BSA Owners' Club Workshop Discussions

The BSA Workshop => Singles => Topic started by: bushy on 20 Sep, 2025, 18:20

Title: Alternator wires
Post by: bushy on 20 Sep, 2025, 18:20
Have blue, brown and white wires coming from the alternator ! No mention of these combination anywhere..
1959 star

Would add a pic but can't see how , sorry
Title: Re: Alternator wires
Post by: Derek996 on 21 Sep, 2025, 09:34
Possibly the original wires have been replaced at some time. This is the normal wiring.
Title: Re: Alternator wires
Post by: limeyrob on 21 Sep, 2025, 10:25
I was thinking the same thing. Does anyone know the coil resistances?  With those it my be able to work out which is which.  Any sign of a join where you can get a glimpse of the original colours (if they have been changed)?
Title: Re: Alternator wires
Post by: DAVE BRADY on 21 Sep, 2025, 10:38
Hi,

Is it open coils or encapsulated?  With bare coils it may be possible to follow the wires to see how they are connected.

Dave.
Title: Re: Alternator wires
Post by: JulianS on 21 Sep, 2025, 11:34
I would remove the stator and check for a Lucas part number, which will probably be stamped on the outer edge of the laminations, then at least, you will know what it started out as. You will also find a part number on the rotor.

Most of the Lucas alternator stuff focuses on outputs rather than resistance but the below Triumph bulletin from 1965 does gives some resistance figures if you can match your stator number to one of those listed. If you do test the resistances I would suggest that you do it after removing the stator and checking it carefully on both sides.
Title: Re: Alternator wires
Post by: limeyrob on 21 Sep, 2025, 17:48
That's a very handy chart!!
Title: Re: Alternator wires
Post by: bushy on 22 Sep, 2025, 10:29
Thant's a great help , thanks , will keep posted !
Title: Re: Alternator wires
Post by: bushy on 22 Sep, 2025, 14:25
Primary cover off and these are the colours , wrong I think however is there hope ?
Title: Re: Alternator wires
Post by: limeyrob on 22 Sep, 2025, 16:21
They look DIY soldered so if you can get a pic of a similar alternator you may be able to work out what is what.  Get a new nut on the crank, nuts like that can have nasty sharp edges.  The nuts seem to be barely on the studs.  Is it part off or is something else going on?
Title: Re: Alternator wires
Post by: Derek996 on 22 Sep, 2025, 16:29
The wires have obviously been replaced with non standard ones. I'm sure some one on here will be able to tell you which colour should go where.
Title: Re: Alternator wires
Post by: DAVE BRADY on 22 Sep, 2025, 16:42
Hi,

Does this help?
Title: Re: Alternator wires
Post by: bushy on 22 Sep, 2025, 18:04
Thanks,  they all seem to be green ! the rectifier only has two connections so three into two another issue...
Title: Re: Alternator wires
Post by: DAVE BRADY on 22 Sep, 2025, 21:14
Hi,

They are GN/BK, GN/Y and WT/GN.  The cover is back on now so I cannot take a better one.

Dave.
Title: Re: Alternator wires
Post by: Derek996 on 23 Sep, 2025, 09:25
The left hand appears to be green/yellow and the right hand one green/white. So presumably the centre one is green/black although it's hard to tell from the photo.