Thanks Mur.  I've been in contact with Autosparks about this and they recommend running the wiring myself as you described.  All included with the correct color-coded wire, relays, relay sockets, integrated fuse-holders to send 12v to all relays with one larger amp rated cable from the starter solonoid, male and female bullet connectors and miscilaneous sleeve connectors, comes to around $60.  I'll still need to source some PVC sleeving to protect the wires. 

Before I started using relays with my old harness, there was a noticeable drop in headlight brightness when I turned on my heater motor, fog lights or honked my horn.  After relays, this went away.  Even though the switches could handle it, I'd rather reduce the amp draw through the wiring harness. 

Horn, high and low beams can all terminate as normal at the slam panel end of the harness.  Have a sense wire with female bullet or the appropriate spade leave these terminals and go back to trigger the relay.  Then, the load side of the relay goes back to the same point and then powers the device, be it the high/low beams or the horn.

Autosparks are quite happy to add relays, and to keep it in a period style for MK I cars I am sure they would have a solution, and it would be about $8.oo  All that aside; you can put the relays in the same place, feed them via a breaker, have them all mounted in neat mount blocks, and finally do a tidy sub harness to hold all of the relevant wires.

But as keen as I am about relays, the MK I switches are far more robust and I don't have any on my early cars.

To add to Kevin's comments, on many alternators two heavy wires leave the alternator.  One is the actual output cable and the second is the sense wire.  The sense wire is really supposed to be routed back to the battery and is part of the feedback circuit.  Where people fit alternators to early cars built with generators, the sense wire is often not used or it is looped back directly to the main alternator output.  In short, the sense wire often is used as a secondary output wire.

The small wire for the lamp is not just an indicator (at least not for Lucas alternators), it is part of the charging circuit.  With a Lucas (and many early GM alternators) if the warning lamp fails the alternator field coils are not powered during engine starting.  Without the coils being energized on engine start the alternator will not start charging the battery.  For Lucas alternators, the warning lamp needs to work for the system to charge.  I do not know if that is true for the Saturn/Bosch alternator.

 

Craig, there are 2 brown wires, simply to carry all the alternator output current. (Early Lucas 15AC only had 1 wire as it was low output).

The small brown/yellow wire has 2 functions on a Lucas alternator:
1. It feeds +12V to the alternator field via the charge lamp filamentwhen you turn ignition on, the alternator will not charge without this connection (early Lucas ones, anyway).
2. It lights the charge lamp when output fails, so you know when there is a problem.

I'm really wondering why Lucas would have 2 larger gauge brown wires that go to the same place at the solonoid, and mostly what function the smaller one has in the alternator?  I'll just put them together at the single + terminal at the alternator and at the solonoid. 

On another wiring subject, I used a fair amount of relays with the old harness - which I put inline wherever 12V supply was most accessible.  I had a relay for low beams, for high beams, fog lights and one for each set of air horns.  If I put the relay near the item to be powered, my harness will stay the most intact, but I will have to run my 12V to each relay and then out to the accessory.  If I bunch all relays in one location, I can get away with one larger 12V cable to the relay cluster, but I will have to cut the new harness to run each wire into each relay and then continue on to the accessories to be powered. 

I'm curious to know what others have done? 

The two brown wires are, well, both brown.  The brown with yellow is the alternator light.  place ring terminals on both browns for +12V and then fit whatever you need to the third.

Good idea about using connectors off of the alternator that plug into the Lucas plug. The Saturn alternator has 2 wires only: one to the solonoid (battery cable) and one to the charge indicator light. The wiring diagram will tell me where the other wire goes. Thanks!

"... This must be a Lucas plug type I'm assuming? My alternator is a Saturn 100 amp, so as much as I hate to cut the harness, I'll have to put the Saturn plug on it.."

I would try to find out if the "other end" of that Lucas connecter is available. Perhaps you could wire from that into your Saturn alternator. That way, if you or the next guy decide to change to the Lucas alternator, it'll just be plug 'n play.
Just a thought.

Since you have specified a loom for an alternator the connectors at the "other end" should tell you where the wires are supposed to terminate.  You are correct that the small wire will go to the warning light.  The two heavy gauge wires are likely to terminate at the starter solenoid terminal where all the brown wires attach.

You can always change alternators.

Thanks all, yes I specified an alternator and it's an Autosparks loom.  This must be a Lucas plug type I'm assuming?  My alternator is a Saturn 100 amp, so as much as I hate to cut the harness, I'll have to put the Saturn plug on it.  

I assume that the small wire goes to the charging indicator light, the large wire to the battery cable and where would the other one go?  I haven't looked at a later wiring diagram yet...

Thanks,

Craig

+3 on that being an alternator plug.  It is interesting to see one on a harness with the braided wire jackets.

It plugs into the alternator, which is obviously aftermarket. Oz Cooper S never got an alternator until 1969, and it was a 15AC with separate regulator. (I know your car is a `65 998 Cooper originally, these only had a C40 generator, aka dynamo). 

Did you specify an altenator when you ordered the loom? Autosparks will make the loom to spec.

Looks similar to an altenator plug.....but wouldn't be on a 65.
Voltage regulator.....?

 

 

( wiring......not my strong suit )

I'm looking over my new wiring harness before installing it and came across this plug.  It has two large gauge brown wires and one smaller brown/ yellow wire.  No where on the wiring diagram does it show two brown wires and a brown/ yellow coming into the same connection point and nothing like this was in the old harness.  

Can anybody ID it?