C15 alternator

[bushy]

Hey everybody, 1959 c15 star, is there a way of identifying the three output wires from the alternator?
My ones do not relate to any other wiring schematic so I cant connect up in fear of messing it up . :/
Many thanks if you have an answer ...   

[berniej]

Can you see what colour the original wires are? They may have been chopped back and extended at some point but I would guess that you still have the original wires close to the stator.
They can discolour over time but hopefully you can clean up a bit and see what the original colours were? That would be a help in identifying what goes where.

Cheers,
Bernie

[berniej]

Also.... just realised that you posted under 'Forum problems'!
Maybe 'Singles' would be the best place....

[Colin SS90]

If you have a multimeter you can identify the wires by checking the resistance between pairs of wires. This is how I identified the wires on my SS90 which had red, green and black wires, which after checking were identifed as black being common and the other two being joined for 12 volt.

Identify the wires as A, B and C.
Check and record the resistance between A-B, A-C and B-C.
The pair with the highest resistance are the outputs from the coils and can be joined together for a 12 volt system using a modern regulator and rectifier and connected to green/yellow. If you want to stay as original see below.
The remaining wire is the common to be connected to green/white.

To identify the wires for original switches.
The pair with the lowest resistance reading are common (green/white identifed as above)  and green/black.
The pair with the middle resistance reading are common (green/white identified as above) and green/yellow.

Hope this helps.

[bushy]

Thanks for the replies:

original colours coming out are Grey  Blue  Brown .

The Dragonfly loom I have has  Greenbrown  White green  green yellow.


Can't see why they could match the original unless mine isn't

I Will get the multimeter out 6v stator 

[JulianS]

The colours of the output cables varied over the years due to some of the early ones fading or otherwise deteriorating and Lucas changing them to rectify.

The information below comes from the Lucas Alternator service manual from 1971 and shows how Lucas changed the colours changed over the years.

[bushy]

I have checked  the resistance now :

AB=9   AC=1.5   BC 1.2

Can I joint ac bc to get the 6v ?

I know that 4 coils are for the running with the extra 2 for the lights and emergency starting ie battery flat ..

Thanks on advance

[Colin SS90]

From your readings for 6v I think the connections should be

C - common (Dragonfly green/white)
B - normal running (Dragonfly green/brown)
A - extra power for lights (Dragonfly green/yellow)

The original light switch is used to introduce the extra power circuit when the lights are switched on.

[Colin SS90]

Just looked at your resistance figures again, I would expect the two lower figures when added together would roughly equal the highest reading. This is because the two lower figures are separate coil resistances and the higher figure is the resistance through both sets of coils. This may mean that the stator is faulty, or a bad contact on the common circuit.

These are just my thoughts, if anyone has a loose stator perhaps they could measure their resistance figures for comparison. I've looked at my notes from rebuilding my SS90 and although I can remember measuring the resistance, unfortunately I did not record the readings.

[JulianS]

These figures from a Triumph bulletin in 1965 may help if you can match your stator number with those in the bulletin.

The 1962 on C15 with RM18 alternator originally took stator 47161 on the second page.

[bushy]

Thanks for that - from recall the stator has no id makes on - if it has, will take off the primary case - is it certain it has ID's ?
Haven't got my notes with me in the house so can't check the figures ...

[JulianS]

Should be somewhere on the laminated frame, probably a date also.

Whatever the resistance measures cold is no guarantee the insulation will not breakdown when hot.

[bushy]

Any way of testing it while it's on - other than testing the resistance ? If I turn it over there should be a voltage ?

[Colin SS90]

The only certain way to test it is to assemble the alternator into the bike and connect the wiring, then start the engine and test the outputs to the battery. This will not only check the stator and wiring, but all of the other electrical parts as well.