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Thread: Where does this color wire go?

  1. #1
    Join Date
    Nov 2006
    Niagara Falls, Canada

    Default Where does this color wire go?

    While looking at pages of Lucas humor I stumbled upon this list of color coding for wires and thought it might be useful to some.

    From: ( )

    So there you are, grubby Haynes Manual in one hand, circuit tester in the other trying to work out why the lights/horn/wipers/cigarette lighter/clock etc. won't work, (apart from the fact that it has 'Lucas' stamped on it that is.) Tracing the circuit usually works eventually but often you find yourself with several loose wires and no clues as to where they go, in which case you need a clue or two.

    There is a British Standard for vehicle wiring (who said "abysmally low"?) number BS-AU7a which defines the colours and allows you to trace where the wires should go from first principles rather than a diagram. It also allows accessories such as electric fans to be added with the correct coloured wires which assists later diagnosis enormously.

    None of this helps the fact that the things on the ends of the wires are usually made by Lucas too and are therefore of er.. variable quality! I'm particularly fond of a description of an E-type Jaguar's headlamp switch as having" three positions: DIM, FLICKER and OFF.

    Anyway, that's enough potentially libellous comments (I'm sure all Lucas products are simply fab nowadays and the repro stuff is only crap because it is so authentic This info should not only allow you to trace original wires but also to use the correct colours when adding additional equipment like spotlights, ejector seats or whatever.

    Firstly the basics- What The Colours Mean:
    BROWN is for direct, unswitched, unfused supply from the battery. Seen on wires to alternators, dynamos, control boxes and ignition switches etc. Always live and often carrying heavy current.

    YELLOW sometimes used as an alternative to brown on older cars. Also used on solenoids and overdrive switches.

    PURPLE Direct, unswitched but fused supply from the battery. On older cars with no purple wires, brown wires with a secondary tracer colour are used.

    WHITE Unfused supply from the ignition switch.

    GREEN Fused supply switched via the ignition switch. Used for things like the wiper motor, indicators and brake lights which only work when the ignition is on.

    BLUE The main colour for front lights- headlamps and spotlamps.

    RED The main colour for rear and side lights.

    BLACK Usual colour for wires from components to earth points on the body.

    These refer to the main colour of the wire. The second tracer colour which is on many wires is the thinner line and is used to identify the wire. There is a certain amount of logic to them too as you will see.

    Below is the colour code table for BS-AU7a which was amended in the 'eighties so there will be a few variations on our '50s to '70s cars..

    Main colour is given first , tracer second

    Black All earth connections
    Black/ Brown Tachometer generator to tachometer
    Black/ Blue Tachometer generator to tachometer
    Black/ Red Electric or electronic speedometer to sensor
    Black/ Purple Temperature switch to warning light
    Black/ Green Relay to radiator fan motor
    Black/ Light Green Vacuum brake switch or brake differential pressure valve to warning light and/or buzzer
    Black/ White Brake fluid level warning light to switch and handbrake switch, or radio to speakers
    Black/ Yellow Electric speedometer
    Black/ Orange Radiator fan motor to thermal switch

    Blue Lighting switch (head) to dip switch
    Blue/ Brown Headlamp relay to headlamp fuse
    Blue/ Red Dip switch to headlamp dip beam fuse. Fuse to right-hand dip headlamp
    Blue/ Light green Headlamp wiper motor to headlamp wash pump motor
    Blue/ White a) Dip switch to headlamp main beam fuse
    b) Headlamp flasher to main beam fuse
    c) Dip switch main beam warning light
    d) Dip switch to long-range driving light switch
    Blue/ Yellow Long-range driving light switch to lamp
    Blue/ Black Fuse to right-hand main headlamp
    Blue/ Pink Fuse to left-hand dip headlamp
    Blue/ Slate Headlamp main beam fuse to left-hand headlamp or inboard headlamps when independently fused
    Blue/ Orange Fuse to right-hand dip headlamp

    Brown Main battery lead
    Brown/ Blue Control box (compensated voltage control only) to ignition switch and lighting switch (feed)
    Brown/ Red Compression ignition starting aid to switch. Main battery feed to double pole ignition switch
    Brown/ Purple Alternator regulator feed
    Brown/ Green Dynamo 'F' to control box 'F' Alternator field 'F' to control box 'F'
    Brown/ White Ammeter to control box. Ammeter to main alternator terminal
    Brown/ Yellow Alternator to 'no charge' warning light
    Brown/ Black Alternator battery sensing lead
    Brown/ Slate Starter relay contact to starter solenoid
    Brown/ Orange Fuel shut-off (diesel stop)

    Green Accessories fused via ignition switch
    Green/Brown Switch to reverse lamp
    Green/ Blue Water temperature gauge to temperature unit
    Green/ Red Direction indicator switch to left-hand flasher lamps

    Green/ Purple Stop lamp switch to stop lamps, or stop lamp switch to lamp failure unit

