Lucas Vehicle Wiring Circuits Technical Service Manual
Contents
1. E_ will prefer to chop the old harness out piecemeal and run his new wiring direct in situ Whichever method may be employed a thorough and final check is necessary when the rewire is com pleted in order that a clean and effective job is assured This final check should comprise the following Operations l Replace the charged battery on the vehicle making sure that earth connections are clean and tight leave the main battery lead off Check that oil pipes speedometer drive etc are properly connected 3 Check that ALL switches are in the OFF position and that no odd leads are left disconnec ted 4 Connect the main battery lug but do not tighten this facilitates emergency removal Switch on ignition and start engine 6 Check the charging Check all lights in turn Check all accessories in turn If everything is in order tighten the main battery lug tO ri Oo oO N SUMMARISING Whilst it is not possible to cover every variation in circuit arrangements that a particular vehicle manu facturer may adopt the various circuits which have been provided in this book represent the standard layout employed for most vehicles If these are properly understood very little difficulty will be experienced when confronted with the wiring atrange ment on occasional special models or even on new model cars now being produced Such arra2. LIGHTING amp IGNITION SWITCH SLR LAMP SLR LAMP SWITCH SNAP CONNECTORS MAIN BEAM p WARNING LAMP THE LONG RANGE DRIVING LAMP The most satisfactory arrangement for installing this lamp is such that when the head lights are dipped the SLR lamp should automatically go out thus avoiding the necessity for two separate operations This result can be conveniently obtained by taking a red and blue 28 012 cable direct from the main beam terminal of the dipper switch An additional hand control switch may then be inserted in this feed line to enable the driver to have the SLR on with bis head lamps on main beam With this arrangement the lamp will immediately go out when the head lights are dipped FOG AND PASS LAMPS When fitted as initial equipment fog and pass lamps will usually take their current supply from the S or T terminals on the lighting switch so that they may be automatically switched off with the side lamps If such lamps are fitted subsequently this is still the most suitable method It is usual to wire these lamps by means of a red 28 012 cable from the lighting switch to the lamp switch and follow with a red and yellow 28 012 to the lamp itself making quite sure that the lamp has a good earth If there is any doubt about this a separate black earth wire should be installed The relatively large size of cable is necessary if full brilli ance from the lamp is to be assur
3. system are the generator control box and battery That part of the circuit connecting the battery with IGNITION the control box has already been dealt with as the ariii brown battery supply circuit The generator circuit itself consists of a yellow 28 012 cable from generator D terminal to ITT aay control box D and a yellow green 14 012 from generator F terminal to control box F alk Additionally there is a yellow 14 012 cable con ee necting from control box D to one side of the j oe Oar ignition warning lamp ee OYNAMO BROWN 2 GUE ead 4 YELLOW THE IGNITION WARNING LAMP This indicator lamp performs two functions from terminal A3 at the switch through the warning l It indicates that the battery current is switched on lamp to the D terminal of the generator the circuit to the ignition and ignition fed accessories being completed through the generator winding to is earth The lamp therefore lights up 2 It indicates that the generator is charging when Orhan ad fanme is aated and DE ARG engine is turning at charging speed rae D Meen he bith voltage builds up to 12 volts it opposes and equalises Follow the previous circuit through Commenting the battery voltage previously applied to the lamp and at the A3 terminal of the ignition switch an extension no current will flow through it The light goes out of the white lead is carried to one side o
4. Wiring Principles Simple Wiring Circuit Earth Return System Negative Earth System Positive Earth System Connecting Up and Terminal markings Methods of wiring Cable looms Junction boxes Types of cable in use Starter cables Ignition cables Current carrying capacity PART 2 Individual Wiring Circuits Circuit Identification Typical wiring circuit Wiring diagrams Starter circuit Manual switch Relay switch Ignition circuit Charging circuit Ignition warning lamp Rear lighting Head lighting Panel lighting Driving lamps Fog and Reverse lamps Auxiliaries Trafficators Screenwipers Fuel gauge and petrol tank unit PART 3 Rewiring in Service Cable stocks Sizes Colours Protective sleeving Snap connectors Junction boxes Partial rewiring Complete rewiring Methods of rewiring QUESTION AND ANSWER PAPERS STUDENTS QUERY PAPER AIR MAIL REPLY ENVELOPE www lassicCycles org JOSEPH LUCAS SALES amp SERVICE LTD BIRMINGHAM ENGLAND Page 3 ClassicCars amp C Wiring Principles lassicC ycles org SIMPLE ELECTRICAL CIRCUIT The typical electrical circuit as we know it com prises any component such as a lamp for example connected to a supply which may be a battery by two wires or cables a feed wire and a return Any electrical installation employing this arrangement is known as an insulated return system and for some time the el
