Wiring Colour Codes for 29 Junior

[Mike57]

I have just removed all the wiring from my 29 Junior. Every wire was black and not routed the correct way. Does anyone have the wiring colour codes for a 1929 Junior please. I am pretty sure they were not all black. I don't intend to use cloth covered cables (not during this mini tidy up anyway) but I would like to see if I can get the colours close to what they should be. I will make up the loom myself.

I have found the British pre-war colour standard but it is not much help.

[jeans_old_man]

Can't help with the Junior but here is the wiring diagram for the 1934 Sports. Notice the note at the bottom that states that the colours refer to coloured sleeves on the ends of the leads - so the wires might well have all been black! Brian

[mothy]

Thus may be of interest.
Lucas Standard Wiring Colours.

I know it mentions radio and indicators but the system was certainly evolved in the 1930s if not before.

Roly

————-

Brown means live all the time (=connected to the battery post)

White means brown that has come through the ignition switch and can therefore be switched off with a key (coil, fuel pump)

Green is white that has gone through a fuse in the fusebox and is therefore (like wipers) switchable and fused

Purple is brown that is fused and therefore permanently live (horn and interior lights plus radio)

Blue is lights. Power comes from the brown to the switch so that lights can be switched on whilst the ignition is off. [Note. sidelights (red) are fused but headlights are not.]
The supply from the headlamp switch is blue as far as the dip switch where it goes to blue/red for dipped and blue white for high-beam. From the switch it is red/green until it reaches the fusebox where it becomes red only. The panel lamps are red into the switch (comes on when the sidelights come on) and become red/white as they travel to the individual bulbs

white/black is from coil to dizzy plus to RVC type distributor.

Black is earth.

green/red is right indicator
blue/white is left indicator
green/black is fuel tank sender
green/purple is brake lights (therefore fused and comes on after the ignition is live)



--
Roly Alcock - 07730557952

[casadecabra]

Interesting that none of the wiring diagrams of the period include the petrol pump, presumably because it was of non Lucas/Rotax manufacture. Worth bearing in mind if you are thinking of ordering a harness.

[mothy]

Morris 8 wiring diagram shows the electric pump. Feed wire is white which matches the description I posted earlier.

Roly

[ColinB]

Unfortunately the Junior wiring diagram doesn't show wire colours. My car came with some original wiring which was encased in a metal sheath. I have replicated this as you can buy a similar product. The wire colours are modern but I am happy with the overall look which is similar to the original. I need a few more clips but the wiring is pretty stable in its sheath.

[Mike57]

Thanks for the replies. I do have the colour scheme for the 34 Le Mans but things had progresses a fair way betwéen 29 and 34. The explanation from Mothy is very useful so I will probably follow that general scheme.

I was not aware that the wiring was originally in a metal sheath Colin so I might look for something like that.

On a related question I was going to use 4mm2 wire for most of the circuits. Maybe the side lights could be something smaller and the horn. What size cable have others used for 6 volt systems.

[ColinB]

Here is another picture of the main original wiring in the containment under the fuel tank. Again you can see the metal sheathing.

[ColinB]

I use the fattest core I can manage for 6v. Vintage Car Parts do the sheathed cable in the UK.

[jeans_old_man]

'Thin-wall' insulated wire is the cable of choice because it is rated to 105 degC and being thin lets the heat out of the copper. 2.0mm2 is rated to 25A. The heaviest load in a Junior is probably the headlights at 12A the pair.

The other consideration is the voltage drop in 6V circuits. A two metre circuit would have a resistance of 0.0185 ohms and therefore a pair of 36W headlights taking 12A would suffer a voltage drop of 12 x 0.0185 = 0.22 volts - a good argument for using LED headlight bulbs.

If you use that dreadful wire with an extra woven jacket you will need to derate to 4mm2 and very soon you will have a harness that looks like a tree trunk!

As coloured PVC was not available in 1929, I suspect the wiring was covered in black rubber and I will be interested to hear from Colin what was on his Junior.

Brian

[david.bryant]

What remnants of wire I have on the junior appears to be cotton insulated possibly then painted. Many places the wires are bare and the cotton drops off when flexed.
regards
David

[Phillip]

I believe the construction of the wiring would have been a stranded copper core with a rubber insulation, covered with a lacquered woven cotton cover, which provided the colour coding. The major sections were bundled together in another layer of braided cotton, usually black with a tracer colour. This was certainly the practice from the early thirties, but I suspect the 1920's was a bit different. There certainly seems to be less bundling of the loom and more of the armoured cable mentioned.

I think the 'Prince of Darkness' reputation that Lucas gained in later years has more to do with the design of the wiring loom, as the rubber insulation breaks down and the cotton braiding holds water and rots. Eventually you have bare copper wires touching each other and ...poof..the Lucas smoke escapes!

The modern 'period' replacement loom, like those made by Autosparks, use a plastic insulation and rayon braiding.

[Mike57]

When calculating the cable sizes do not forget the derating for temperature and bundling. For example a 4.5mm2 cable if running though the engine bay where you might get 70 degrees C temperature and in a bundle of 5 cables has a rating of 11 amps whereas a single cable at 30 degrees has a rating of 48 amps so dont forget that apart from the voltage drop the derating especially in the engine bay needs to be considered.

[jeans_old_man]

Yes, but let's not get carried away. The only high-current circuits are the charging circuit - 12A (say), the headlights - 12A and the flashers (if fitted) - 7A. I would not recommend running the dynamo continuously at 12A. If it has a fixed output use LED headlight bulbs and turn the output down to something like 6A.

The armoured cable from vintage car parts is rated at 16A and 27A.

Brian

[Mike57]

Here are the cable de-rating factors for Tycab cables (an Australian manufacturer) just for interest.