Custom Norton Commando Wiring Diagram – Walt (WEM)

Grant Tiller

Walt (username WEM) from the Access Norton Forum has been having a few issues with charging and melting wires on his 1974 Commando.

Originally, Walt’s wiring would have looked like this:

Grant Tiller

A few years ago, he added a Podtronics regulator/rectifier, so the wiring is currently looking like this.

(Note that Walt still has the blue can capacitor on his bike):

Grant Tiller

Walt has recently had some issues with fuses blowing and fuse holders melting.

We have talked him through some tests for the Warning Light Assimilator, Alternator Stator and Reg/Rec and we are seeing some varied results.

Alternator

During the course of this winter, Walt is considering replacing his single phase alternator stator with a three phase one.

The three phase Lucas alternator is a nice choice for superior charging in modern traffic conditions, as you will get a decent output much power down the rev range.

Grant Tiller

Regulator/Rectifier

I have also recommended that Walt considers fitting the superb Shindengen SH775 regulator/rectifier – it will handle his new three phase alternator stator, plus it is a much smarter choice than the legacy Podtronics.

Grant Tiller

This unit’s wiring is identical to the Podtronics it would be replacing, which in turn is a direct replacement for the original Lucas rectifier.

However, I suggest, based on issues experienced up to this point, that Walt considers making a few minor changes as detailed on this page.

The Shindengen is wired in the same way as most aftermarket reg/rec units:

Grant Tiller
Grant Tiller
Grant Tiller

Fuses

Considering the previous issues of fuses blowing and wiring/fuse holders melting, I personally feel it is a good idea for Walt to wire his new reg/rec directly to the battery via it’s own dedicated fuse.

I would recommend using automotive blade type fuses for both this, as well as the original one on the bike.

These are great, as blade fuses are available in every garage, and are very resiliant to vibration.

You can use a 15 amp fuse for both.

Grant Tiller

Charge Warning Light

A worthwhile upgrade is the Charge Warning Light.

The factory warning light assimilator (the Lucas 3AW 3 wire ‘silver can’ assimilator) is very unreliable, and only gives you information that a single phase alternator stator is putting out ‘some’ AC. Not very helpful!

Also, the 3AW can either fail open or fail closed, and can cause major issues with your charging system.

Grant Tiller

The nice thing about the Improving Classic Motorcycles unit that I recommend here is that you can retain the original warning light – so it looks totally factory.

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.

Grant Tiller

Charging System

Here is a diagram that shows the evolution of the charging system on Walt’s bike.

As he is moving from single phase to three phase, I would suggest that he doesn’t try to reuse the GY (green/yellow) and WG (white/green) wires.

We have had issues with these anyway, plus he is moving to three phase, which will require an extra wire.

Note 1: it doesn’t matter which order the yellow AC wires are connected to the reg/rec in.

Note 2: see the extra fuse on the reg/rec black negative wire – this is optional, but I highly recommend it!

Grant Tiller

Capacitor

I have recommended to Walt that he leaves out the blue can capacitor.

From my own testing, I have found a couple of things:

  • The blue can capacitors start to deteriorate significantly after about two years of being on a bike.
  • A lot of Podtronics units I have seen over the last couple of years contain a capacitor in them already (ie I am seeing a charge across the red and black leads after the reg/rec has been removed from the alternator stator and the battery)
  • The new aftermarket ‘Sparx’ branded capacitors are very unreliable – there was even a batch last year that had the positive and negative terminals labelled incorrectly.
  • A good, modern battery does a much better job at smoothing voltage than a capacitor ever could (not the case with the old wet batteries from the 70s)

Of course, there is no issue if you choose to leave the blue can capacitor on your bike.

It’s just my preference to remove them based on my own findings.

So here we go – below you will find a complete wiring diagram for Walt’s bike based on the changes I recommend he implements over the winter.

Custom Norton Commando Wiring Diagram – Walt (WEM) PNG 3066×1841

Grant Tiller

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