wiring loom question esp: horn connection/ whats what

L.A.B. said:

There are a few errors on that diagram.
The one below is accurate.

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I did lift the diagram posted from this site but maybe before it was updated?

I now understand how I developed all those new words during the rewiring phase of my restoration.

Good to know from here on.

@L.A.B. I don't know if this is right, but it looks like there isn't much that is correct about the wassell wiring?

gforce said:

@L.A.B. I don't know if this is right, but it looks like there isn't much that is correct about the wassell wiring?

Grant Tiller | Lucas/Wassell 1970-74 Norton Commando Headlamp Harness

Wassell make a great wiring loom for the Norton Commando. Specifically I am referring to this sub-harness Lucas Part Number 54960724 which is listed as being for the Norton Commando 1970-74 Headlamp Harness. Wassell sell this item under the Lucas name, as they have licensed the rights to use the...

granttiller.com

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It's the Trust Lucas diagrams that seem to be at fault more than the actual harnesses themselves so the factory diagram should also be used.

L.A.B. said:

I know you have the Wassell 'Lucas' main harness section but do you also have a new Wassell Lucas headlamp harness section or are you going to use the original Lucas?
Also, is the master switch an original Lucas and does it have 3 or 4 terminals, or is it a modern replacement switch?

As I mentioned previously, there was a change made to the harness in early '72 when the 3-terminal master switch was replaced with the 4-terminal switch (both 4-key position) and an additional separate UY headlamp feed from the 4th master switch terminal to the headlamp switch, therefore, if the headlamp harness is the later original Lucas or Wassell Lucas then one of the headlamp switch wires will be UY.
Because you will be using the direction indicator/blinker toggle as a substitute headlamp dip switch (High-Low beam) then the other switch wire is LG/N from the switch cluster, Edit: which will need an extension wire so connect LG/N to headlamp harness U or, the headlamp switch could simply be bypassed by connecting LG/N from the switch cluster to the main harness UY.


If, however, the headlamp harness section you intend to use is the 'early' original Lucas and/or it has the Lucas 3-terminal switch or modern replacement switch then call back.

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Hey there LAB. So, I finished wiring up the bike yesterday. There were a few leads that I did not end up using because I couldn't find matches on the loom, headlight harness, or components on the bike. I also did not connect the kill switch. I couldn't sort that out in terms of connecting the ballast resistor correctly. I'm struggling with that and will give it some time until I can get my head around it. As it sits right now, the wiring is correct with the ballast and coils to get the bike running. Once I figure out the kill switch wiring I can update later. For now, I can just turn the key off to stop the motor, or as I normally do on my 850, is just turn off the fuel valve and let it starve - this way I remember to open it next time I go for a ride.

Just a reminder. I have a '72 Combat (confirmed with the C stamped on the head, and the sound of it running). I purchased a new original Lucas set of main harness loom (part# WW19082 54960723), and headlamp harness (Part# ww19106C 54960724). This headlight harness has that extra UY wire that you mentioned. Both came in the large red box and stated for models 1970-1974. I have a 3-terminal ignition switch that appears to the be original. I have no indicator lights on the front or the back. I just have the rear and brake lights on the rear, and the headlight on the front.

So, I am planning on connecting the battery today and see how things work. I'll check the lights. I'll also turn the ignition on and turn over the engine and see if I get a spark at the plugs with them laying on the head. This should tell me that all is ok with my wiring. Am I missing anything you think? I'm not thinking there's much chance of me messing up the wiring on this machine. All leads are connected to their correct polarity. Thoughts?

Bye the way, thank you for these diagrams!

Cheers,
Rob

Starvingphotog said:

There were a few leads that I did not end up using because I couldn't find matches on the loom, headlight harness, or components on the bike. I also did not connect the kill switch. I couldn't sort that out in terms of connecting the ballast resistor correctly.

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I assume you have connected W to WU, to bypass the kill switch.

To include the kill switch, connect the switch cluster WY (kill switch wire) to the WU wire at the "Headlamp Loom Connections" position on the diagram (and connect the WU and WY wires marked "Ballast Resistor" to the ballast resistor).

Starvingphotog said:

I purchased a new original Lucas set of main harness loom (part# WW19082 54960723), and headlamp harness (Part# ww19106C 54960724). This headlight harness has that extra UY wire that you mentioned. Both came in the large red box and stated for models 1970-1974. I have a 3-terminal ignition switch that appears to the be original.

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As they both have the UY wire then they are actually the later '72-'74 harnesses intended for use with the 4-terminal master switch although can be used for all '71-'74 models (not '70 - '74 that's another error!) as there's no '71- early '72 version, therefore, the master switch UY must be connected to terminal 3 with the NG wire (or three-terminal switch replaced with a four-terminal switch).

As you probably know by now the three wires marked "Blue Lamp Flasher Unit" (WN, GY & R) are the assimilator wires and the two marked "Warning Light Assimilator" (NU & R) are the Auxilliary Power Point wires.

L.A.B. said:

I assume you have connected W to WU, to bypass the kill switch.

To include the kill switch, connect the switch cluster WY (kill switch wire) to the WU wire at the "Headlamp Loom Connections" position on the diagram (and connect the WU and WY wires marked "Ballast Resistor" to the ballast resistor).



As they both have the UY wire then they are actually the later '72-'74 harnesses intended for use with the 4-terminal master switch although can be used for all '71-'74 models (not '70 - '74 that's another error!) as there's no '71- early '72 version, therefore, the master switch UY must be connected to terminal 3 with the NG wire (or three-terminal switch replaced with a four-terminal switch).