5. connecting through one or more snap connectors 3 to the petrol tank rheostat 4 The circuit is completed through this unit to earth In the event of any erratic reading on the gauge the first thing to do would be to check the terminals for tightness and open and remake the joints at the snap connectors because either a loose or corroded con nection will seriously affect the operation of the tank unit rheostat Page 16 FUEL SCREENWIPER SWITCH FUEL TANK UNIT RF 95 CONTROL BOX Classic Cars amp Cycles THE AUXILIARY CIRCUITS A AND A2 ON CONTROL BOX This picture shows a fairly typical layout for auxili aries which are not under the master control of the ignition switch and which may vary somewhat on different vehicles Top centre of the picture shows the inspection lamp sockets and a cigar lighter It is usual to place these in the battery feed circuit before the ammeter It would serve no useful purpose for the heavy current discharge from the cigar lighter to register on the ammeter it would merely tend to alarm the driver Similarly if the inspection lamp is dropped and shorts as a result of bulb breakage this would probably damage the ammeter On the other hand a radio set for instance which will have its own fuse may be left on accidentally or it may be in circuit for prolonged periods It is therefore desirable that the discharge should be shown on the ammeter Similarly with heayy curre
6. engine chassis and body before final assembly It will be readily seen therefore that these harness sub assemblies play an important part both in the initial layout and later in service where rewiring of a damaged section becomes necessary Let us now consider the means of identification of this multiplicity of cables As we have stated the electrical system is a series of simple circuits each consisting of the component its switch and three wires feed switch wire and return The Lucas colour scheme of identification for British cars is based upon this principle Feed wires carry braiding of a main colour only switch wires have a main colour of feed with a coloured tracer woven spirally into the braiding and return or earthing leads are black These then are the basic principles which will be enlarged upon in the following pages of this section of the course For the administrator and store keeper the sections dealing with cable sizes their current carrying capacity protective sleeving rubber grommets will be found invaluable as a general guide when considering the materials to stock particularly where the rewiring of vehicles is an essential part of the service offered In compiling this section on wiring circuits as installed on modern British cars we have reduced the technicalities of the subject to a level that should be easily understood by all students Classic Cars amp Cycles www C lassicC ycles org CONTENTS PART 1
7. for the auxiliary circuits which are fed from the ammeter and protected by a fuse A2 The Ignition Circuit The Charging Circuit Lighting Circuits h e WwW Y Accessories Circuit appropriate coloured tracer I Plain brown cable or brown with coloured tracer in it is used as the current supply or feed wire to all services 2 White for the ignition circuit and all component feeds which are essential when the ignition is switched on 3 Yellow or yellow with coloured tracer is used for the generator and field circuit 7 Green is used for the auxiliary circuits which are fed through the ignition switch and protected by a fuse A4 8 Black is used for the earth circuit That is ifa component is not fixed directly to the chassis a cable must be taken to a good earthing point on the chassis and this cable will always be black THE TYPICAL WIRING CIRCUIT We can now deal with the wiring circuits as applied to modern vehicles Generally the electrical system of a motor vehicle can be considered as a series of simple circuits each consisting of the component 1 its switch 2 and three wires comprising the feed switch wire and return 3 this return being provided by the frame of the vehicle although in the case of components insulated from the chassis an earthing lead is also necessary Some variations are to be found such as fuses two way switching and so on but the principle of feed
8. in making the work more profitable Finally although such work may have to be carried out by relatively inexperienced personnel a good quick job can only be expected from an experienced electrician At the same time practice will soon result in increased speed and proficiency CABLE STOCKS SIZES AND COLOURS The following cables constitute the minimum range necessary Quantities can be adjusted to suit the conditious and volume of work availability etc The essentials extracted from our Catalogue No 502F are as follows Starter Cables 1 37 20 for the 12 volt system 2 61 20 for the 6 volt system 3 61 18 for heavy C V work 4 Earthing braids Circuit Wiring Cables 5 44 012 max 22 amperes brown 6 28 012 max 4 amperes yellow blue white purple and black 7 14 012 max 7 amperes red green white and yellow When all the coloured cables are not obtainable short lengths of coloured sleeving will aid identifi cation Ignition Cables 8 7 m m H f Neoprene UM 827 For motor cycle wiring 5 m m Low Tension and miscellaneous pur gt rubber covered poses Multi Core Cables An assortment of these is essential for steering column re wiring and they are available with from two to seven cores according to requirements PROTECTIVE SLEEVING AND RUBBER GROMMETS It is essential that all new wiring should be pro tected against chafing and exposure at vulnerable points For th
9. to the common earth point on the chassis THE INSTRUMENT PANEL LIGHTING The last item is the lighting on the instrument panel This is generally fed from the sidelamp terminal on the lighting switch On this model a red feed cable commencing from the lighting switch 1 supplies the panel switch 2 and this loops as a red and white cable to a snap connector and the individual panel lights In this case there is no separate earth cable From the panel switch 2 there is a red and green cable 3 which feeds the interior lamp 4 and also an earth cable 5 which is a black cable direct to the chassis Notice that the interior light is wired directly to the panel light switch but generally interior lights are fused taking their supply from the A2 fuse is PANEL LAMP CIRCUIT Page 13 ClassicC ars amp Cycles THE COMPLETE LIGHTING CIRCUIT Here we have the wiring diagram of the complete lighting installation we have seen just how stmple this is by breaking it up into individual circuits www C lassicC ycles org a INTERIOR O HEAD SIDE 8 P PANEL LIGHTS e LONT SS TAIL LAMP gt SWITCH RF CONTR 12 VOU BATTERY OL BOK Tae F FROM Ct IGNITION a Oe a Po SWITCH amp llo UGHT NUMBER PLATE star i nevense LAMP ETOP LTAIL ATAIL oF STOP LAMP SWITCH DIPPEA CS gt E a SSE i i MA LAMENT M PLAMENT FILAMENT ANY aa gm MAIN LIGHTING CIRCUIT
