Norton Commando Wiring Diagram + Tri-Spark + cNw + Podtronics

Grant Tiller

As promised, below you will find the wiring diagrams which have been modified to include Tri-Spark electronic ignition, the Podtronics regulator/rectifier and the Colorado Norton Works Electric Start Conversion.

Pre-1971 (ammeter in the headlight shell and Wipac Tricon type handlebar switch) PNG 3066×1841

Grant Tiller

1971 (three wires to the master switch) PNG 3066×1841

Grant Tiller

1972 onwards (four wires to the master switch) PNG 3066×1841

Grant Tiller

Very popular modifications giving you a bike that is suitable for modern day motorcycling!


A couple of points about the way these diagrams have been drawn:

  1. 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.
  2. Wherever the earth or ground side of a component goes back to the battery, the drawing shows a red earth symbol:
    Grant Tiller
    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’

5 replies

  1. Grant, what program are you using to do these? I’m specifically interested in the ability to get the two colors on the wires. Thanks, David

  2. Hi Grant,

    Further to my recent last email – apologies. I found the wiring diagrams after I sent the email!

    Just a quick question.

    Do I need to fit a ‘noise filter (?)’ to the system to prevent misfiring problems with the Trispark system or just use a different rec/reg to the Podtronics.


    • Hi Dave – great to see you have found the cNw wiring diagrams.

      If you have anything different to what I have listed here, don’t hesitate to reach out.

      If your Podtronics and Tri-Spark combo are fitted and are not showing any issues, then you are good to leave everything exactly as it is.

      The issue does not seem to manifest on all Podtronics units, just a few of them.

  3. Thanks Grant, your reply is appreciated.

    I haven’t purchased any components yet and might just get the new stator and MOSFET kit from TriSpark when I get the new ignition system. I imagine I would then just substitute out the Podtronics reg/rec in the diagram.


    • David,

      I really like the Shindengen open-type reg/rec.

      I use them myself, recommend them to others, and have never seen one go bad.

      There are a lot of counterfeit units on the market, so be careful.
      Maybe order one from Jack at Roadster Cycle (, and get him to ship it to Matt Rambow at Colorado Norton Works, to include in the box to you in Australia.

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