    Green/ Light green Hazard flasher unit to hazard pilot lamp or lamp failure unit to stop lamp bulbs
    Green/ White Direction indicator switch to right hand flasher lamps
    Green/ Yellow Heater motor to switch single speed (or to 'slow' on two- or three-speed motor)
    Green/ Black Fuel gauge to fuel tank unit or changeover switch or voltage stabilizer to tank units
    Green/ Pink Fuse to flasher unit
    Green/ Slate a) Heater motor to switch ('fast' on two- or three-speed motor)
    b) Coolant level unit to warning light
    Green/ Orange Low fuel level switch to warning light
    Light green Instrument voltage stabilizer to instruments
    Light green/ Brown Flasher switch to flasher unit
    Light green/ Blue a) Flasher switch to left-hand flasher warning light
    b) Coolant level sensor to control unit
    c) Test switch to coolant level control unit

    Light green/ Red Fuel tank changeover switch to right-hand tank unit or
    entry and exit door closed switch to door actuator
    Light green/ Purple Flasher unit to flasher warning light

    Light green/ Green Start inhibitor relay to change speed switch; or switch
    to heater blower motor second speed on three-speed unit
    Light green/ White Low air pressure switch to buzzer and warning light
    Flasher switch to right-hand warning light; or
    Light green/ Yellow differential lock switch to differential lock warning light
    Light green /Black Front screen jet switch to screen jet motor

    Light green /Slate Fuel tank changeover switch to left-hand tank unit; or entry and exit door open switch to door actuator

    Light green/ Orange Rear window wash switch to wash pump; or cab lock-down switch to warning light

    Orange Wiper circuits fused via ignition switch
    Orange/ Blue Switch to front screen wiper motor first speed timer or intermittent unit
    Orange/ Green Switch to front screen wiper motor second speed
    Orange/ Black Switch to front screen wiper motor parking circuit, timer or intermittent unit
    Orange/ Purple Timer or intermittent unit to motor parking circuit
    Orange/ White Timer or intermittent unit to motor parking circuit
    Orange/ Yellow Switch to headlamp or rear window wiper motor feed, timer or relay coil
    Orange/Light green Switch to headlamp or rear window wiper motor parking circuit timer or relay coil
    Orange/ Pink Timer or relay to headlamp or rear window wiper motor feed
    Orange/ Slate Timer or relay to headlamp or rear window wiper motor parking circuit

    Purple Accessories fed direct from battery via fuse
    Purple/ Brown Horn fuse to horn relay when horn is fused separately
    Purple/ Blue Fuse to heated rear window relay or switch and warning light
    Purple/ Red Switches to map light, under bonnet light, glove box light and boot lamp when fed direct from battery fuse
    Purple/ Green Fuse to hazard flasher
    Purple/ Light green Fuse to relay for screen demist
    Purple/ White Interior lights to switch (subsidiary circuit door safety lights to switch)
    Purple/ Yellow Horn to horn relay
    Purple/ Black Horn to horn relay to horn push
    Purple/ Pink Rear heated window to switch or relay
    Purple/ Slate Aerial lift motor to switch up
    Purple/ Orange Aerial lift motor to switch down

  2. #2
    Join Date
    Nov 2006
    Niagara Falls, Canada

    Default continued

    Red Main feed to all circuits mastered by sidelamp switch
    Red/ Brown Rear fog guard switch to lamps
    Red/ Blue Front fog lamp fuse to fog lamp switch
    Red/ Purple Switches to map light, under bonnet light, glove box light and boot lamp when sidelamp circuit fed
    Red/ Green Bulb failure unit to right-hand-side and rear lamps
    Red/ White a) Sidelamp fuse to right-hand side and rear lamps
    b) Sidelamp fuse to panel light rheostat
    c) Fuse to panel light switch or rheostat
    d) Fuse to fibre optic source
    Red / Yellow Fog lamp switch to fog lamp or front fog fuse to fog lamps
    Red/ Black Left-hand, sidelamp fuse to side and tail lamps and number plate illumination
    Red/ Pink Sidelamp fuse to lighting relay
    Red/ Slate Lamp failure unit to left-hand side and tail lamps
    Red/ Orange Fusebox to rear fog guard switch
    Red/ Slate Window lift main lead

    White Ignition switch or starter solenoid to ballast resistor

    White/ Brown Oil pressure switch to warning light or gauge, or starter relay to oil pressure switch. Choke switch to choke solenoid (unfused) and/or choke to
    White/ Blue switch to warning light, or electronic ignition distributor to drive resistor. Starter switch to starter solenoid or inhibitor switch
    White/ Red or starter relay or ignition (start position) to bulb failure unit
    White/ Purple Fuel pump no 1 or right-hand to changeover switch
    White/ Green Fuel pump no 2 or left-hand to changeover switch. Start switch to starter interlock or oil pressure switch
    White/ Light green to fuel pump or start inhibitor switch to starter relay or solenoid
    White/ Yellow Ballast resistor to coil or starter solenoid to coil. Ignition coil contact breaker to distributor contact
    White/ Black breaker, or distributor side of coil to voltage impulse tachometer
    White/ Pink Ignition switch to radio fuse
    White/ Slate Current tachometer to ignition coil
    White/ Orange Hazard warning lead to switch
    White/Yellow a) Overdrive
    b) Petrol injection
    c) Door locks
    d) Gear selector switch to start

    PINK WIRE(!)
    Pink/ white Ballast terminal to ignition distributor

    That's all folks! The usual disclaimer applies., ie that This is correct to the best of my knowledge but you use this information at your own risk. So don't sue me if you blow your alternator or fry all your relays...

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