10. wie RACK EN wick WHITE 4 BROWN er ATO 47 FED na BACWN 7 BASE wnt mur wort GALEN mih PUARE JS oS rT d BARD oun MACK Bi BLACK wich verri WWATE kAafO D aA AMOC FLAGE wus cae m 12 VOLT 1I WISTE wha YELLOW 34 CALLN wish SLACK 3D BACH wich W 50 PURILE with REO 4 OLACK h PAPE TL WISTE wih PLUE zu cow ACADA St PURE a Saas hab The LAO WN oly WHITE een GECON 26 YELLOW wth ALD P OWN her PURRE SP PUAPLE wre ISSUED JUNE 1948 NUMBERS INDICATE CABLE DENTIFICATKIN COLOURS SCE KEY ABOVE FOR SPECIFICATION OF EQUIPMENT SEE OVERLEAF HEAO siot amp TAIL LAN JwT COMMON BATTERY SUPPLY CIRCUIT ep NITION The current supply for all circuits on the vehicle en commences either direct from the battery negative terminal or from the battery side of the starter switch It comprises a heavy brown cable first running from the battery to the control box A terminal and through the load windings of the regulator to the terminal Al From here a brown and blue cable leads to the lighting switch where it loops off to one side of the ignition switch terminal A If an ammeter is installed it will be placed in the brown lead between the source of supply and the control box A terminal the cable becoming brown and white between the ammeter and the control box AF 95 CONTRO BDr THE BATTERY SUPPLY CIRCUIT Eee Page 10 Classic Cars amp Cycles www_C lassicC ycles org THE STARTER CIR
11. 7 The accessories This general check over will take about a quarter of an hour Remove any units which may require attention in the way of overhaul or minor repatcs The main job of re wiring the vehicle can then be tackled Page 19 Classic Cars amp Cycles METHODS OF REWIRING Where only inexperienced labour is available the best method is to disconnect the leads from their components and then remove the complete harness intact if possible 5 During the removal of the main harness some de cision will have to be made as to whether such additional cables as trafficator leads interior ligbts etc which are in the overhaul require renewing Generally this will not be necessary On the other hand the leads passing into the steering column assembly will almost invariably need replacing Some care should be taken over this as such rewiring necessitates the use of the correct multi core cable Lay the harness carefully on a suitable size bench and position it with a few stout nails to act as locating pins A complete new set of cables can now be run using the old loom as a pattern Tie the cables together at junctions and apply sleeving where required Finally re assemble the complete new harness on to the vehicle and re connect to the components The more experienced man who fully understands his circuits and is thoroughly familiarwith the work www C lassicC ycles org a eC re EE
12. CUIT WITH MANUAL SWITCH The first and most elementary circuit is that of the starter motor system This motor can be either manually or solenoid operated Our picture shows the manually operated starter motor circuit The current path is from the negative terminal on the battery to the starter switch 1 across the switch contacts to the insulated terminal on the starter motor 2 through the starter to the engine block then via the bonding strip to the chassis 3 returning to the positive terminal of the battery via the battery earth cable 4 The earth cables 3 and 4 are most important to the successful operation of the starter particularly under cold starting conditions and must always be well maintained Where a solenoid starter switch is fitted an addi tional relay circuit is introduced STARTER STARTER Sw STANDARD STARTER WITH MANUALLY OPERATED SWITCH EAD SIDE THE STARTER CIRCUIT SOLENOID RELAY OPERATED In this arrangement of the main starter circuit we have to add a solenoid operating circuit and this is under the control of the ignition switch That is the starter solenoid can only be operated with the ignition switched on Firstly there is the common supply from the battery to the ignition switch for all the circuits Our solenoid supply is taken from the other side of the ignition switch A3 to the solenoid operating push by a white cable and from this push to the solenoid wi
13. ClassicC ars amp Cycles www C lassicC ycles org TECHNICAL SERVICE OVERSEAS TECHNICAL CORRESPONDENCE COURSE Section 6 VEHICLE WIRING CIRCUITS JOSEPH LUCAS SALES amp SERVICE BIRMINGHAM 18 Page 2 ClassicC ars amp Cycles www C lassicC ycles org INTRODUCTION The electrical circuit of the modern automobile can appear most complex to the uninitiated Careful study however of the wiring diagrams produced by the Lucas Organisation and the Vehicle Manufacturers will allow the student to study the various circuits both individually and asa whole The study of ach circuit separately before tackling the complete job is perhaps the best method for the student to adopt as with few exceptions the electrical system of a motor vehicle can be considered as a s ri s of simple circuits as for example the Lighting Charging and Ignition circuits Having grasped the fundamentals of these circuits it is then possible to consider as a whole the complete Wiring Harness or Wiring Loom Motor vehicle wiring has been and continues to be subject to many changes mainly to facilitate speed and convenience on the vehicle assembly lines With the introduction of snap connectors and separate junction boxes cable assemblies can now be made up as subsidiaries to the main loom This considerably assists the manufacturer whose vehicle in these days of mass production is often produced at separate branch works in the form of units i e
