'73 OEM Wiring diagram question

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MexicoMike

MexicoMike

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I've looked in my (hard copy) Norton service manual, my (hard copy) Haynes manual, searched on line and have had no luck with this:

I cannot find a diagram showing the wiring for the OEM ignition condenser (capacitor) pack on the '73 Commando. In fact, none of the wiring diagrams depict the ignition capacitor(s) at all - as far as the specific wiring colors from the harness.

Anyone have a wiring diagram that DOES depict the entire OEM ignition system, INCLUDING the capacitor pack in relation to the wiring harness/colors?
 
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MexicoMike said:
I cannot find a diagram showing the wiring for the OEM ignition condenser (capacitor) pack on the '73 Commando. In fact, none of the wiring diagrams depict the ignition capacitor(s) at all - as far as the specific wiring colors from the harness.
Click to expand...

'73 OEM Wiring diagram question
 
Thanks Lab. I should have been more clear. I realize that the caps are depicted as per an electronic schematic in all the diagrams I have seen but I'm looking for the wiring convention in relation to the wiring harness - what color wires go where.
 
MexicoMike said:
AH...I think I found what I need. :) I guess I should have kept the instructions from when I bought the new harness back in 2006! I screen-shot/saved this for my Norton files:
Click to expand...

That diagram has some errors.

The original harness 'ballast resistor to (both) coil(-)' was white/purple (WP) not WY.
The three wires marked "Blue lamp flasher unit" are the assimilator wires!
The two wires marked "Warning Light Assimilator" are the auxiliary power socket wires.
The rear indicator wires are also marked incorrectly as green/white is RH and green/red is LH.

Therefore, in the area close to the coils, the harness should contain a black/white (BW) and a black/yellow (BY) with spade connectors which connect to the condenser tags and also a red with a spade connector that attaches to the condenser pack earth tag.
 
Hmm...My Lucas replacement harness circa 2006 has is no white/purple wire anywhere. I'm trying to mentally "reverse engineer" what I did when I installed the TriSpark and in doing some circuit checking, it SEEMS that the ignition portion of the diagram in question agrees with my harness. Don't know about the other items. Sadly, although I usually make thorough notes of anything I've done, I didn't think to make a diagram of how it was connected when I was running the OEM setup. But since I bought that Lucas harness and connected it without any issues that I remember, whatever instructions it came with were fine. I don't remember if it came with that diagram or had some specific step-by-step instructions.

"Why am I doing this?" I hear some folks asking... Well, I have often said that if anything went wrong with the TS I would just go back permanently to the OEM points/AAU. So I'm thinking of doing just that - going back to OEM and seeing if I WOULD be happy with the OEM system or if I'm just running my mouth! ;) We've got a ride on Thursday - around 200 miles so if I'm going to make the change I should get to work! :)
 
L.A.B. said:
Yes, the 'Lucas' harness has WY wires as shown on their diagram.
Click to expand...

It didn't occur to me that the OEM harness and the Lucas harness were different. I ASSUMED that Lucas made the OEM harness and therefore a Lucas harness would be identical to the OEM! You know what they say about assumptions! ;)
 
MexicoMike said:
It didn't occur to me that the OEM harness and the Lucas harness were different. I ASSUMED that Lucas made the OEM harness and therefore a Lucas harness would be identical to the OEM! You know what they say about assumptions! ;)
Click to expand...

Indeed, as the 'Classic Lucas' trademark is licensed to W E Wassell.

https://www.totalbikebits.com/wassell_history.html
"In 2014, Wassell acquired the licence for the Lucas brand from Lucas Industries Limited, for Classic Motorcycle parts. In conjunction with Lucas, an extensive product development programme for Classic Motorcycle parts was initiated, to once again, establish Lucas as a market leader within the industry."

(According to information on another forum the Classic Lucas harnesses are made in the UK by Autosparks)
 
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I have 2 wire color coded schematics for ‘71-74 which depict the harness white/blue passing through the ballast resister, terminating at the negative of coil #1. From there it shows black wire from negative of coil #1 to negative of coil #2. And then + Of each coil to a condenser and then from condenser to ground.
It appears that this black wire is not part of the loom.
 
lazyeye6 said:
I have 2 wire color coded schematics for ‘71-74 which depict the harness white/blue passing through the ballast resister, terminating at the negative of coil #1. From there it shows black wire from negative of coil #1 to negative of coil #2.
Click to expand...

The ballast to coils wire (both as it doesn't terminate at coil1 (or coil2) but continues to coil 2 (or coil1) so one terminal has two+ WP wires) should be marked WP (white/purple). Although not marked on the 71-74 diagrams the 850 Mk3 diagram this wire is marked 'WP'.

850 Mk3
'73 OEM Wiring diagram question



lazyeye6 said:
And then + Of each coil to a condenser and then from condenser to ground.
It appears that this black wire is not part of the loom.
Click to expand...

The points/condenser/coil wires as mentioned are BW and BY. The condenser section is included in the harness but the points wiring is a separate section.
https://andover-norton.co.uk/en/shop-details/17657
 
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Also:
An original harness can have a WP and a white/red WR extending to the battery compartment which would have been electric starter solenoid connections IF they'd got around to fitting an electric starter before the Mk3.
Those two wires are not shown on the 71-74 diagrams and along with the extra Interpol wires they do not appear to be included in the latest harnesses.
The horn also has a separate 'link lead' extension.
https://andover-norton.co.uk/en/shop-details/15761
 
Any idea why some wires in the harness are double same-color wires with single terminal? Doesn't make any sense to me. If the idea of a double wire is to carry more current, then the return wires have to be the same capability...but they are not. For example, a double black/yellow and a double black/white goes to each coil + terminal. But only a single wire from the - terminal. I don't get it. :(
 
MexicoMike said:
Any idea why some wires in the harness are double same-color wires with single terminal? Doesn't make any sense to me. If the idea of a double wire is to carry more current, then the return wires have to be the same capability...but they are not. For example, a double black/yellow and a double black/white goes to each coil + terminal. But only a single wire from the - terminal. I don't get it. :(
Click to expand...

