Mk 3 wiring

The wiring diagram will have all the correct colours which should tie up with the loom hence connecting up will be straight forward. If you have moved any electrical items or changed any items then there is scope for confusion.
If the ignition system is changed to Electronic (which it should be) then condensers and ballast resistors are no longer needed.
If the Zener diodes are lost or considered unusable then the 'odd' original rectifier fitted to the MKIII and Zeners will be replaced by a regulator/rectifier.
IF the new loom isn't in line with the wiring diagram then of course the new loom is 'not fit for purpose'.

Enter Mk3 final wiring into the search box above.

Regards, Al.

f there is anything non-standard about the electrical set-up, it is very possible that Grant Tiller has a modified wiring diagram for it: https://granttiller.com/

Hi, It is clear from the circuit diagram that the headlight, ignition switch  and warning light cluster do have separate sub looms. 

Hi Dan,

Have a look at (for example) 
https://www.feked.com/genuine-lucas-main-wiring-harness-norton-commando-mk3-06-6396.html?srsltid=AfmBOopPU-xEJZwqWeQgnwnRrlcfb5ataplt7BIaURz38kD1DYOBbR7M
And you will see a picture of the main harness with yellow thread. 
and
https://www.feked.com/genuine-lucas-headlamp-wiring-harness-norton-commando-mk3-1975-06-6438.html
For a picture of the headlamp harness.
The colours of the wires will be as per the circuit diagram.
Other sub harnesses are available but you get the idea.
You should be able to look at wire colours and tie them up with the circuit diagram.
By the way, I have never found anywhere where you can buy the white connectors. Obviously they are available as the looms have them. Anyone know of a supplier?

Firstly ascertain if you have a 3 phase stator? Does it have 9 pole pieces? (6 poles pieces is single phase)
The original MKIII system will have 3 wire connections to the two alternator connections, ie the original rectifier, the two Zeners on the AC side of the rectifier and the 2 to the Ignition Warning Light unit. (4 connections in total)
I suggest these 2 off triple wires are 'removed' or 'made safe' and not used. 
Install 3 off new wires (YLW) from your new stator to the regulator rectifier. And redirect the Ignition Warning Light unit to two of these stator wires. Unless you are cancelling that system and fitting a BSM, which works on the DC side of things.

Att'n Tony Ripley

Tony, are you able to confirm whether these Tricour connectors that Dan mentions are indeed the correct ones? 

Or can anyone else for that matter?  Anyone used them, and are they well made? 

Cheers.

The colours in the handlebar cable are 'standard' meaning as per- WHT is ignition on (via ignition switch) WHT/YLW is ignition on (in this case after ignition kill/cut out switch) WHT/RED is start to solenoid.
Bear in mind this bike is over 50 yrs old, had several owners, and IF wiring has been fiddled with and any rewiring done 'casual' then the results will be 'casual'. Unfortunately the 3 WHT in the one connector are NON STD so we can only guess where they go.

OK, what I am guessing, from what you have and what the circuit diagram shows. 
Is instead of 5 wires coming away, you have a 4 way plus a 2 way.
The two way is for the head / pilot and the 4 way is for cutout and start.
The white wire in the circuit digram is shown as connecting the single power (white) to Cutout and Start internally. But it actually has two separate feeds. So basically just connect the white wires of the 3 core to either of the whites on the 4 core, and it will all work.

Hi Dan.

Not sure if this helps but here is a picture of the five connectors in my headlamp, it's still a standard harness.

Graham

As you have been looking on the most excellent Grant Tiller web site, I presume you found:-
https://granttiller.com/wp-content/uploads/2025/02/1975-Norton-MK3-Commando-Wiring-Schematic-Boyer-ignition-AND-reg_rec.pdf

This should answer all your questions.
Remove the zeners and any associated wiring.
Fit the reg rect wherever is convenient, but unsure somewhere that will get a bit of airflow.
You do not need the amplifier.
You do not need the ballast resistors.
Do NOT use the charge warning light assimilator.

 But also has an original style rectifier and one zener attached to the LHS .........
If this is/was a genuine MKIII then it should have had 2 Zeners (one on each Z Plate) and the 'original style' rectifier would not be a real one but a specific one for the MKIII which is to be removed along with ALL zeners and appropriate wiring (or at least made safe) Now the Boyer Bransden ignition does have an amplifier box, but you do NOT need any ballast resistors (or condensers) all of which should be obvious from the BB fitting instructions. IN effect the regulator/rectifier replaces the original type rectifier. IE there are two stator wires, and then an earth and 'live' to feed the bike and charge the battery ie feeding the BRN/BLU that is the live feed through the bike.

It is possible that the MK3 used 3 different looms, 2 of which we know were used. The plastic Lucas connectors were used by Lucas for around a year or so before being changed by Lucas but the later replacements I have not seen on a MK3. Occasionally boxes of one half of the original MK3 connectors can be found on Ebay as NOS. 
Some over think the wiring, remember at any one time try and deal with a single circuit at anyone time, it only needs a supply and return path, ie 2 cables, or one cable and earth connection. Once the idea of positive earth is understood the rest is just a methodic work through circuit (load) by circuit. if the circuit diagrams online just seem a confusing jumble then get a piece of A4 and draw out each individual circuit.  And of course a digital multimeter or old AVO type devise will help immensely. 

Further to Ashley-Do keep in mind the standard British wiring colours and what the colours mean, ie White (WHT) this is live when the ignition is ON. Brown/Blue (BRN/BLU) is live battery at all times. ETC
If you have power on the bike and searching for a fault where something has stopped, then a 'screwdriver' style tester (with an Earth lead/clip ) is a lot quicker and more reliable than a multimeter. You don't need to know if it is 12.9V or even 11.8V. If lamp is on you have power.

....We now are getting some where, if the stator has 6 poles then it is NOT NOT 3 phase it is an original type RM19 which started life as a 6Volt charging stator and as we all know can be used on 12V. The regulator/rectifier can be any one for Single phase 12V. I sell the A Reg.
The indicator relay is NOT relevant to the reg/rectifier or alternator in any way. Any flasher relay is relevant to the indicators, and the voltage of the system, the original were 2X21W ie 42W and used A Lucas type 2 terminal flasher unit specifically for 2X21W. IF you must use LED indicators you need a specific LED (lower power) flasher unit. As it happens there are many on the market, but beware a lot are for Negative earth only as LED are often specified for Negative earth only. If in doubt get in touch.

Simple solution - buy a new single phase stator as the one you have is not sufficient for a MK3 ES. The Tri Spark MOSFET rectifier will also suit as they are quite efficient when used with a RM23 single phase stator making the need for 3 phase stator on the MK3 pointless. You would need to make / modify the parts to get the modern version of the 3 phase stator to fit a MK3, another reason to keep it simple and and single phase.    

"why would the restorer would have fitted a low output stator?"
'cos that's what he had lying around in a box. I'd be worried about what else he's done...

As for 3-phase versus single phase, since you're replacing all the charging system and rewiring, 3-phase costs the same and is better at re-charging the battery at low revs. Fitting to a Mk3 requires a small adjustment to the stator mounting plate, see Peter Shand's post about 2/5ths the way down here: https://www.nortonownersclub.org/forum/alternator-statorrotor-alignment
Easily done with a file and takes less than 30 minutes (don't modify the stator).

I think the Lucas picture applies to the Canadian spec. which has something to detect whether the headlight is working. Grant's diagram shows 5 connections and is right for the standard Mk3 setup, so tape up the 2 lighting wires and ignore them.