14. In the case of the reversing lamp the feed comes off the second snap connector 6 and proceeds still as a green cable to the reverse lamp switch 7 usually mounted on the side or end of the gearbox and actu ated when the reverse gear is selected From the switch the switch wire proceeds as green and blue via another snap connector 8 direct to the reverse lamp 9 and thence to earth 10 through the bulb www C lassicC ycles org RF 95 CONTROL BOX STOP LAMP ER SWITCH f eee e m REVERSE LAMP SA G 6 SCREENWIPER SWITCH Q TO FUEL Gauct RF 95 CONTROL BOX SCREENWIPER THE SCREENWIPER CIRCUIT A second green feed wire from the A4 on contro box 1 is used to supply the screen wiper and the petrol tank unit This wire runs direct to one side of the screenwiper motor switch 2 which also acts as a junction point for the feed wire to the fuel tank unit From the other side of the switch the wire becomes green and yellow to one side of the screenwiper motor 4 From the other terminal on the motor 5 the cable iss black return to the E terminal on the control box direct to a good earth on the chassis 6 THE FUEL GAUGE AND PETROL TANK UNIT As previously stated the green feed wire for this component is junctioned off the screenwiper switch 1 From there it connects still as a green cable to the fuel gauge unit 2 From the gauge the colour changes to green and black
15. cable manufacturers describe their cables in terms of standard wire gauge and this illustration shows the equivalent sizes which will carry the same amount of current For example Our 44 012 will compare with 44 strands of 30 SWG wire or 100 strands of No 36 SWG ail having the same cross sectional area of copper which determines the amount of current which can be carried with a specified minimum voltage loss i e voltage drop www C lassicC ycles org CAR TYPE CABLES 9 012 30 SWG EQUIV 23 36 14 012 30 SWG EQUIV 40 36 28 012 30 SWG EQUIV 70 36 44 012 30 SWG EQUIV 100 36 UM837 Rubber Neoprene covered Ozone tested Resistant to Heat Oil and Water Special Purpose 7mm Highgloss Braided S 4mm Smm Low Tension 7mm High Tension Page 8 IGNITION CABLES 1 The 7 m m high tension rubber cable is generally used for spark plugs and distributor or magneto leads There are numerous grades of this widely used cable at varying prices but it is always good policy to buy high quality in order to obtain maximum durability in service This avoids failures as a result of deterioration and cracking which may cause elusive and annoying misfiring or pechaps complete breakdown The top three cables shown in the illustration are Lucas H T cables which all use Neoprene outer casings This material has proved to be the best possible protection against heat oil petrol and Water T
16. ectrical equipment on vehicles followed this principle EARTH SYSTEM An alternative arrangement suitable for many applications uses an insulated cable as a feed wire to the component the return being obtained vta earth which on a vehicle is of course the steel chassis Such an arrangement reduces both the amount of cable necessary and the complexity of the wiring circuits This single pole or earth return system soon became standard practice for vehicle work in general But RETURN INSULATED RETURN SYSTEM for many of the larger vehicles such as passenger carrying and certain heavy commercials which include petrol carrying vehicles the insu ated return system is still used CHASSIS RETURN NEGATIVE EARTH SYSTEM FEED CHASSIS RETURN POSITIVE EARTH SYSTEM NEGATIVE EARTH SYSTEM With the earth return system the orthodox arrange ment was to earth the negative pole of the supply and this became known as the single pole negative earth system which was used for vehicle work for several years on British vehicles up to about 1936 POSITIVE EARTH SYSTEM It was then found that certain specific advantages were Obtained by earthing the positive pole of the battery instead of the negative Thus we had the introduction of the positive earth system which is alm st universally used to day except for those specialised vehicles previously mentioned One ofthe main advantages gained by earthing t
17. ed Page 14 LIGHTING amp IGNITION SWITCH FOG LAMP FOG LAMP SWITCH SIDELAMPS ClassicC ars amp Cycles AU XILIARIES There are three groups of auxiliaries and accessories which take their current supply from either the A3 A4 or A2 terminals on the control box Those supplied from the A3 and A4 terminals are under the master control of the ignition switch Since they are only required when the engine or vehicle is in motion this practice precludes the possi bility of their being accidentally left on and so running the battery down The unfused components supplied from the A3 terminal will comprise the electric petrol pump auto choke petrol reserve solenoids etc The fused components supplied from the A4 terminal consist of trafficators stop lamp reverse lamp windscreen wiper fuel tank unit demister and heater motors when fitted The A2 terminal and its fuse takes current direct from the battery through the oad windings of the regulator and is used for interior lights door lights low current horns The heavy current horns such as the wind tone models and also radio sets will preferably have separate fuses the initial supply being taken from the A terminal of the control box thatis directly from the battery and not through the load windings of the regulator There remain a few additional items which for special reasons may take current direct fro
18. f facilitating assembly both at the electrical manufac turer s works and also on the vehicle makers assem bly lines Next the cables are grouped together and braided into looms with individual conductors emerging where required thus forming main branch and trunk cables Tbe development of this arrangement not only facilitates assembly but also provides considerable protection against chafing on metal edges and sub sequent wiring faults in service Additionally sub assemblies such as the complete car body or say a steering column may be fully assembled and wired before being positioned on the vehicle To facilitate the fitting up various junction boxes and snap connectors are now widely used STARTER PUSH tht A CABLE LOOM H L SWITCH bs IGNITION On some vehicles one complete wiring loom may be wji used on others as many as four separate looms one main and two or three subsidiaries are needed and these are finally connected up to the main loom by means of snap connectors or junction boxes Alto gether there is a vast variety of wiring looms made up for different makes and models So unless the vehicle is specially laid out the stocking and general use of wiring looms is not practicable For this reason the renewal of damaged wiring is more easily and economically handled in service by putting in single cables and employing HEADLAMP either junction boxes or snap connectors to rejoin JUNCTION to
