this hydraulic parallel the pressure head and water quantity available are analogous to the electrical pressure, or voltage and the current supply. Automobile Electrical Systems To the beginner, the electrical wiring diagram of a modem auto mobile is apt to prove rather confusing, with its many electrical components and numerous circuit-indicating lines. This is due largely to the relatively large number of electrical components with their cables and also to the fact that invariably all of these components have a common origin of electrical supply, namely, the battery. As it would, of course, be very inconvenient to connect every electrical item to the battery terminals, instead, connections are made to certain other components, such as the voltage or voltage and current regulator of the dynamo, or to a distributor unit conveniently mounted for making the necessary connections. The battery is therefore provided, as a rule, with two main cables leading to the heaviest current consumer, namely, the electric motor used for rotating the engine crankshaft, via the flywheel, for starting purposes. The live lead or cable from the battery is taken to the starting motor switch, from which it goes, to the ammeter terminal, from the other terminal of which a lead is taken to the ignition switch and thence to the distributing device, i.e. the dynamo regulator unit and/or, a separate dis tributing component which supplies live current, through suitable switching units to the various electrical circuits that make up the complete electrical system. There is one important point that should always be remembered AUTOMOBILE ELECTRICAL SYSTEMS ) 5 when studying automobile circuits, namely, that all electrical components which draw their current from the battery are always connected in shunt (or parallel) with the battery via the live lead to the current distribution unit. Further, with the possible exception of the high tension (voltage) ignition system and the car radio both of which systems are initiated by battery voltage, all the electrical components of automobiles are operated at battery voltages, i.e. 6, 12 or 24 volts. Insulated and Earthed Return Systems In the case of domestic and industrial wiring systems all com ponents are connected or wired with twin insulated cables, the mains voltages being of 230-240 volts. In the earlier automobile wiring systems fully insulated cables were used for the electrical components, but latterly this method has been wholly replaced, for automobiles, by the single wire, or earth return method. Thus, a single insulated, or live cable conveys current from the insulated terminal of the battery, while the metal members of the engine and chassis provide a common return path for the various components, to the earthed terminal of the battery. Starter switch Battery + A Starter FIG. I. Schematic arrangement of car starting system Referring to Fig. I, which shows, schematically, the simple circuit of a car engine starting motor, the connecting lines denote insulated cables. If, however, the return current conductor AB is connected to the metal of the car, this will not affect the flow of the current, so that the return cable can be dispensed with if the positive terminals of the starting motor and battery are