Norton Commando Wiring Diagrams
This article went out in the July copy (issue 391) of the Norton Owners Club magazine – Roadholder
I like to help people with electrical and wiring issues on their bikes, and often frequent the superb Access Norton Forum as well as the various Facebook Groups.
Several times, I have run into issues with trying to get the message across with people that find working with electrics and electronics scary and daunting and have resorting to scribbling on the original wiring diagrams that can be found in the workshop manuals.
However, these diagrams are of course in black and white, so I started looking for a decent colour one that I could refer to.
I ran into a diagram made by Bill Turnbull back in January 2013 and with Bill’s kind permission I subsequently tweaked, edited and added to it.
Bill’s Diagram covers the 1972 onwards Commando (the one with four wires going to the ignition switch)
I took this as my template, and corrected a couple of the factory errors:
- indicator switch wires (GR and GW) should be terminated at the main connector block
- the factory drawing did not show BW and BY wires at the points
- correction to the colour of the wire going between coil and ballast resistor (should be WP)
- there was an error on Bill’s original diagram where the pin numbers (3 and 4) were accidentally swapped around
This new and improved version was well received across social media, and importantly it made my life easier when trying to assist people with their issues.
Subsequently, I made several different versions of this diagram covering some of the popular upgrades and modifications – Boyer Bransden electronic ignition, Tri-Spark electronic ignition, Podtronics combined regulator/rectifier are two typical examples.
Again, these went down a storm!
Toward the end of 2019 I added two other Commando models to the collection:
- Pre-1971 – the bikes with an ammeter in the headlight shell and the Wipac Triconsul type handlebar switch
- 1971 – this has three wires going to the ignition switch, instead of four as implemented the following year and thereafter.
In addition, I added further upgrades and modifications as people requested them – covering things like – Colorado Norton Works electric start conversion, Power Arc electronic ignition, and Electrex World CDI ignition and alternator replacement (I have also blogged about by personal experience with this kit)
Once again, positive feedback from peers on the Forums!
However, the elephant in the room, and the single biggest topic of feedback was:
“Yeah, thanks for that, but where’s the MK3”
So, in January I started work on putting together a new, colour wiring diagram for the MK3.
I didn’t like the one in the back of the workshop manual, and when sat side-by-side with the others, I found the layout confusing and not at all logical.
So, I started again.
I laid out all the components (battery, lamps, alternator, rectifier etc…) on the page in the same places as on the pre-MK3 diagrams.
Then I set about wiring it all up in a layout that was easy to read and understand.
After a few re-visits and major adjustments, I settled on something I was happy with.
Once again, I corrected a couple of the factory errors:
- Corrected the wire colours used on the warning lamps (console sub-harness)
- Added an extra blue/white wire for the main beam flasher on the left handlebar switch (which was not shown correctly originally)
- Added a grey wire for the starter button on the right handlebar switch (not shown at all on the factory drawing)
- Removed the additional earth at the battery – in May 1975 (the NVT days), there was an urgent service bulletin sent out to Triumph dealers instructing them to cut out the small gauge red wire between battery and frame on the T160, leaving only the heavy gauge cable that went to the engine case next to the starter motor). This was because with the heavy cable removed, if you accidentally pressed the starter button, it was possible to melt the wiring loom. The same issue existed on the MK3 Commando, although an official service bulletin was never sent out.
Just to confuse us all, there are actually three different types of MK3 Commando wiring configurations out there:
- 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.
- 1975 MK3 this is the most common configuration, and takes us through to the final Commando that rolls off the production line.
- 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.
So, the MK3 wiring diagrams took me the best part of a month to complete, before ‘grafting in’ all the various upgrades like – Boyer Bransden electronic ignition, Tri-Spark electronic ignition, Podtronics combined regulator/rectifier etc…
So there you have it – my gift to the Norton Commando Community, and hopefully a legacy that will long outlive me!
I have included two diagrams in this article:
Which are probably the two most popular of the six covered.
