*** Updated for February 2025 ***
I first published this page in 7th July 2019.
My new schematics have been drawn from scratch and I have included:
- better resolution – they can be printed on A2 paper (23.4in x 16.5in) without any loss of quality.
- sized for UK and Europe – originally the page was sized for US Legal (14in x 8.5in) paper, and resizing for A4/A3/A2 standard didn’t work.
- cable colours were confusing – it was difficult to see what was the dominant colour ‘vs’ what was the trace colour.
- for MK3 move the key switch from the right to the left side of the page.
- show the warning lamp colours.
- lighter background – ideally there would be no background, but as there are a lot of white cables this would make it difficult to read. I have lightened up the background, and outlined the white cables, it works much better for printing now.
- make points/condenser arrangement clearer.
- show terminals on turn signal flasher unit.
- group additional fuses on early MK3 schematic.
- improved labelling.
There are numerous other small improvements too, which make the schematics easier to read.
This page covers the two most popular aftermarket upgrades seen on our Norton Commandos.
- PODtronics regulator/rectifier
- Boyer Bransden Micro MKIII or Micro MKIV electronic ignition.
Regulator/Rectifier
One of the most common upgrades or modifications for a classic british bike is to add a combined regulator/rectifier unit.
Our Commandos use a blue can capacitor, zener diode (which can be found mounted on the back of the z-plate) and rectifier unit.
A combined regulator/rectifier replaces all of these components with one package.
The most common manufacturer of these is PODtronics.
There are four wires to connect:
| Wire Colour | Description |
|---|---|
| Yellow (x 2) | these are the AC input and pick up on the Green/Yellow and White/Green (connection can be any way round, as this is the AC side of the circuit) |
| Red | this is the Positive output and will join to the red wire if you are using existing wiring (it goes straight to the ground/earth of the frame) |
| Black | this is the Negative output (known as the hot wire) – it will pick up on the Brown/Blue wire (which goes via a fuse straight to the battery negative terminal) |
Warning Light Assimilator
The factory warning light assimilator is not compatible with most modern regulator/rectifiers and the PODtronics is no exception so it has been removed from the schematics.
Plus, there is the matter of what the WLA is actually doing, and how much use that is.
The WLA is looking purely for some AC output from the alternator stator (about 6 ½ volts AC) it is not designed for a three phase stator either.
It gives you no information about the charging (i.e., the regulator (zeners) and rectifier)
It gives you no information about the state of the battery.
Charge Warning Light
I have taken the liberty of adding an ICM Charge Warning Light to the schematics – I can certainly recommend the Improving Classic Motorcycles charge warning light as a brilliant alternative.
I use them myself, and have had a good experience with them.
The nice thing about the Improving Classic Motorcycles unit is that you can retain the original warning light – so it looks totally factory (this for me is an important factor with the MK3 with it’s quirky little instrument panel).
It gives you a lot more useful information about the state of the battery and charging system compared to the standard assimilator unit, which looks for AC output from the alternator stator only.
Electronic Ignition
Another really popular Norton Commando upgrade is to move from the old points-based ignition system over to Electronic Ignition.
One of the most common units of the time is Boyer Bransden, who have been around since 1969.
They are still going today, and their website can be found here.
Moving from points to Boyer electronic ignition is a pretty simple upgrade.
From a wiring perspective, the most important thing to note is that you will be moving from a pair of coils that are wired in parallel to series.
Originally, the points make and break the positive (earth) side of each coil in turn.
The Boyer electronic ignition system uses a concept called “wasted spark” – with the two coils wired in series, they are energized together on every rotation of the camshaft.
You’ll note in the wiring diagrams below that the Ballast Resistor and Condensers have been removed as part of the conversion to Electronic Ignition.
The color coding of the wiring make connecting this up nice and simple:
| Wire Colour | Description |
|---|---|
| Red | This is the positive feed to the Boyer, and is usually picked up from the red wire that goes to the Coil positive terminal |
| Black | This is the negative supply FROM the Boyer TO the coils |
| White | This is the negative feed to the Boyer. It joins in to the White/Blue wire that used to feed the Ballast Resistor that you are removing. As standard, this goes up to the big connector block under the tank, where it’s joined to the White/Yellow that is the kill switch on your left side handlebar switch cluster |
| Black/Yellow Black/White | these go from the Boyer black box (they call it the Transistor Box) down to the Stator Plate that sits behind the points cover |
Note – the wiring is the same for both the Boyer Bransden Micro MKIII and Micro MKIV systems.
