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The MG TD/TF Wiring Looms

These pages contain detailed information about the wiring looms used in the MGTD and MGTF. The first section, from Barrie Jones, contains information about the wiring color codes used inside the harnesses. The second section, from Bruce Sharman of Bygone Spares and Restorations, describes the loom outer coverings or sheath in great detail. The last section deals with battery cables with information provided by Rob Grantham, Australia.

The MG Wiring Colour Code

A guide to the wiring colour codes of the MG sports car by Barrie Jones. © 2009 by Barrie Jones

The automotive wiring colour code that we know today was invented around 1936. I believe the company that invented and maintained it was Ripaults, not Lucas. Ripaults Cables Ltd is a long-established manufacturer of automotive cable and wiring looms in the UK.

The Ripaults colour code quickly became the de facto standard in the UK. Each colour was denoted by a unique letter, and some letters were reserved for other purposes. MG did follow the colour code, but unfortunately they did not use the letters on their wiring diagrams until 1962, staying with an earlier system where the wiring diagram used numbers and a cross-reference table was required.

Different codes were followed in other countries, and many cars sold in the UK used the German code, particularly VW. Ford cars could have either UK or German looms, depending on where they were built.

Reserved letters
A = Ammeter
D = Dynamo
E = Earth
F = Field coils
L = Light or Lights (as in head light, and also light green!)

Colours
B = Black
R = Red
O = Orange
W = White
N = browN
U = blUe
G = Green
P = Purple
Y = Yellow

The only significant change to the colour code was around 1955, when the primary colour Yellow was changed to Brown. Secondary colours were not changed at that time, so Yellow with a Red stripe became Brown with a Red stripe, etc. The special cases were:

MG continued to use Yellow on the TF and all the MGAs, only changing to Brown when they introduced the MGB in 1962.

At some time, the primary colour of Purple was introduced for those wires that were fused (A1-A2) and permanently live (e.g. the horn circuit). The timing of this change is unclear, because some TDs used the new colour code, although the TF and the MGA did not.

Since then, new colours have been added to the system, notably Light Green (LG), Slate grey (S), Pink (K) and Orange (O). There is one light green wire in the TF loom. I assume that Ripaults chose S for Slate grey because they had already used G, R, E and Y.

The first table (following) shows the meaning of the primary colour. For example, all white wires are part of the ignition circuit, they are not fused, and they are switched via the ignition switch

Primary Colour Code

Primary Colour Code Use Fused Switched
White W A3 - Ignition & Fuel pump no Ignition
Black B Earth no no
Brown N Charging circuit no no
Yellow Y Charging circuit no no
Blue U Headlights no Headlight switch
Red R Sidelights no Sidelight switch
Green G A4 - brake lights, wiper motor & heater A3-A4 Ignition
Purple P A2 - horns & courtesy lights A1-A2 no

* some brown wires are fused prior to the introduction of purple

The second table (following) shows most of the wires in the TF loom, including those with a stripe. For example, the wire between the distributor and the coil should be white with a black stripe, coded WB.

Full Colour Code (TF)

Primary Colour Colour Code Lucas Lettering Use
Black B E Earth
Brown N   Battery to ammeter
      Battery to fuse box A1
  NU A1 Light switch to regulator A1
  NW A Ammeter to regulator A
  NG A2 Fuse box A2 to horns
  NB   Horns to horn button
Yellow Y Dynamo D to regulator D
Ignition warning light to regulator D
  YG  Dynamo F to regulator F
Blue B S2 Light switch to dip switch
  BW   Dip switch to headlamp main beam
      Dip switch to headlamp warning light
  BR   Dip switch to headlamp dipped beam
Red R S1 Light switch to sidelights
      Light switch to number plate light
      Light switch to panel light switch
      Light switch to fog light switch
  RW   Panel light switch to panel lights
White W A3 Ignition switch to coil SW
      Ignition switch to fuse box A3
      Ignition switch to ignition warning light
  WP *   Rear Nearside turn indicator & brake light
  WN *   Rear Offside turn indicator & brake light
  WB CB Coil to distributor contact breaker
Green G A4 Fuse box A4 to turn indicator switch
      Fuse box A4 to turn indicator relay
      Fuse box A4 to wiper motor switch
      Fuse box A4 to petrol warning light
      Fuse box A4 to accessories (e g heater)
      Fuse box A4 to brake light switch
  GP   Brake light switch to turn indicator relay
  GB   Petrol tank sender to petrol warning light
  GR   Front Nearside turn indicator
  GW   Front Offside turn indicator

