Lucas wiring colour code for Triumph

This table provides the standard Lucas wire colour codes used in Triumph TR3s. I have added the Lucas codes for accessories that might be added to a TR3, such as driving lamps, radio and electric fan.

This table is the work of TeriAnn Wakemen


Black - All ground connections

Black/Green - Relay to radiator fan motor


Blue - Headlamp connections

Blue - Headlamp switch to dimmer switch

Blue/White - Headlight high beams

Blue/White - High beam dimmer switch to indicator lamp

Blue/White - Dimmer switch to long-range driving light switch

Blue/Red - Headlight low beams


Brown - Main feed from the battery. No switches or fuses

Brown/Yellow - GEN to volt. regulator

Brown/Blue - Power feed to headlamp switch

Brown/White - Ammeter to main alternator terminal

Brown/Yellow - Long-range driving light switch to lamp

Brown/Yellow - Alternator to 'no charge' warning light

Brown/Purple - Alternator regulator feed

Brown/Green - Fuse to horn (No relay)

Brown/Black - Horn to horn button (no relay)


Green - Ignition circuit, additional switches or fused

Green/Black - Fuel gauge to fuel tank unit

Green/Blue - Water temperature gauge to temperature sender unit

Green/Red - Direction indicator switch to left-hand flasher lamps

Green/Purple - Stop lamp switch to stop lamps

Green/White - Direction indicator switch to right hand flasher lamps

Green/Yellow - Heater switch to heater motor


Light green/Blue - Flasher switch to left-hand flasher warning light

Light green/Brown - Flasher switch to flasher unit

Light green/Purple - Flasher unit to flasher warning light


Purple - Accessories fed direct from battery via fuse

Purple/Brown - Horn fuse to horn relay when horn is fused separately

Purple/Red - Switches to map light, under bonnet light, glove box light and boot lamp when fed direct from battery fuse


Red - Tail lights, instrument lights and side markers

Red/Yellow - Fog light switch to fog light or fog light fuse to fog lights

Red/Blue - Front fog light fuse to fog light switch

Red/White - Fuse to instrument lamp switch, Instrument panel lamps


White - Ignition circuit, no additional switches, not fused

White - Power to coil

White/Black - Ignition coil to distributor

White/Brown - Oil pressure switch to warning light

White/Pink - Ignition switch to radio fuse

White/Red - Ignition switch or starter switch to starter solenoid


Yellow - Generator connections wired through the ignition switch

Yellow/Green - Dynamo 'F' to control box 'F' Alternator field 'F' to control box