Lucas Wiring Colours
Lucas Cable Colours, Sizes and Identification
In the 1950`s the widely used Lucas electrical system layout of wiring cables were standardised for all British made home and export vehicles, this included both cars and commercial vehicles. We hope the information given below will prove useful to the vehicle restorer, (or indeed someone simply trying to trace a fault) to simplify the identification and selection of cables on British manufactured vehicles.
All cables used are of the multiple strand type, this provides flexibility and a much reduced risk of breakage. Each cable is given an identifying symbol which shows the number of individual wires or strands, and the total number of these strands. Therefore a cable conductor comprising 28 strands of copper wire, each a thickness of ·012 inch diameter, or 30 S.W.G is denoted by 28/·012.
The safe current carrying capacities of the 44/·012, 28/·012 and 14/·012 cables are, respectively, 22, 14 and 7 amperes. Note: For long cables giving a definite voltage drop owing to the increased electrical resistance, it is often necessary to use a size larger cable than given above.
The principal of the Lucas colour cable system is that of the feed cable, switch cable and return (earth). Feed cables have outer braiding of one colour only, but all switch cables have the main colour of the feed cable together with a tracer (coloured) woven spirally into the braiding, while return or earth cables are black. When components are switched or controlled on the earthed side, that is, with the switch wire on the return side instead of the feed side, this is indicated by the use of a black tracer.
There are seven main colours, Brown, Yellow, White, Green, Blue, Red and Black, the following are the circuits in which these colours are used:
Brown Cables - For the Battery Circuit. From the battery or starter motor switch to the ammeter or control box, also to a radio set if fitted, from the control (regulator) box terminal A1. Also from the starter motor switch to the electric clock, inspection sockets and battery auxiliary fuse. This usually feeds the electric horn, cigarette lighter, interior lights etc.
Yellow Cables - For the Generator (Dynamo) circuit. From the dynamo terminal D to the corresponding control box terminal and the ignition warning lamp.
White Cables - These are used for the ignition circuit.and other circuits used only whilst the ignition is switched on, but do not require to have fuses, for example, the electric petrol pump, starter motor, solenoid switch etc.
Green Cables - All Auxiliary Circuits which are fed through the ignition system switch but are protected by the ignition auxiliaries fuse, for example, the brake stop lamps, fuel guage, direction indicators, windscreen wipers etc.
Blue Cables - Headlamp Circuits. These are fed from the terminal S2 (or H) on the lighting control switch.
Red Cables - The Side and Tail Lamp Circuits. These are fed from the terminal S1 (or T) on the lighting control switch. Other lamps which are included in this circuit are panel lamps, fog lights and other lamps which are required only when the side (parking) lamps are in use.
Black Cables - Used for the Earth Circuits. Should an electrical component not be earthed internally to the chassis frame a black cable is taken to a good earthing point on the chassis.
© Dugdalevms 2011