* I know they are white, but logically they should have been green

Full Colour Code (TC and TD)

Primary Colour Colour Code Lucas Lettering Use
Black B E Earth
Brown N Battery to ammeter
    A1 Battery to separate fuse box A1
  NU A1 Light switch to regulator A1
  NW A Ammeter to regulator A
  NG * A2 Fuse box A2 to horns
NB *   Horns to horn button
Yellow Y D Dynamo D to regulator D
Ignition warning light to regulator D
  YG F Dynamo F to regulator F
Blue B S2 Light switch to dip switch
  BW   Dip switch to headlamp main beam
Dip switch to headlamp warning light
  BR   Dip switch to headlamp dipped beam
Red R S1 Light switch to sidelights
      Light switch to number plate light
      Light switch to panel light switch
      Light switch to fog light switch
  RW   Panel light switch to panel lights
White W A3 Ignition switch to coil SW
      Ignition switch to fuse box A3
      Ignition switch to ignition warning light
  WB CB Coil to distributor contact breaker
Green G A4 Fuse box A4 to turn indicator switch
      Fuse box A4 to turn indicator relay
      Fuse box A4 to wiper motor switch
      Fuse box A4 to petrol warning light
      Fuse box A4 to accessories (e g heater)
      Fuse box A4 to brake light switch
  GP   Brake light switch to brake lights
  GB   Petrol tank sender to petrol warning light
  GR   Front nearside turn indicator
  GW   Front offside turn indicator
Purple * P A2 Fuse box A2 to horns
  PB   Horns to horn button

* Some TD looms used purple, most used brown

The Wiring Harness Coverings

This section is a compilation of information and comments to me from Bruce Sharman of Bygone Spares and Restorations in Western Australia, which manufactures custom harnesses to your car specifically. © 2013 by Bruce Sharman

I have original samples of wiring harnesses in my “museum” for want of a better description. It appears from our samples and research that Vic Longden carried out that most Lucas harnesses started out black. As an electrical change was made in the circuitry, then a coloured trace was added to the outer braid. When another change occurred another trace was added. We believe that this aided the car manufacturer (for example MG) identify the harnesses and ensure they were fitted correctly to the correct model. This was not necessarily at “official” model change, but could occur midway through a production run or could be for changes in the circuitry for export models.

I have most of the colours from M types through to the last of the MGBs. This can be quite complicated as some of the cars with several components to the harness, could have different colours in each part of the harness, depending if a change occurred to that particular section. Also as already mentioned the colours change midway through a production run of a particular model, so a lot of my information also relates back to a chassis number rather than model type. Then to add to this complication during the fifties some cars had a combination of Khaki and black. Our theory is this may have been due to cotton or dye shortages post war. Then throw into this mix the fact that the earlier cars (up to late 40s ish) are braided with 4 strand thick cotton as opposed to the later cars which have 6 strand cotton braiding.

A few words about the direction of the tracer and braiding

It is all based on the braiding machine. This machine has 24 bobbins. 12 with cotton running to the RH side of the braid and 12 running to the LH side of the braid. It works like a maypole, with the bobbins going around and under over each other, just like dancers round a maypole. If I am using this / symbol it means the trace is running to the RH side of the braid, ( so looking from above this dancer is running clockwise (CW), when using this \ the trace is running to the LH side of braid and the dancer would be running anti clockwise (ACW). When using this X symbol there is one dancer running CW and one running ACW When using this //\ symbol there are 2 dancer next to each other running CW and one running ACW When using / black / black /. There are 3 dancers running CW with a black dancer in between each.

The norm then is to run the braid from each sub branch end to the main branch (using a tree as an analogy). Once this is completed then run the braid down each main branch to the trunk. Once all are completed then we start at the thickest end (usually dash end) and braid down the main trunk. Sorry if this is confusing, but it is the only way I can explain the direction the trace runs down the harness without seeing the machine in operation. Again distance between traces varies because of the machine. If there are only a few wires, distance is generally about ¾". Where there is a big thick bunch of wires, i.e. bulkhead area it can increase to about 1" spacing.

Short video of Bruce's braiding machine in action.