19. f switch on the steering column or alternatively by a similar type of switch on the panel The most usual run of this circuit is as follows A green cable 14 012 from A4 on the control box feeds to a iwin spring connector 2 Two leads branch from this connector one to the stop lamp switch the other to a further spring connec tor 3 located at the bottom of the steering column From here one lead branches off to the reverse lamp switch the other to the trafficator and horn switch at the top of the steering column 4 Two cables green and white and green and red lead from this switch and connect each to one trafficator through an additional spring connector 5 also located at the bottom of the steering column In the majority of cases a separate black earth lead will be run from each trafficator to an earthing point as shown at 6 Page I5 Classic Cars amp Cycles THE STOP AND REVERSE LAMP CIRCUITS We can now examine the stop lamp and reverse lamp circuits together You remember the common green feed wire from A4 on the control box branched away still continuing as a green cable from the first snap connector 1 for the stop lamp This further green cable leads direct to the stop lamp switch 2 sometimes a small hydraulic switch mounted on the master brake cylinder From the switch it proceeds via a rubber covered snap connector 3 direct to the stop lamp 4 and thence to earth 5
20. f the warning and remains so until the generator ceases to charge light From the other side a yellow lead is taken and its voltage falls Battery current will then pass direct to the D terminal at the control box through the lamp again and it will remain alight When the ignition switch is closed current feeds until the ignition switch is moved to the off position SA Gann SwitcH separate red cable runs to each side Jamp via a snap connector 3 The return cable is b ack and you will notice that in this case it is a full return through snap connectors 4 to a special earthing terminal on the chassis 5 This was evidently required on this particular model to assure a good return path and it would be very necessary to check this if any trouble were experienced sO O E SIDELAMP CIRCUIT This picture features the sidelamp circuit Commencing at the lighting switch terminal 1 2 a i T ae l oi with the sidelamps gt i 4 S oaa 70 sion aM TR ai SIDELAMP CIRCUIT Page 12 Classic Cars amp Cycles REAR ILLUMINATION In this example the rear illumination comprises tail lamp one on each side and also the number plate box lighting comprising two bulbs Commencing at the S1 terminal on the lighting switch 1 from which the side lamp feeds are also connected another red cable runs directly to the first tail lamp 2 This red cable loops out again to a snap con
21. he positive stde of the supply is that the polarity of the spark plug central electrode is made negative which results in improved spark plug performance and longer service life of the spark plugs and the H T cables At the battery itself the formation of electrolytic sulphatton at the positive lug is reduced and also the marked tendency to electrical leakage from the cells to earth the result of the presence of acidulated moisture The corrosion effects at switch contacts cable connectors soldered joints etc are also reduced especially under conditions of excessive humidity CONNECTING UP AND TERMINAL MARKINGS A point to be remembered is that this reversal of polarity makes no difference whatsoever to the working of the system or testing for faults but it has to be borne in mind when fitting the batteries and connecting up cables Terminals are all properly marked without reference to the polarity as shown in our picture i e the dynamo and field terminals D F The D terminal being the larger of the two POSITIVE EARTH RETURN Page 5 ClassicC ars amp Cycles www C lassicC ycles org a L METHODS OF WIRING Now we come to the cables and the method of wiring which is generally by means of a harness We shall confine ourselves to British vehicles although most others follow the same general pattern Our picture shows a wiring loom in course of manufacture Multi coloured cables are employed as a means o
22. he 4and S m m low tension cables which will carry upto about 7 amperes are widely used for motor cycle work and are equally suitable for any exposed working conditions where the cable is not subjected to oil or petrol We have mentioned altogether ten cables com mencing at the heavy type starter cable carrying up to 700 amperes and finishing with the 4 and 5 m m mainly used on motor cycles These ten different sized cables together with earth braid constitute the minimum range which should be stocked for general motor work tl cassie C Thidivitfual Wiring Citetitss so THE WIRING CIRCUITS Whilst a car wiring layout as a whole may appear complicated at first sight the complete arrangement may be broken down into separate circuits as follows 1 Battery and Starter Circuits CIRCUIT IDENTIFICATION BATTERY IGNITION AND CHARGING To distinguish these circuits a distinctive colour scheme is used The value of such a colour scheme on the car assembly line is obvious and once it is understood it is of equal value in service fault finding So before we discuss all the wiring circuits we must know about the colours employed Eight basic colours are used as follows with an CIRCUIT IDENTIFICATION LIGHTING AND ACCESSORIES 4 Red for the side and tail lamp circuits starting from the lighting switch 5 Blue for the headlamp lighting circuit also starting from the lighting switch 6 Purple is used
