MkIII Harness wire landing questions

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Finally got back to working on the MkIII wiring and have been studying the wiring diagrams. I am working with a Lucas harness 066396 and do not understand what the "Power Point" is.

Could this be the Power Takeoff referred to in section J for 12V accessories?

We also have 3 wires coming off the harness labeled "Starter Motor". I cant find any details of where or how these wires are landed. All I have on my starter is a nut on a stud on the very top. Diagram shows some kind of device and spring above this nut, don't know what those are.

Your help would again be appreciated.
 

L.A.B.

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Finally got back to working on the MkIII wiring and have been studying the wiring diagrams. I am working with a Lucas harness 066396 and do not understand what the "Power Point" is.

Could this be the Power Takeoff referred to in section J for 12V accessories?

Yes, and would be a brown/blue and a red.

We also have 3 wires coming off the harness labeled "Starter Motor". I cant find any details of where or how these wires are landed. All I have on my starter is a nut on a stud on the very top. Diagram shows some kind of device and spring above this nut, don't know what those are.

WW19132_282_29.JPG

Edit: The wires on the Trust Lucas diagram marked "Starter Motor" are the starter motor solenoid wires but don't connect the white/purple if your Mk3 has electronic ignition. I also recommend that you do not connect the red "Battery" wire to the battery positive terminal, only connect the heavy starter positive cable.


The "device and spring above the starter nut" sounds like the early 3AW 3-wire assimilator which your harness probably has no connections.

The two brown/blue and red, marked "Capacitor" on the Trust Lucas diagram connect to the 2MC 'blue can' on a spring in the battery compartment.
 
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Yes, and would be a brown/blue and a red.



WW19132_282_29.JPG

Edit: The wires on the Trust Lucas diagram marked "Starter Motor" are the starter motor solenoid wires but don't connect the white/purple if your Mk3 has electronic ignition. I also recommend that you do not connect the red "Battery" wire to the battery positive terminal, only connect the heavy starter positive cable.


The "device and spring above the starter nut" sounds like the early 3AW 3-wire assimilator which your harness probably has no connections.

The two brown/blue and red, marked "Capacitor" on the Trust Lucas diagram connect to the 2MC 'blue can' on a spring in the battery compartment.
That diagram only shows connections for one of the two Zener diodes.
 

L.A.B.

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That diagram only shows connections for one of the two Zener diodes.

It does show connections for two Zeners although one with what looks to be white instead of white/green.
 
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What I actually have is a pair of yellow greens coupled to one connector and a pair of red grounds to one connector on the right side. Left is similar only it has a pair of whites to one connector and the red grounds. I have fasted the grounds under the Zener Diode on its lug.
 

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What I actually have is a pair of yellow greens coupled to one connector and a pair of red grounds to one connector on the right side.

A pair of green/yellow wires to the RH Zener is correct.

Left is similar only it has a pair of whites to one connector and the red grounds. I have fasted the grounds under the Zener Diode on its lug.


The pair of white wires to the LH Zener should be white/green and appears the error is in the 'Lucas' harness as well as the diagram but their diagrams often contain errors (can't even spell Zener correctly!) as "Classic Lucas" is really Wassell.

The LH red ground terminal should be fitted under a thin locknut, item '18' (06.1247) on the inside of the LH footrest mounting bolt '17' adjacent to the Zener diode, see the link, below, Edit: Nut 18 is drawn in the wrong position looking as if it belongs behind the RH Z-plate but listed in the parts book as "Nut L.H. Footpeg" ...
White at the Zener diode might indicate that the connections to the alternator stator, rectifier and warning light assimilator could also be incorrect white instead of white/green.
1975-MK3-Commando-Original.png



...and the most convenient location for the RH ground is on the inside of the three-way T-piece assembly '22'-'26' as neither ground terminal should be fitted between the Zener and the Z-plate (see Mk3 manual, section J5).
 
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Your assumption is partially correct, we got a white and gr/yellow to the alternator but the rectifier has gr/yellow and gr/white. On the alternator we attached the white to the gr/white coming out of the primary case. I'll correct the ground locations near the Zener diodes.

I removed the starter, I'm still puzzled as to what engages it and what/where wires connect to it. The Lucas diagram gave us a purple/white, red/white, and ground to starter motor. In reality we got a blue/white, red/white and ground? Maybe they ran out of purple/white wire?
 

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I removed the starter, I'm still puzzled as to what engages it and what/where wires connect to it. The Lucas diagram gave us a purple/white, red/white, and ground to starter motor. In reality we got a blue/white, red/white and ground? Maybe they ran out of purple/white wire?
As I said previously, those wires go to the starter solenoid not the starter motor. The solenoid is (or should be?) in the battery compartment attached to the frame plate. A heavy (-) cable should go from the solenoid to the starter terminal stud.
Connect the white/red to the solenoid 'S' terminal and what should be white/purple to the 'I' terminal but only if it has points ignition. Red ground to a solenoid bracket bolt or other convenient attachment point close to the solenoid.
 
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I missed your previous reference to the solenoid. There was none on the bike but in digging through parts boxes I found one, had to look up what I was even looking for and thank you for the wire termination help.
I'll try to find some pictures of of the usual mounting you mention in the battery area, this clears up a lot!
 
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Thanks to your posts and photos I now have the grounds on the Zener diodes corrected, I formed a bracket like the one pictured and the solenoid is now mounted with the smaller wires attached in the same location shown above.

As you mentioned, a larger cable should go from one of the large posts on the solenoid to the starter motor post. It's unclear to me from the wiring diagram it looks like the other solenoid post may go directly to the (-) battery post? A recommendation on cable size for both would be appreciated.

I also have a large brown wire that is mounted on the back of the engine that looks like it could easily reach the battery, I'm wondering if this isn't intended to be landed on the battery (+) as a good solid ground?
 

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As you mentioned, a larger cable should go from one of the large posts on the solenoid to the starter motor post. It's unclear to me from the wiring diagram it looks like the other solenoid post may go directly to the (-) battery post?

Correct. Also connect the fused brown/blue from the harness to battery(-).

A recommendation on cable size for both would be appreciated.
=
I also have a large brown wire that is mounted on the back of the engine that looks like it could easily reach the battery, I'm wondering if this isn't intended to be landed on the battery (+) as a good solid ground?

That sounds as if could be the heavy gauge positive cable...

...if so, then it should be connected to battery(+) but preferably replaced with a heavier gauge wire.

I strongly recommend that you do not connect the harness red (ring terminal) to battery(+).
Fit only the heavy gauge positive cable to battery(+) and ensure the harness red has a good connection to the engine as under certain circumstances, the 100A+ starter current can potentially burn out the harness wire if it is attached directly to battery(+)!
 
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Just to confirm the red I have taped with the brown/blue coming out of the harness together should not attach to the battery but to another ground location.
And yes the cable you identified on the engine bolt is the one I was referring to, I'll send it to the battery.
I'll start looking for larger cables per the recommended photo you attached!!! I don't think we have any cables in our stash so we need to purchase anyway.


Nort2.jpg
 

L.A.B.

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Just to confirm the red I have taped with the brown/blue coming out of the harness together should not attach to the battery but to another ground location.

The red doesn't need to be connected to ground although you can if you like.
It can just be taped up as it is an electrical 'mistake' to have a harness ground (either positive or negative) connected directly to the battery terminal if the bike has a working starter motor.

I'll start looking for larger cables per the recommended photo you attached!!! I don't think we have any cables in our stash so we need to purchase anyway.
The photo was from dynodave's shop.
 
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