Found this simple expalanation of the Lucas Wiring Colours :

Lucas Wiring Colours

All Lucas wiring looms have a common colour code, whether the loom is in a Sprite, MG, Mini, Jaguar, Healey, Triumph etc etc. Knowing the code can help a lot, particularly when a manual isn't handy.

Some of the codes are are as follows.

Brown is main power live all the time from the battery, sometimes via the voltage regulator, to the fuse box where it powers all items independent of the ignition system (eg: horn). If you see a heavy brown wire, be careful as it will be live.

Brown with a blue trace is the power feed from the voltage regulator to the light switch (see below - blue = headlights). Brown with a green trace is the power feed from the fuse box to the horn. Brown with any colour trace is likely to be live all the time - be careful.

White is the wire from ignition switch. It will go to the coil and other items that need to be powered by turning on the ignition, such as ignition light and fuse box. The white wires are live only when the ignition is turned on.

Green is power out of the fuse box - the white wire referred to above takes power to the fuse, and the green wire takes power out of the same fuse. So the green wires are also live when the ignition is on, and they are delivering power to various items such as wiper motor, brake light switch, heater switch, fuel gauge, blinker can and tacho. So if your tacho dies and your blinkers don't work, try the wipers. If they don't work either, you just blew the fuse.

One of the above green wires delivers power to the blinker can, and power emerges from the can as green with brown trace and heads to the blinker switch. From there, it heads out as either green with red trace to the left hand blinkers, or green with white trace to the right hand blinkers.

So a plain green wire is powered by the ignition switch (via the fuse box) and green with any colour trace is coming off another switch (heater, brake light, wipers etc etc) or the fuel gauge.

There are so many items powered by green wires that it would be impractical to connect all these wires into the fuse box. As a result, often only one or two green wires come out of the fuse box, but behind the dashboard the bullet ends all get plugged together by one or more of those black rubber joiners. If some of the abovementioned items work and others don't, it's possible that there is a stray green wire behind the dash that hasn't been plugged into it's power supply rubber joiner.

Blue (heavy wire) is the power feed from the headlight switch to the dip switch. From there the power heads out via blue with red trace (low beam) or blue with white trace (high beam and warning light).

Red is always side lights or parking lights. A red wire also goes to the dash light switch, and comes out of the switch as red with white trace. Any red wire with white trace will be a power supply to a gauge.

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David L


My greatest fear in life is that when I die my wife will sell my Mini and tools for the price I told her I paid for them!

Good information that.
I wasn't aware they kept a standard across models. If only other manufacturers used that logic.

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Dean Hutton's first car was a Mini.

Yep as I'v been working on the the vans Loom I have notived you can basicly put it in 4 section Mains (Brown), Ignition (White), Blinkers (Green), Light (Blue) with trace colour to seperate differant area's.

Never considered this was used with Jags, Trumpies etc..but why wouldn't it

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Stop Licking the Dog...I Don't Care Who Started It

Check this http://www.jcna.com/library/tech/tech0014.html
or this http://www.autoelectricsupplies.co.uk/f ... rder_2.pdf

On the same subject, anybody know what the useful life of a Mini wiring loom is, assuming there's never been any shorts, overloading etc?

I have been told copper wiring suffers from oxidation over time, but I must confess I haven't seen any rusty copper-wire lying around lately..............

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1967 Cooper S - new front bearings to do.
1965 Cooper S shell - Slow progress. No time or money!
1966 Deluxe- next rustoration!
Mk 2 & XJ6 Jags. Less said the better.

The copper doesn't lose its ability to carry load, although damage will.

If the ends are made well (crimped and clean), and the loom undamaged (or repaired well) then there is no limit.

There can be problems with inner conductors having cracks when the copper is poor. This won't usually be picked up by a multimeter because it will only cause a problem under high load when the voltage starts dropping across the damage. it will get hot at this point in the loom.

The only way to spot it is to put a full load current through it (maybe 10 amps, a 120watt H4 bulb would provide this for you) measuring the voltage at both ends to see if they reasonably match, and that no hot spots exist in the run (by touch).

Simply however, for the most part the loom carries very small loads. Make sure the connections are clean and tidy, and especially check the headlight runs, the white wires and the brown. these are the high load parts of the loom. Sand the fuse box contacts with a bit of wet and dry and turf the original lucas fuses if you still have them. These are awesome for creating heat, but not so good for voltage drop.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

I love how the lucas colour coding works - saves so many headaches, except when some monkey has mixed them up

I've got a loom out of a triumph that I cut bits out of when I need the right coloured wire

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did I tell you that I won a trophy?

Thanks Mick

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1967 Cooper S - new front bearings to do.
1965 Cooper S shell - Slow progress. No time or money!
1966 Deluxe- next rustoration!
Mk 2 & XJ6 Jags. Less said the better.