23. is purpose the most generally suitable material will be lengths of oil proof plastic sleeving PVC which can be cut down to suit individual requirements The taping together of runs of cable is unsatisfactory in service and is instantly recognisable as bad work manship The following minimum range of six sizes will be required Page t8 Sleeving 5 m m dia to carry one cable E ra a y a Wa Cables IE w on three to four cables is 4 s a gt lt a to six Cables Pe seven to nine cables A tenand over Rubber Grommets 4 bore to fit 4 hole so os amp hole gy a 0 Sega ae See ClassicC ars amp Cycles JOINTERS SNAP CONNECTORS AND JUNCTION BOXES The comprehensive range of connectors and junc tion boxes illustrated tn our Cable Catalogue No 502F will cover all requirements www C lassicC ycles org ee a The only alternative to these connectors is twisted and soldered joints a slow business In no circumstances should dry joints be permitted These deteriorate badly in service and are visible evidence of bad workmanship CABLE CLIPS A good range of cable eyelets or terminals and also spring and screw fixing clips are other essentials to economical rewiring work and a comprehensive range is illustrated in our catalogue No 502F Typical samples are as follows 1 Junction Boxes These are available with 2 4 6 and terminal positi
24. m the battery Two popular ones will be the cigar lighter which takes a very heavy current and the inspection lamp sockets which may be required when every thing else is off We shall now examine all these auxiliary circuits individually commencing with the A4 fused auxiliaries under the control of the ignition switch www C lassicC ycles org FUEL SCREEN WIPER HEATER GAUGE SWITCH RHEOSTAT MEAD SIOE ge Q D OA imma O e T a ET HEATER MOTOR WHEN FiTTEO ae 12 VOUT Rat TERY caz s w A n o AA KDS SCREEN WIPER gt Lt STOP LAMP nO REVERSE Switcn 3 i 40 RAEVEASE Laue io Switch bas TAAFFICATOA ea TRAF FICATCA AIGHT mano PRAE PATOR LEFT nano aie Ne A4 CIRCUIT FUSED AUXILIARY CIRCUITS ON A4 Now let us examine these A4 circuits on an actual vehicle They are the most complicated of any and we shall consider each one separately As this picture shows there are ouly five altogether on this particular model 1 e Trafficators Stop Lamp Reverse Lamp Windscreen Wiper Fuel Tank Unit AN Wi I MITION SWITCH RF 95 CONTROL BOR re FR 2 FELO STOP LAMP Garin FECO REVERSE Lame 3 TAAFFICATOR _ TRAFFSICATOR RIGHT MANO poma Be CLEFT HANDO S 4 O SWITCH k a eee i lt eE kd t THE TRAFFICATOR CIRCUIT Trafficators are supplied from the A4 1 35 amp fuse local control being provided either by a self cancelling two way and of
25. nding by a white and red cable The winding is earthed to the casing of the solenoid itself thus com pleting the earth side of the circuit back to the battery earth STARTER CIRCUIT THE IGNITION L T CIRCUIT NOR A white cable commencing at the A3 terminal of SEA ROR the ignition switch is taken to the A3 terminal at the MITE LALO y piike rs control box and provides a common supply for the IGNITION 2 Q 9 Ep tee o B SWITCH a Ce ignition units coil and distributor together with all wk aans A ronen NS a DAT the ignition accessories fused and unfused SOLENOID AF 95 CONTROL BOK E i wintt se rit PETROL ume which are under the control of the ignition switch Using the A3 terminal on the control box as a junction point a white 28 012 cable connects directly to the SW terminal of the ignition coil A white and black cable joins the CB terminal of the gt ignition coil to the L T terminal of the distributor Sit an i N The unfused accessories such as the petrol pump and ey automatic choke will also be supplied from the A3 foam control box terminal using the white cable as the feed al L con wire ARS WHITE amp BLACK The ignition warning light feedwire also a white Bae cable is taken direct from the A3 terminal of the fi ignition switch Page 1 Classic Cars amp Cycles www C lassicC ycles org THE CHARGING CIRCUIT The main components involved in the charging ere
26. nector located in the luggage boot 3 From this snap connector two more red cables feed the second tail lamp 4 and the two bulbs wired in parallel in the number plate box 5 You will notice particularly that a black earth wire connects from both tail lamps and the number plate box to the earth terminal on the control box and thence to the chassis earth 6 www C lassicC ycles org LIGHTING SWITCH we AA Si E9 Tart Tail LAMP wumaeaj erate tP ILLUMINATION LAMPS eee a TDR mie is e3 CEO 0 O O Q amp BLACK REAR LIGHTING CIRCUIT HEADLAMP CIRCUIT THE HEAD LIGHT CIRCUIT We have already explained that all the main lighting current passes over the load turns on the voltage regulator to the lighting switch So we can commence at the S2 terminal on the lighting switch 1 From this potnt a blue cable runs via a snap connector 2 direct to the foot dipper switch 3 The dipper switch is a two way switch From one termina two blue and white cables connect through snap connectors 4 to the main filament in each headlamp bulb 5 From the other termina on the two way switch two blue_and red cables run through snap connectors 6 to the dip filament in each headlamp bulb Here again separate b ack earth cables are fitted to ensure a good return path for the lamps These earth cables connect direct from the bulb holders in the lamp via the control box earth terminal
27. ngements will vary only in detail from the general pattern In the same way satisfactory re wiring operations cannot be covered in any great detail Various methods may be employed which are equally satis factory always providing that adequate stocks of cables and components are at hand Classie Cars S Cycles www lassicCycles org Page 20