As you probably know by now the three wires marked "Blue Lamp Flasher Unit" (WN, GY & R) are the assimilator wires and the two marked "Warning Light Assimilator" (NU & R) are the Auxilliary Power Point wires.

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Ok LAB. I think this is it! I connected the kill switch like you instructed. I also added the UY wire to the terminal 3 on the ignition switch. And, yes, I found out about the switch on the main harness for the Blue Lamp Flasher Unit for the Warning Light Assimilator, and the residual Auxilliary Power Point two wire pair. So, we are good there.

I think I'm ready to attach power and see what happens! Wish me luck!

Cheers,
Rob

Starvingphotog said:

I think I'm ready to attach power and see what happens! Wish me luck!

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Good luck (but keep a fire extinguisher handy!)

Its called smoke testing for a reason ;-)

haa haa! You guys are great!
Well, no smoke. No fire. I got a spark on each plug when I turned the engine over. My warning light assimilator works when I turn the key. The kill switch works when I press it and turn over the engine - no spark at the plugs. Brake light switch and light works. Headlamp and tail lamp not working. Not too bad for a first timer! LAB any suggestions on the headlamp and tail lamp not working? I figure it's a misplaced wire, but without going through the diagram I'm not sure. I'm going to take a wee break to let the Force (or LAB) deliver the answer to me....

Cheers,
Rob

Oh yeah, and my horn doesn't work either.

Starvingphotog said:

Headlamp and tail lamp not working. Not too bad for a first timer! LAB any suggestions on the headlamp and tail lamp not working? I figure it's a misplaced wire, but without going through the diagram I'm not sure.

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The headlamp UY (as there's no switch terminal 4) and tail lamp NG (also instruments and pilot bulb if fitted) are powered from the master switch terminal 3 so that would be the logical place to start checking.

Starvingphotog said:

Oh yeah, and my horn doesn't work either.

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Is WR from the switch cluster connected to harness PB?

Have you tested the horn (battery test) as it could be a horn fault and not a wiring fault?

L.A.B. said:

The headlamp UY (as there's no switch terminal 4) and tail lamp NG (also instruments and pilot bulb if fitted) are powered from the master switch terminal 3 so that would be the logical place to start checking.




Is WR from the switch cluster connected to harness PB?

Have you tested the horn (battery test) as it could be a horn fault and not a wiring fault?

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Ok LAB, we're getting there!

Well, forgive me. It looks like the horn is shot. Stupid me. I should have tested it first. I read 12V when I measure the two wires with the horn button pressed, so the wiring is correct. That should solve the horn issue as soon as I can get a new horn.

Now, the lights. I had a solid blue wire for power and it wasn't connected to anything on the main loom. Replaced it with a blue yellow and I have main beam now. Still no tail light though. The ignition switch is correct with the UY/NG on terminal 3. I just confirmed it. I decided to use the two-position toggle switch to turn on the main headlights. I'm not sure what's up with the tail lights though.

Starvingphotog said:

Now, the lights. I had a solid blue wire for power and it wasn't connected to anything on the main loom.

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The headlamp harness U should be connected to LG/N of the switch cluster, not the main loom (no U in the main loom).

As you are using the 'wrong' (direction indicator) switch cluster to power the headlamp, except for W, the switch cluster wires connect to wires of a different colour...so:

Switch Cluster Wires:
WY...connects to harness WU (apparently ok as the ignition and kill switch work and WY-WU is normal).
WR...connects to harness PB (circuit apparently ok although the horn itself isn't working).
LG/N...connects to headlamp harness U (power to the switch cluster, now 'Hi-Lo' toggle from the headlamp switch).
GW...connects to headlamp harness *UW* (power from the switch cluster to the bulb high beam filament).
GR...connects to headlamp harness *UR* (power from the switch cluster to the low beam filament).

*(Suggested connections as it can also be GW-UR and GR-UW according to toggle switch position preference for Hi-Lo).

Starvingphotog said:

I'm not sure what's up with the tail lights though.

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I can only suggest you check the tail lamp connections and NG wire also the lamp 'ground' connection.

Yes sir! Ok. Figured the rear lamp. Wrong wires. red green instead of brown green....Yikes!

I'll try rewiring the headlight harness now according to your directions LAB and see what happens...

Cheers,
Rob

Hey there LAB, with the above guidance is the solid White wire from the main harness still connecting to the Switch Cluster White wire?

Starvingphotog said:

with the above guidance is the solid White wire from the main harness still connecting to the Switch Cluster White wire?

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Yes, as W is power for the kill switch WY (and so is the power supply for the ignition) also the horn WR-PB.

Well LAB! All done! All lights work. Plugs spark. Kill switch works. I'll get a new horn tomorrow and that should work fine since I get 12V measured when the button is pushed. I had to move the high-beam to the toggle switch on the headlamp. The upward toggle on the Switch Cluster was flaky and doesn't work consistently. Bulb is fine and both lights work well with this setup.

Next is to zip tie some cables, prepare the new mounting kit for the tank and install it, continue cleaning up the engine and install the oil filter kit. I have a cNw breather kit that I might get to as well! I'm anxious to take it out for a spin once I make sure the rear wheel is aligned correctly - I had to take it off earlier and disturbed the adjustment screws from their previous settings.

LAB, thanks again for your help here man! You really know your stuff!

The adventure continues.....

Cheers,
Rob