Whenever you see a double wire on a terminal, it simply is a branch to go to another individual electrical component. For instance the double black/yellow wire that attaches to the spark coil has one wire that goes to the points while the other wire goes to the capacitor.

There are no internal wire splices within the wiring harness. Whenever you see a double wire on a terminal it acts as an external splice. So not only should terminals be clean and tight on the electrical component, the wire crimp should be secure as well otherwise you may have a problem with another electrical component downstream which could be difficult to troubleshoot.

Peter Joe
 
I've spent two days futzing with wiring in my temporary (?) conversion back to points/AAU and was much confused for a bit over the difference between the wiring harness colors in the Lucas harness and the various wiring diagrams. I forgot whatever I learned back when I installed the harness and didn't make any notes so it was all "new" to me.

I have several different diagrams for my year bike, including the one in the Norton hard copy service manual and three from the internet, including one in color. In the ignition area they are all different. None of them match the Lucas harness in that regard. Further the directions for connecting the Lucas harness are also incorrect!

So I'm doing what I should have done back when I installed the new harness originally in 07 or thereabouts - marking up a diagram to match MY bike.

I definitely recommend that if you do any electrical work - whether changing something or just doing some routine checking/maintenance on the wiring - you compare your wiring with a wiring diagram and, if necessary, make the appropriate notations. For example, one critical wire on my Lucas harness is the one going to the ballast resistor. Per the Lucas instructions, it's a blu/white wire. It's also blu/white on ONE of the wiring diagrams, white/yellow on another, and white/purple on yet another. But none of those wires is the correct wire on my harness, "Lucas Part Number 54960724 Norton Commando 1970-74 Main Harness." The white wire is correct. NONE of the wiring diagrams show a white wire as being correct. But if you back-trace that ballast resistor wire on the Norton Service manual diagram, you will see that it starts life as a white wire at the ignition switch. In the Lucas harness it remains a white wire BUT the instructions don't show that. If you use the blue/white wire, per the lucas (and one of the wiring diagrams) the ignition will not work.
 
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MexicoMike said:
For example, one critical wire on my Lucas harness is the one going to the ballast resistor. Per the Lucas instructions, it's a blu/white wire. It's also blu/white on ONE of the wiring diagrams, white/yellow on another, and white/purple on yet another.
Click to expand...

Without knowing exactly which diagrams you are referring to it's difficult to say, but the 71-73 (there is no 74 diagram) factory diagrams all show blue/white (UW) from the main junction to the ballast resistor which is correct.



MexicoMike said:
But none of those wires is the correct wire on my harness, "Lucas Part Numbest 54960724 Norton Commando 1970-74 Main Harness."
Click to expand...

The only incorrect colour ignition circuit wire on the Lucas diagram is the white/yellow ballast to Ignition coil (1&2) wiring which was white/purple originally but not marked as such on the 71-73 factory diagrams.

'73 OEM Wiring diagram question



MexicoMike said:
The white wire is correct. NONE of the wiring diagrams show a white wire as being correct. But if you back-trace that ballast resistor wire on the Norton Service manual diagram, you will see that it starts life as a white wire at the ignition switch.
Click to expand...

I don't understand what you mean? Correct for what? For the ignition circuit, white (W) runs from teminal 2 of the ignition switch to the main junction point (shown on the Lucas diagram as "Headlamp Loom Connection"). From there, it goes to the kill switch through the switch cluster harness section as W and from the kill switch as white/yellow WY and connects to white/blue WU at the main junction.


MexicoMike said:
But if you back-trace that ballast resistor wire on the Norton Service manual diagram, you will see that it starts life as a white wire at the ignition switch.
Click to expand...

Yes. Edit: White (W) from the ignition switch goes to a double-common as W also feeds other circuits.
'73 OEM Wiring diagram question



MexicoMike said:
In the Lucas harness it remains a white wire BUT the instructions don't show that. If you use the blue/white wire, per the lucas (and one of the wiring diagrams) the ignition will not work.
Click to expand...

But, what the Lucas diagram doesn't show are the handlebar switch cluster sections, one of which includes the kill switch wiring as they're not part of the main harness.
 
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"I don't understand what you mean? Correct for what?"

Sorry, I wrote very unclearly. What I meant was that the white wire from the ignition switch is the original "source" of the power to the ballast resistor (and other components). The diagrams I have been referring to are that Lucas harness picture, the Shop manual, and two additional diagrams from the internet, one labeled '74 Commando and the Old Britts diagram of the ignition system.

But I think I have it all sorted out now. Part of the source of my confusion was my own fault that I just realized today...years ago I disconnected the kill switch so there is no power available at the blue/white wire. The lack of power there was what started my entire "confusion issue. As I said earlier, back then I didn't make any notes of what I did. I won't make that mistake again! :)

Thanks LAB!
 
MexicoMike said:
But I think I have it all sorted out now. Part of the source of my confusion was my own fault that I just realized today...years ago I disconnected the kill switch so there is no power available at the blue/white wire. The lack of power there was what started my entire "confusion issue.
Click to expand...


Yes, without the kill switch then WU needs to be connected to W for power to reach the ballast resistor, coils, etc.
 
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