1968 Norton Commando Wiring Schematic + Boyer Bransden ignition AND PODtronics reg/rec
These are the pre-1971 bikes and have the ammeter in the headlight shell, as well as the Wipac Triconsul type handlebar switch.
The wiring is very simple, and more like the Atlas than what came to be familiar with the Commando.
Note that I have included the Front Brake Switch as standard – this was a US requirement, that didn’t appear on the earliest UK bikes.
1968 Norton Commando Wiring Schematic + Boyer Bransden ignition AND PODtronics reg/rec PNG 5600×3960
This diagram is also downloadable as a PDF from HERE
1971 Norton Commando Wiring Schematic + Boyer Bransden ignition AND PODtronics reg/rec
This is often referred to as the “Interim” model.
It is distinguishable by the three pin master switch (ignition key switch) which was Lucas part number LU39565.
These were made ONLY for the Norton Commando, and are no available as an aftermarket replacement.
If you are not comfortable rebuilding the switch, most people choose to go for the LU30552, which IS readily available.
You can find an article on ignition switches here, that may be of interest.
1971 Norton Commando Wiring Schematic + Boyer Bransden ignition AND PODtronics reg/rec PNG 5600×3960
This diagram is also downloadable as a PDF from HERE
1972 onwards Norton Commando Wiring Schematic + Boyer Bransden ignition AND PODtronics reg/rec
The 1972 onwards schematic covers 750 and 850 bikes and has the much more familiar four pin master switch (ignition key switch)
1972 onwards Norton Commando Wiring Schematic + Boyer Bransden ignition AND PODtronics reg/rec PNG 5600×3960
This diagram is also downloadable as a PDF from HERE
MK3 Commando
During the manufacture of the MK3, Norton and Triumph were coming together, and they were often feeding from the same parts bins.
We have noted some anomalies between the handlebar switches while the MK3 was in production, as they frequently used the Triumph T140E switches, which look the same, but have a couple of small wiring differences.
Left handlebar switch the U (blue) used by Norton (and illustrated in the factory workshop manual) has been replaced with a UY (blue/yellow) cable. This connects to the U (blue) of the right handlebar switch inside the headlamp bucket.
Right handlebar switch there is no S (slate grey) instead, the single “hot” negative from the pin 2 of the Master Switch (ignition key switch) is jumpered for both engine run/kill switch and the starter button.
Another element of the MK3 that sometimes causes confusion is the wiring around the Warning lights.
The factory workshop manual shows the following:
I have covered this in more detail in a separate article, which can be found here.
But in short, the cable colors used for the sub-console wiring harness were not the same all the way through MK3 production – so certainly something to watch out for!
1974 Norton MK3 Commando (Early) Wiring Schematic + Boyer Bransden ignition AND PODtronics reg/rec
1974 MK3 Early Bikes – there were around 2,000 bikes that were built around the December 1974 timeframe that have three additional fuses that can be found in the headlamp bucket.
1974 Norton MK3 Commando (Early) Wiring Schematic + Boyer Bransden ignition AND PODtronics reg/rec PNG 5600×3960
This diagram is also downloadable as a PDF from HERE
1975 Norton MK3 Commando Wiring Schematic + Boyer Bransden ignition AND PODtronics reg/rec
This is the most common configuration, and takes us through to the final Commando that rolls off the production line.
1975 Norton MK3 Commando Wiring Schematic + Boyer Bransden ignition AND PODtronics reg/rec PNG 5600×3960
This diagram is also downloadable as a PDF from HERE
1975 Norton MK3 Commando (Canadian Market) Wiring Schematic + Boyer Bransden ignition AND PODtronics reg/rec
For the Canadian Market, there were legal requirements around the headlamp being on while the engine was running.
A different Master Switch (ignition key switch) is fitted in order to adhere to law in Canada. More info is available here in a separate article.
This is covered in the Factory Wiring Diagram, by notes.
The Canadian key switch LU30825 is not available, and must be rebuilt manually.
