Mach 1 Electrical Question

[blaat!]

Hi All,
Let me preface this by saying I bought the bike as a basket case, and the harness and headlight were purchased separately. It isn't shown in the photos, but please keep in mind that the wires coming out of the headlight are cut, and not connected to the harness, but the harness is complete(ish) with bullet connectors that will eventually get routed and connected into the headlight. I'm going through the electrical at the moment and most of it is making sense so far. There is just one area I can't figure out.

The white wire comes out of the harness near the coil and has an eye terminal just as you would expect based on the wiring diagram. A black wire also comes out near the coil, and the other end goes to the headlight end of the harness:

coil-wires.jpg

Based on the wiring diagram the black wire at the coil should go to the points, not the headlight (top left, I drew a red arrow):

schematic-2.JPG

In the headlight, there is one wire that doesn't show up on the wiring diagram (fourth from the left, circled in red):

headlight.jpg

My (probably incorrect) theory is that at some point Ducati started routing the wire from the points through the headlight terminal block and back to the coil. On the wiring diagram there is one spot that is open on the headlight terminal block, but it has a wire connected to it in mine. This theory kinda falls apart though because that terminal location has a wire connected to the back side that seems to go up toward the switches.

Any ideas what I'm missing? I could just wire it like the wiring diagram, but I don't want to mess with the harness if it is right, and what is that last wire in the headlight terminal block that doesn't show up on the wiring diagram?

Thanks for any help!
Jim

[George]

I think that the black wire with eye is an earth connected to frame / coil fixing bolts. Other end is connected to headlight bulb via bullet connector shown in diagram at number nine as black earth connection.
White wire to coil. There should be a separate black wire from points to coil

[JimF]

I’m going to have to go back about 20 years in my notes because this all seems so vaguely familiar. I seem to recall a wire at the terminal block on my Mach 1 that wasn’t in that wiring diagram you are using (the same one I used).

Without looking at my Mach 1 or finding my notes, I am thinking that the white wire may have been routed to the bucket for a kill switch circuit that was never implemented.

If the white wire and the black wire were both on the same coil post, then a momentary contact SPST push button kill switch could have been connected to the white wire and the other end of the switch to ground so as to kill the ignition if the button were held down.

Jim

[JimF]

download/file.php?id=2022&mode=view

Looking at my notes I have a black wire with a white stripe that goes to the terminal block position that is depicted in the wiring diagram as having no connection.

The other end is connected to the frame at a bolt securing the ignition coil, This matches what George said in his reply.

Maybe the idea is to have a reliable zero-ohm dead short frame ground connection inside the bucket that bypasses the steering head as the grease-laced steering head bearings which could present a poor (resistive) electrical connection.

Jim

[nalimugmug]

Hi,

I can confirm whats already been mentioned.

Just checked on my Mach 1-

Of the two cables in your pic, the black one goes into the empty slot in the headlight, white one to coil.

Excellent diagram from Jim.

Cheers

Bob

[blaat!]

Ah, that makes so much sense. It also explains why the two eye terminals, that both go to the coil, are different styles. That was bugging me too.

George for the win. Thanks for confirming Bob.

I see it clearly called out in your notes too Jim F. Those notes are great. You should post them along with the wiring diagrams in the tech section of the site.

This will save me from wasting time and unnecessarily making modifications to the wiring harness. And progress continues!

Thanks again.
Jim

[blaat!]

Okay 10 years in I shouldn't still be asking stupid newbie questions, but here goes anyway...

Is this position one or three on the headlight commutator?

commutator-position.jpg

In other words, is this the parking light setting, or the headlight on setting?