MGTD Harnesses

The following tables describes the harness during the production of the MGTD.

On the MGTD harness all are six strand, both body and tracers. All TD harnesses were black. At one time it was thought that some TD's had brown looms but it is now believed the dies were variable and the brown harnesses were just faded black harnesses.

Car Number Range Harness Type Drive Tracer Colour Direction Comment
0251 - 8141 with RF95 regulator Main Right Yellow /  
8142 - 19299 with RB106 regulator Main Right Yellow / At one time thought to be a white tracer but now believed to be yellow
9300 to end Main Right Yellow /  
0251 - 8141 with RF95 regulator Main Left Yellow X Crossed yellow trace tracer
8142 - 19299 Main Left Yellow //\  
19300 to end Main Left Yellow //  
0251 - 19299 Tail Both Yellow /  
19300 - end Tail Both Yellow \ Trace now goes in opposite direction
0251 -18882 Panel Both Red / Single ½ red trace
18883 - end Panel Both Red X Single ½ red trace

Panel harnesses are 6 strand black and 3 strand red.

This is for the main harness no details for the tail so I assume it is the same as RH drive cars.

MGTF Harnesses

The following table describes the harness during the production of the MGTF. All looms are 6 strand cotton.

Car Number Range Harness Type Drive Colours Direction Comment
TF501- TF1509 with toolbox pump Main  

orange, black, 3 brown, 2 black, 2 brown, black, 2 brown in this order

Then going in the opposite direction

3 black, 4 brown, 3 black, 2 brown, in this order

\

 

 

 

/

This gives a total of 24 cottons of 6 strand each so as with all harnesses they have to be made on a 24 bobbin machine. Some are made on 16 and less bobbin machines and are not correct
TF1510 - end with wheel arch pump Main   orange, black, black, brown with the rest of bobbins being black ////  
Chassis TF501 - end Panel   orange / single tracer
Chassis TF501 - end Headlamp and Parking Lamp   orange / single tracer

Protective Tubing for MGTD and MGTF Wiring

Various wires on the MGTD/TF harnesses received special protective coverings beyond the loom braiding. These were either from a wear perspective or to keep the environment or automotive fluids from damaging the wires and causing shorts. Many of these covers would need to be applied before the wiring connectors are added, especially in the case of the larger round connectors. Where available you can select the hyperlink on the location text to see an picture of the protective covering.

Not all cars had all of this protective tubing. I will use the ± character to indicate an item that may or may not have been in place for your car.

MGTD Protective Coverings

Location Material Dimensions Comment
Over the coil to distributor white/black wire.± Rubber 3/16" x 9" On NA cars we see rubber on the ends of the cable (~1")
Over the fog light wire Rubber 3/16" x 23" The fog lamp wire was terminated with a single bullet connector
Over the number plate wires Rubber 3/8" x12" Some cars have a 9mm PVC cover instead of rubber
Over brown wire at the starter switch/solenoid on earlier cars Rubber 1/4" x 6"  
Later cars had a cover over the 2 brown wires at the starter switch/solenoid PVC 9mm x 8"  
Over LH rear± PVC 12mm x 24"  
Over RH rear± PVC 12mm x 24"  
Over each park light cable± PVC 4mm x 13" If indicator cabling is included all these will need increasing in diameter
Over beginning of tail branch± PVC 12mm x 8"  

MGTF Protective Coverings

Location Material Dimensions Comment
Below regulator past fuse PVC 18mm x 2"  
Over regulator PVC 16mm x 2 ½"  
Past relay to fuse PVC 16mm x 2 ½"  
Coil to Relay PVC 12mm x 2 ½"  
Horns PVC 14mm x 35"  
Horns PVC 12mm x 17"  
Over Left Hand Rear PVC 12mm x 24"  
Over Right Hand Rear PVC 12mm x 20"  
Number Plate Cable± PVC 10mm x 18"  
Over coil to distributor white black± Rubber 3/16" x 7" On NA cars we see rubber on the ends of the cable (~1")
Right headlamp wire near fuel line connector PVC 14mm x 3"  
Over each park light cable± PVC 10mm x 15" Note on picture spiral protector is not original

MGTD and MGTF Batter Cables

The following images are new old stock (NOS) MGTD/TF battery cables with their original packaging.

Above battery cable photo's courtesy of Rob Grantham, Australia.

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