28. nt horns such as the windtones to connect them through the ammeter would merely register as a violent and alarming oscillation of the needle when the horn button is closed so a separate fuse is usually supplied with them and the supply taken direct off the hattery line Now examine this picture in detaile Such com ponents as interior lights door lights etc which may be susceptible to wiring troubles will be placed on the A2 fuse cable colour purple Smoall current horns such as the Altette horn may also be connected to this fuse The radio set with its own fuse however can most conveniently be connected from the SA terminal of the control box The supply for the cigar www C lassicC ycles org 12 VOLT BATTERY SD 6 INTERIOR LIGHT HORN PUSH PURPLE amp BLACK ALTETTE HORN lighter and inspection plug sockets may be taken from the battery side of the starter switch as a matter of convenience The supply for heavy duty horns may be taken from this point also or if no ammeter is installed the windtone horn supply may be taken from the A terminal at the control box At least one car maker who does not install an ammeter takes the windtone horn supply from the A2 fuse thus eliminating the additional horn fuse Since there are no other components on this fuse there is no possi bility of putting the interior lights out of action because of a fault on the horn wiring We have covered this i
29. of 012 copper 28 012 with a current carrying capacity of 14 amperes For most purposes this is adequate 3 Side and tail lamp wiring accessory ignition and generator field circuits comprising 14 strands of O12 copper 14 012 with a current carrying capacity of 7 amperes 4 For panel lamp wiring and other incidentals a cable comprising 9 strands of 012 copper 9 012 is the most convenient size It should be realised that this is only a general guide to the cables used in the different circuits New 65 amp 44 012 22 AMPS 28 012 14 AMPS EES 14 012 7 AMPS ZE 9 012 4 AMPS vehicles with Lucas wiring are carefully studied to determine the correct cable sizes Where long lengths of cable are used a larger gauge wire may be necessary to prevent excessive voltage drop For example a vehicle with an exceptionally long cable run for the battery feed six feet or more may be installed with an oversize cable such as 65 012 If at any time this cable has to be renewed a similar size replacement should be installed This last ruling also applies to re wiring on vehicles equipped with the 6 volt system particularly if voltage drop trouble is encountered ee ee EE i Page 7 ClassicC ars amp Cycles EQUIVALENT CABLES CURRENT CARRYING CAPACITY It may be useful to examine how the cable sizes which have been given compare with similar cables identified by other standards of measurement Some
30. ons 2 Cable Clips The essentials here are single and double cable clips 3 Cable Harness Clips and Spring Clips for chassis fixing 4 Cable Eyelets or Terminals 4 and 3 eyelets will cover all requirements 5 Starter Cable Terminals 6 Battery Lugs and Earth Straps This is the simplest form of wiring work WIRING UP ACCESSORY LAMPS OR RENEWING SINGLE CABLES l Always use the recommended size of cable and the correct basic colour which makes for easy identi fication subsequently and also enhances the appearance of the job Take great care to feed the component from the correct fuse or terminal point as we have already detailed 3 Protect the new wire with sleeving where necessary 4 Clip up sufficiently close to prevent sagging in i service which would give a consequent untidy appearance 5 Avoid close proximity to any Hot Spots and any moving parts such as brake cables etc It happens that sometimes a single cable in the harness may require renewal and the obvious way to do this is to run a new cable of the correct size and major colour outside the loom This may be clipped on to the loom at intervals Finally cut off the old cable ends where they enter the harness a PARTIAL REWIRES A typical service rewiring job will be where a section of wiring has become damaged due to a smash or a fire In this circumstance the best and quite adequate method is to cu
31. plicity of models itis not practicable to make them available as spares the delay involved in obtaining a special harness would be completely prohibitive In any of the categories mentioned in order to carry out a good quality job on an economicaLand profitable basis properly organised stocks of cables sleeving jointers clips etc must be available and the range and quantities of these components will vary according to the amount of work anticipated Rev N ewiring In Service WwWw C lassicC ycles org If rewiring work is to be made a speciality a wide range of stock controlled components will be 1equired otherwise the work will quickly become unecono mical as the result of delays and time lost in making up special bits and pieces Within our experience service complaints following re wiring work can be all too frequent and in this section of the course we shall attempt to offer some useful guidance to those undertaking it In every case the fundamentals of a good quality economical job may be assured if 1 The correct size and quality of cable is used 2 Adequate stocks of the basic colours are main tained 3 Suitable stocks of protective sleeving are available 4 A full range of quick jointers junction boxes and other incidentals are at hand Where the work is to be extensive additional facili ties in the way of guillotines wire strippers and other special tools for fitting up will go far
32. t away all the damaged wiring if possible at a common point Then using either a multi point terminal block a junction box or a few snap connectors run new cables of the correct size and basic colour to the various components In many cases it will be possible to re use the old cable run includimgthe rubber grommets clips etc otherwise fit new pieces of insulating sleeving rubber grommets and cable clips as required COMPLETE REWIRES In view of the Jarge amount of labour involved in the re witing of any modern vehicle this job merits careful consideration and a strictly methodical approach Job instructions may only specify a re wire but it is obviously futile to re wire a vehicle to find afterwards that when the vehicle is put back into service the generator doesn t charge or the battery is flat and so on So the very first thing to do is to make a general check over of all the units including the lamps and ascertain that they are in a serviceable condition Proceed as follows Whilst in contact with the customer make a visual check of the following 1 The battery The distributor leads and ignition coil The generator belt commutator brushes bearings The control box condition nw ee UN The starter commutator brushes and bearings Listen to the engagement for undue noise 6 The lighting check the condition and operation where possible Note cracked glasses ill fitting rims etc