1975 Norton MK3 Commando (Canadian Market) Wiring Schematic + Boyer Bransden ignition AND PODtronics reg/rec PNG 5600×3960
This diagram is also downloadable as a PDF from HERE
NOTE:
A couple of points about the way these diagrams have been drawn:
- The diagrams on my site are schematics – the components are not drawn in the physical location on the bike. Instead they are drawn in locations that make the diagram the easiest and most logical to follow.
- Where the same colour wire goes in to and out of a single connector, that connector has usually been omitted from the drawing.
It’s obvious on the bike, is easy to spot and easy to troubleshoot.
Leaving them off the diagrams makes them a LOT easier to read, and considerably less cluttered. - Wherever the earth or ground side of a component goes back to the battery, the drawing shows a red earth symbol:
In reality, this could be connected either to a red wire in the bike’s wiring harness (loom) OR it could be attached to the frame or engine of the bike.
I have shown the red earth symbol each time in order to massively simplify the diagram, and make it a lot easier to understand for everyone.
I have also coloured them red as a gentle reminder that these bikes are wired positive earth!
This diagram includes BOTH the Boyer Electronic Ignition AND the Podtronics combined Regulator/Rectifier unit.
Pre-1971 (ammeter in the headlight shell and Wipac Tricon type handlebar switch) PNG 3066×1841
1971 (three wires to the master switch) PNG 3066×1841
1972 onwards (four wires to the master switch) PNG 3066×1841
1974 MK3 Early Bikes – there were around 2,000 bikes that were built around the December 1974 timeframe that have three additional fuses that can be found in the headlamp bucket.
These bikes are also wired with the old Lucas 3AW 3 wire ‘silver can’ assimilator.
1974 MK3 (Early) PNG 3066×1841
1975 MK3 this is the most common configuration, and takes us through to the final Commando that rolls off the production line.
1975 MK3 (Original) PNG 3066×1841
1975 MK3 Canadian Market – there were legal requirement in Canada around the headlamp being on while the engine was running, so the wiring diagram includes changes needed (swapping out the Warning Light Assimilator 06-6393 for the Headlamp Warning Unit 06-6392). Note that a different Master Switch is also required.
This is covered in the Factory Wiring Diagram, by notes.
1975 MK3 (Canadian Market) PNG 3066×1841
The Boyer and Podtronics pairing is probably the most common set of upgrades to a bike.
NOTE:
A couple of points about the way these diagrams have been drawn:
- Where the same colour wire goes in to and out of a single connector, that connector has usually been omitted from the drawing.
It’s obvious on the bike, is easy to spot and easy to troubleshoot.
Leaving them off the diagrams makes them a LOT easier to read, and considerably less cluttered. - Wherever the earth or ground side of a component goes back to the battery, the drawing shows a red earth symbol:
In reality, this could be connected either to a red wire in the bike’s wiring harness (loom) OR it could be attached to the frame or engine of the bike.
I have shown the red earth symbol each time in order to massively simplify the diagram, and make it a lot easier to understand for everyone.
I have also coloured them red as a gentle reminder that these bikes are wired positive earth!
Warning Light Assimilators
It is important to note that MOST aftermarket reg/rec manufacturers do not support either the pre-MK3 Lucas 3AW silver can warning light assimilator OR the MK3 one.
Boyer Bransden are very explicit in their instructions for the Power Bow – they have even made an alternative Power Box model that includes a charge warning light.
Other manufacturers (PODtronics, SPARX and the Tri-Spark MOSFET units) either mention it in their smallprint/FAQs or neglect to mention it at all.
As such, I would recommend NOT using the original assimilator and consider your alternatives.
You could replace your assimilator with a solid state equivalent like the CoolCat Express (warning: you have to buy positive SS3AW-P or negative SS3AW earth)
Alternatively, you could follow my recommendation and buy a Charge Warning Light instead.
A warning light assimilator tells you that the alternator stator is producing an AC output, whereas a Charge Warning Light tells you that the battery is charging, the reg/rec is working and it gives you much more useful information about performance of the charging system and the state of charge.
I personally recommend the Improving Classic Motorcycles “Standard” Charge Warning Light. This model wires in to the standard incandescent lamp, so it looks better than a modern LED. It matches all your other warning lamps, which is particularly important on the MK3 with it’s instrument ‘console’
The ‘brainbox’ is about the size of a postage stamp, and can easily live inside the headlight bucket or under the MK3 ‘console’
Categories: Aftermarket Upgrades, motorcycles