Wiring from dynamo issue

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G3L1946
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Wiring from dynamo issue

Post by G3L1946 »

Hi all,

Advice please. My dynamo, E3N - LI with number 20038B stamped thereon, has a red wire and black wire coming from it and I’m confronted with green and yellow ( green to F and yellow to D ) from the manual. Can anyone advise me which wire goes to D and F on the regulator? Or, is there a simple way to test which is which?
The wires ( red and black ) appear to be original.

Thanks,

Steve
Groily
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Re: Wiring from dynamo issue

Post by Groily »

Green for F and Yellow for D would be standard, but who knows what has been used by people over the years? The only sure way to KNOW, even if there are the letters D and F stamped on the bakelite cover pretending to tell us (and maybe even correctly!), is to take the cover off and see where the two wires come from.
One will come from 'inside' the dynamo main body, through the brushplate. That will be 'F'. The other will come, maybe via a bit of bracketry, from the D brush. That's your D. They hook up to Regulator F and D respectively. Reversal will screw things up, so best check.

Whether the thing works, and whether the regulator is any good, are separate matters, but give it a whirl. If there's no output, come back and there will be more to add!
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G3L1946
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Re: Wiring from dynamo issue

Post by G3L1946 »

Hi Groily,

Thanks for info. The regulator is not quite ‘standard’ as it’s a Lucas RB108 which, I’m reliably informed, is suitable. I think the MCR2 was originally fitted. The dynamo ,also, is a bit non conformist! It has a metal cap as opposed to a Bakelite one with no markings.

Thanks again,

Steve
Greybeard
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Re: Wiring from dynamo issue

Post by Greybeard »

You could do worse than get yourself a copy of this book, Stevs


or visit
https://www.matchlessclueless.com/

Steve
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G3L1946
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Re: Wiring from dynamo issue

Post by G3L1946 »

Hi Greybeard,

I have Roy Bacon and Nigel Clark’s books so this might make a nice addition. I looked on clueless.com but could not find the answer to my question. I might have missed it, I’ll take a second look. I also referred to the Lucas manual on dynamos for the answer but no help.

I’ll look further as Groily suggested,

Thanks, hope the East of Gods county has better weather than the North!

Regards,

Steve
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Rob Harknett
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Re: Wiring from dynamo issue

Post by Rob Harknett »

You should state Make, year, model of your bike.
Groily
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Re: Wiring from dynamo issue

Post by Groily »

Whether the end cover is steel or bakelite won't affect things.
With the later tin end cover, the wires come out through a grommet to go off to the regulator but are pushed into female sockets on the upper side of the brushplate inside under the tin thing. One being F, one being D.
The brushplate will probably be marked D and F.
The D socket will have a tang on it connected to the tail end of one brush. The D brush. Or should.
The F socket will have a tang on it connected to a wire that emerges from within. (Hopefully the right one of the two that so emerge.)
So the F and D thing is exactly the same with either type of dynamo end cover, just it's hidden from view with the tin one.

There will also be two wires screwed into the metal of the bearing housing to earth - the tail of the Earth brush, and the other field coil wire, that also comes from the depths.

The field coil wires - one to F terminal, one to Earth - don't want messing with, unless we have to come to that later. Swapping them reverses the rotation of the thing.

Polarity is the other thing that matters - ie positive or negative earth? If nothing has been touched, it should be however the battery terminals are wired - either + or - to earth. Either will do equally well, but the dynamo needs to be set to suit if it's not known or if we're in mix n match territory, and an electronic regulator must match the choice of earth as the way they work isn't a question of choice. The MCR and RB mechanical job are interchangeable, and not polarity sensitive, so no prob there - IF it works. Primitive things, but can be very durable.

The books will tell you that in standard Lucas systems one brush goes to D, one brush goes to E(arth), one field coil wire also goes to E and the other one to the F terminal. That's all there is. The colours that have been used to hook the dynamo to the voltage regulator aren't important as long as D goes to D and F to F, dyn to reg.These would usually be Green for the F wire to the regulator and Yellow for the D wire. But all sorts can be found, as you have discovered!.

The field coil wires are the same colour in the dynamo and the brush tails are usually blue, or some sort of yellowish spirally stuff. All that's needed is to see which socket on the brushplate under the cover is marked D; make sure it's where the D brush is connected; and make sure the wire from the field coil (the one that comes from inside the body) goes to the F terminal. And then that the regulator is connected D-D & F-F.

----------------------

Having said that, there are other ways of doing things and some voltage regulators (JG ones, Wassell negative earth electronic ones, some 'continental' gizmos), require different internal wiring at the dynamo. This is what used to be called the difference between 'shunt' and 'series' wound dynamos or Live side and Earth side regulation, and only something to come to if there are further complications. But Miller, and all furriners, did things differently. The good and the bad news is that any dynamo just about can be made to work in either fashion, with either earth, either direction of rotation, so it's something that may have to be borne in mind.
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G3L1946
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Re: Wiring from dynamo issue

Post by G3L1946 »

Hi Groily,

Well, If I can’t work it out from that I’ll give up! Thanks, very comprehensive and appreciated. My only mention re tin cover was that it has no markings as I assumed, by your earlier reply, that the Bakelite ones did. I have replaced the old wiring with a new loom and worked everything else out O.K. using the original wiring diagram from the 1955 manual.
Rob, as ever, thanks for the links. Will take a read tomorrow.

Regards to you both,

Steve
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Re: Wiring from dynamo issue

Post by Mick D »

Hi

Photo attached showing RB108 regulator terminal identification:
RB108 Bottom.png
Regards Mick
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