33. tem in some detail as a number of exceptions to the standard recommended layout may be found on different vehicles THE RB106 CONTROL UNIT AND FUSE BASE Where the RB 106 control separate fuse base ts used There are two separate current supplies to this base l From the A terminal on the control box a brown 44 012 cable connects to the terminal Al on the base The incidental accessories are con nected at A2 that is through the fuse The supply to the A3 terminal is taken from the ignition switch A3 by means of a white 28 012 cable The ignition accessories fused and un fused will be connected at A4 and A3 res pectively upit is installed a ho Page 17 ClassicC ars amp GENERAL Vehicle re wiring work properly organized is capable of producing a useful revenue as well as providing an essential service facility which no motor engineer can really afford to neglect The work as a whole falls into four different cate gories l Incidental wiring work such as may be involved in the fitting up of accessory lamps and other com ponents 2 Renewing single cables within the wirtng harness or external to it 3 The re wiring of complete sections following damage by collision fire etc 4 Complete rewires involved in major vehicle over hauls In this latter category it is feasible to fit a completely new wiring harness but owing to the multi
34. the undamaged parts of the existing loom f AMM AMM DASH PANEL STOPLIGHT STOPLIGHT SWITCH JUNCTION BOXES AND CABLE CONNECTIONS For general purposes a range of junction boxes and cable connectors is freely available The snap or spring connectors shown greatly facilitate re wiring and general service work They are made in numerous combinations These spring connectors must be borne in mind when fault finding Page 6 TYPES OF CABLE IN USE Now before going into circuits and colour schemes let us examine the types of cables which should be available before embarking on any vehicle wiring repair work They fall into three groups I Starter cables of which there are three sizes STARTER CABLES I The most generally used pattern is a fairly light type of jute covered cable as shown This com prises 37 strands of No 20 SWG tinned copper wire It is suitable for most light vehicle work where the starter motor current does not exceed 400 amperes w Used in conjunction with this is a similar size earth braid which should always be fitted between engine and chassis as a bonding strip when rubber engine mountings are used This standard braid is also suitable for use as the earth lead from the positive terminal of the battery to the earth connection on the scuttle or chassis 3 The two heavier starter cables are of similar con struction to the light one i e j
35. ute covered but have 61 strands of No 20 or 18 SWG and are_used for starter currents up to 700 amps Where this size cable is used for the starter supply further lengths should be made up as a bonding strip and also as the battery earthing lead Classic C ars amp C ycles www C lassicC ycles org 2 Car wiring cables of which there are four popular sizes and as many colours as can be conveniently stocked by the average motor trader 3 Ignition cables which are subdivided into two types a High tension cable i e for spark plugs ete b Low tension cable for primary or low voltage circuits STARTER CABLES Fn re lt a Teen a EE 37 20 SESS SSS SEE lane EARTH BRAID 61 18 amp 61 20 CIRCUIT WIRING CABLES Next we come to the cables necessary for general wiring on the vehicle These are all special cables for the work and com prise a number of copper strands in rubber and fabric sheaths specially treated to be highly resistant to petrol water and oil Such cables are freely available on the market as auto cable There are five sizes of cable altogether in general use on the 12 volt system but for most purposes three are commonly used These are l The battery feed circuit cable comprising 44 strands of 012 copper generally described as 44 012 This cable has a current carrying capacity of approximately 22 amperes 2 Main generator or head lamp circuit cables com prising 28 strands
36. wire switch wire and return remains and it is upon this that the Lucas wiring colour scheme is based Feed wires carry braiding of a main colour only Switch wires have the main colour of feed with a coloured tracer woven spirally into the braiding The return or earthing leads are black THREEWIRES Page 9 ClassicC ars amp Cycles www C lassicC ycles org LUCAS ELECTRICAL EQUIPMENT HOME AND EXPORT MODELS THE STANDARD WIRING DIAGRAM Here we have a typical wiring diagram of which there is one published for most models and makes of vehicles These diagrams are of considerable value in service but a certain amount of difficulty may be experienced by the non specialist in following them out It is however quite simple if each component circuit is considered in dividually which we shall proceed to do commencing with the starter system KEY TO CABLE COLOURS iI wu TEWMITE was PURPLE D TILLOW ehh MAUL lt BR KROLACK 3 PURPLE a WITE 2 BLUE wes n gt SWHUTE ORL DROWN 28 VALOW CaA VATE 4i AEO DE PURILE was GAILN WIRING DIAGRAM 2 BLUE wid YULOW wha SACK DP YELI OW mih GELEN AIRED mih YELLOYY PURPLE eas BAO 4 BLUE wea TE TCRION JI THACW wiih PURPLE CIRIO wrk MUE PLAAT with BLACK E BLUE wud CREON IS OREU atA 800 uy LOW wus BLOWN 46210 u WHITE x BLUE wea Pere TALLOW 1 TILLOW weed BLACK Ok va Geer at to 7 BLUE A BROWN we ia Say PU 1 MOWN ARED td PUAPE MACE war TfL E RUC
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