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.

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:

• Plain Yellow became Brown with a Yellow stripe, and
• Yellow with a Brown stripe became plain Brown.

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

* 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)

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

Full Colour Code (TC and TD)

* 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

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.

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.

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

MGTF Protective Coverings

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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