I would like to thank Les (also known as L.A.B on the Access Norton Forum) as he spent a lot of time looking at my diagrams, checking my work, suggesting some of the edits, and highlighting some of the factory errors that needed addressing.
Please feel free to visit my website www.granttiller.com where you can search, browse and help yourself to the full selection of wiring diagrams (there are around one hundred diagrams up there now)
I have also made several ‘custom’ diagrams for people that may be running something a little different or out of the ordinary (Sparx, Lucas RITA etc…).
If you have something that’s not detailed on my site, contact me through the site, the Access Norton Forum or via the usual Facebook groups and tell me what you need – I may be able to help.
All of the diagrams on the site are the same size, and look great when printed out in A3 – they are something you can laminate and keep in the workshop.
Well done Grant . A legacy indeed
Thank you Ian!
If I’ve helped just one person get a bike back on the road, it’s all been worthwhile!
Hi Grant, I am currently in the process of a ground up restoration of my 1971 Norton Commando Long Range Fastback. The project is now fairly well on and I am about to start on the electrics.
I have been looking at the various custom wiring diagrams that you have produced, pretty amazing stuff.
I came across the wiring diagram that you produced for Grant Hepburn which is very similar to what I propose to do with my own bike. I plan to utilise the following:
Remove factory 6 volt ignition coils and replace with cNw 12 volt dual output single ignition coil.
Remove factory points, condenser & ballast resistor and replace with Tri-Spark electronic ignition.
Remove factory single phase alternator stator and replace with 3 phase Lucas alternator stator.
Remove factory capacitor, zener diode & rectifier and replace with solid state reg/rec wired directly to battery.
Remove factory warning light assimilator and replace with “Improved Classic Motorcycle Charge Warning Light”.
Install a solid state “3 pin” flasher module with warning light driven by the 3rd pin on the flasher module(LED turn signals).
I intend to stay with the Positive Earth system.
I intend to utilise a Shorai LFX21A6-BS12 lithium battery.
I have a question regarding the choice of solid state reg/rec. I have narrowed it down to the Shindengen SH775 (utilised by Grant Hepburn), the Tri-Spark-Spark solid state mosfet reg/rec or Rex’s Speed Shop “Lithium Battery Mosfet Reg/Rec.
Do you have any experience or feedback on the above reg/rec, particularly with the use of a Lithium battery, I have read that cNw utilise the Tri-Spark-Spark unit with this battery.
In addition my wiring harness will be subtly different from the Grant Hepburns wiring diagram in that my early model still utilises the “Two Position Light Switch” but does utilise the later “Four Position Master Switch”
Have you a wiring diagram similar to Grant’s but incorporating the “Two Position Light Switch”.
Many thanks for any advise or assistance that you can provide with my project.
I have tried emailing you about this a few times as I would love to help you.
However, no reply yet.
If you can drop me a line, I would be pleased to assist!
I am pleased to give you a link to the wiring diagram I have put together for your bike:
Hopefully I have captured everything.
Don’t hesitate to reach out if there is anything else I can do to help.
Hi bill, darroll munson, I am rebuilding a 73 850. I’m down to wiring everything thing up. I bought a service manual but it seams like the three options don’t match my bike. I want to try and stay original but is there a simpler way to wire it. I have two b/y& two w/b to one coil then two w/p & two b/w to the other. One w/p goes back to the back fender area? To complicated. Thanks
Hi Darroll, this is not Bill’s site but perhaps I can assist.
There should be two cables that come up from your points plate:
BW (black/white) – looking at the points plate this is usually the front contact breaker and services the right cylinder
BY (black yellow) – looking at the points plate this is usually the back contact breaker and services the left cylinder
Originally these cables went to the condensers.
From the condensers, the same BW and BY cables went on to the coils positive terminals.
There is a link wire between the two coil negative terminals which is WP (white/purple) – it goes to the ballast resistor.
I hope that helps.