Triumph TR3 drawing


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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.

TR3 fuel sender  resistance specs:  70 ohms full, 0 ohms empty

Source for coded wires, wire harnesses, connectors and tools in the US: British Wiring


All ground connections

Black/ Green

Relay to radiator fan motor


Headlamp connections


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


Main feed from the battery. No switches or fuses


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)


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


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


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


Ignition circuit, no additional switches, not fused


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


Generator connections wired through the ignition switch

Yellow/ Green

Dynamo 'F' to controlbox 'F' Alternator field 'F' to control box 'F'

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