Just purchased a new 3 phase Sparx alternator from Commando Specialties ( great service )

I realise that the three wires from the alternater go to the three yellow wires on the reg./rect. and the red goes to earth ( ground in American).
If the bike's wired pos. earth ( ground )

My question is where does the black from the reg./rect. join the wiring harness ? My quess would be it joins to the brown and blue where the old rectifier once was, and the white and green and the green and yellow would become redundant ?

The old zener diode wiring can be snipped off too ??

I hope someone can confirm this. Or deny it and explain what really happens.
Thanks in advance. Col

Combat Col wrote: My question is where does the black from the reg./rect. join the wiring harness ? My quess would be it joins to the brown and blue where the old rectifier once was, and the white and green and the green and yellow would become redundant ?

Yes, although theoretically, you could connect black to the brown/blue anywhere between the main fuse and the ignition switch.

Combat Col wrote:The old zener diode wiring can be snipped off too ??

Snip or tape up the wires, it's up to you, just make sure the Zener brown/blue wire can't short to earth.

the black can go straight to the battery?

pelican wrote:the black can go straight to the battery?

It can, but then the reg/rec unit and it's wiring will not be protected by the fuse.

You don't want the alternator feeding the load side of the power circuit, because then it won't be switched!

I like running it through it's own fuse and straight to the battery.

grandpaul wrote: I like running it through it's own fuse and straight to the battery.

I agree. I'd use an inline fuse there too.

Coco wrote:

grandpaul wrote: I like running it through it's own fuse and straight to the battery.

I agree. I'd use an inline fuse there too.

Personally, I've never liked the idea of multiple wires connected to battery terminals, and I would always avoid doing that whenever possible.

The alternator charging wire needs to go to the battery side of the fuse or to a fuse of its own. If the alternator charge wire goes to the harness side of the fuse then a short in the bike will not be protected from the alternator output and may result in a fried harness. Jim

comnoz wrote:The alternator charging wire needs to go to the battery side of the fuse or to a fuse of its own.

However, no standard Commando has its alternator output connected to the battery side of the main fuse.

comnoz wrote:If the alternator charge wire goes to the harness side of the fuse then a short in the bike will not be protected from the alternator output and may result in a fried harness

I don't think the alternator would be capable of producing that much output?

With alternator output connected to the battery side of the fuse, if a short developed in the wiring harness, then the battery amps should blow the fuse-and the bike would stop running.
As I see it, if alternator output is connected to the side of the fuse away from the battery and a short occurred in the harness then the battery amps would blow the fuse as usual, but alternator output would be barely enough to supply the electrical loads from the ignition and lights etc. and a short would result in the alternator's output going straight to earth/ground, so the engine would also stop running = so no alternator output - no fried harness.

That was mostly true with an original alternator. However with a 3 phase it it capable of putting out enough currant to smoke the 16 gauge wiring in a Commando. As you are riding down the road the alternator is what is supplying the power to run the bike, light the headlight and at the same time put a half an amp maintenance charge into the battery. If a short develops back by the tail-lamp the regulator just sees that as additional load and so ramps it's output to full on and then the 20 or so amps supplied by the alternator is more than enough to burn wiring and keep the voltage high enough to keep the bike running.
A few British bikes are the only vehicles, cars or bikes, who run the alternator to the harness side of the fuses. Nearly all vehicles run the alternator output directly to the battery with no fuse. Jim

comnoz wrote: A few British bikes are the only vehicles, cars or bikes, who run the alternator to the harness side of the fuses. Nearly all vehicles run the alternator output directly to the battery with no fuse.

Agreed, but then most vehicles do have much higher output alternators-far higher than even the three-phase Lucas/Sparx type!

Sparx quote a maximum of "15.38A" for their three-phase alternator. http://www.tri-corengland.com/acatalog/ ... lts_1.html

L.A.B. wrote:

comnoz wrote: A few British bikes are the only vehicles, cars or bikes, who run the alternator to the harness side of the fuses. Nearly all vehicles run the alternator output directly to the battery with no fuse.

Agreed, but then most vehicles do have much higher output alternators-far higher than even the three-phase Lucas/Sparx type!

Sparx quote a maximum of "15.38A" for their three-phase alternator. http://www.tri-corengland.com/acatalog/ ... lts_1.html

That is correct, so you have 15.38 amps from the alternator and then the battery can contribute up to 10 amps before the fuse blows so then you have 25.38 amps available to burn things. Granted if the wire suddenly shorts directly to ground the large surge of currant would likely overcome the alternator and fuse and stop the engine dead. Unfortunately the more common scenario is the wire insulation rubs through and the currant draw through the short rises slowly and that is when the problem will occur. Jim

Thanks for all the replies.
I decided to go straight to the battery with a dedicated fuse. This seems to take the warning light assimilator out of the picture. Do I now need to join the green/yellow to the brown/blue to make the ignition light go out when the engine's running ? I'm getting 14.5 volts at about 4000 rpm. Appreciate your help. Electrics are not really my game.

Combat Col wrote:I decided to go straight to the battery with a dedicated fuse. This seems to take the warning light assimilator out of the picture. Do I now need to join the green/yellow to the brown/blue to make the ignition light go out when the engine's running ?

The green/yellow from the assimilator needs to be connected to one of the alternator output wires.

[Edit] I seem to remember that the original assimilator may not be compatible with some reg/rec units, so let us know if it doesn't work?

Thanks L.A B. worked like a charm. As far as I know it's the original assimilitor. Problem solved, now on to the next one ...
Cheers Col