Wiring My Alternator

[demonboy]

I have a couple of problems.

1. The first is that my schematic I drew before taking off my Lucas 50amp. alternator has gone walkies, so now I am left puzzled by the rewiring of it. The two labelled terminals are 'B+' and 'W'. Confirmation of the following points would be appreciated:

- I have the positive which will go from terminal B+ to my new Sterling split charger.
- Then there is a negative which comes from the starter motor, which I think was attached to the body of the altrn8r - does this sound right?
- A third wire must be my ignition
- I have a fourth thin wire that I simply cannot trace. Any clues?
- Was 'W' field? Where does that go?

2. I'm having a new Lucas TVS 90amp altrn8r fitted but the back of it looks nothing like my old alternator. From what I can see there is only one terminal, which has to be the positive. There appears to be a couple of small terminals surrounded by a plastic casing which looks like it should be a plug of some description.The alternator man here assures me he can bypass the internal regulator when my Balmar gets delivered but said it is constructed differently to the old alternator, which makes me nervous somewhat! This is obviously an automotive alternator so have I made a mistake in buying this, or are the terminals there but hidden? Is my paranoia justified or does this new alternator sound ok provided it is moderated correctly?

 

[bendyone]

W is for the rev counter.

 

[Billjratt]

You've removed an old Lucas. Was the sterling working with it?
You are fitting a bigger (probably more modern) Lucas with the field connector and live connector on a two-pin lucar connector.
The sterling requires another wire to the "high" brush - this would have already been added to the old one . (white wire)
What is the Balmar story? are you getting yet another alternator?
Balmar and some of the older Lucas alternators( with external regulators and relays) were only six-diode machines, and need another three inserted to work happily with the sterling.
Pictures would help

 

[demonboy]

You've removed an old Lucas. Was the sterling working with it?

No, the Sterling is a new addition that is being added at the same time that we're removing the old Lucas.

You are fitting a bigger (probably more modern) Lucas with the field connector and live connector on a two-pin lucar connector.

Not sure, my alternator man has not shown me this but I am guessing this is the case. Can anyone confirm this?

The sterling requires another wire to the "high" brush - this would have already been added to the old one . (white wire)

Does it? The Sterling simply has a positive from the alternator to the Sterling, and a ground.

What is the Balmar story? are you getting yet another alternator?

No, the Balmar is an alternator regulator (ARS-5)

Balmar and some of the older Lucas alternators( with external regulators and relays) were only six-diode machines, and need another three inserted to work happily with the sterling.

Not sure how this affects me. I will attempt to get some pics up...

 

[SHUG]

The usual coding is:
B+ or Batt ,Main output
B- or E to negative (earth)
D+ to alternator warning lamp this is L on Lucas alternators
F goes to the regulator
W to Tachometer (or sometimes a small jack plug)
B+ and B- may also be connected to the case via a supressor

 

[pvb]

I'm confused. Are you saying you're fitting a new alternator with a Sterling regulator and a Balmar ARS5???

 

[VicS]

I'm confused. Are you saying you're fitting a new alternator with a Sterling regulator and a Balmar ARS5???

IIRC he is fitting a Sterling ProAlt C Alternator to Battery charger. At least that is what he said in an earlier thread.

Now I do not believe that this should be used with the Balmar AR5S.

I would think that the Sterling unit on its own will acheive pretty much what the Balmar regulator does anyway.

If the Balmar regulator is fitted then a diode splitter or VSR is the way forward rather than the Sterling AB charger.
A good choice perhaps would be the Balmar Digital Duo Charge - DDC-12/24 to compliment the ARS5

 

[pvb]

IIRC he is fitting a Sterling ProAlt C Alternator to Battery charger. At least that is what he said in an earlier thread.

Now I do not believe that this should be used with the Balmar AR5S.

Correct. There's no point having both. Sounds like he's being badly advised.

 

[Billjratt]

Sorry. I thought he was fitting a Sterling digital alt controller!
Just shows - you've got to give a fair description if you want a sensible answer.

 

[demonboy]

*kicks self for not asking the question earlier*

I did wonder what the end-result would be of having both the Sterling and the ARS-5. I'm just annoyed with myself as we've ordered the Balmar from the States and we get whacked in the pants for import duties. Still, it means we have the Balmar as a back-up, nothing wrong with carrying a spare, but it's an expensive mistake to make.

The other thing is I've wired up my Sterling now, including the drilling of big holes and the ripping up of floorboards, so since adding the Balmar is a fiddly job anyway I'll stick with the Sterling.

Does that sound sensible?

BTW - not badly advised, just me not researching the subject properly. Remember in a previous thread how I had to be told three times that the Sterling is not a regulator? That's where my confusion began.

 

[demonboy]

Could someone confirm for me that it is normal to have a negative from the starter to the casing of the alternator. Cheers.

 

[demonboy]

Meanwhile, here are some images of the old Lucas as requested. They show a new regulator that's been fitted (they couldn't source the correct reg).

Apparently the W terminal is now obsolete so I have to use the new spade terminal on the new reg, I believe. Can someone confirm for me what the spade terminal is next to B+. Also the three spade terminals that are in a row, Picture 3, what are they and in what order? I know one of my thin wires used to go to the centre one, possibly ignition.

Hopefully I'll see the alternator chap this week and ask him to confirm. Photos of the new Lucas 90amp to follow...

1.

2.

3.

4.

5.

 

[demonboy]

Here is the new Lucas 90amp. Regarding the negative from the starter that I mentioned above, there is nowhere to put it on the casing at the moment. I'm guessing I could adapt the point in picture 2 (the one to the right)?

1.

2.

3.

4.

 

[VicS]

Automotive alternators are commonly earthed via the case and their mounting.

Some (better ones??) have an earth ( negative ) terminal! I've had alternators on flexible mountings where a separate earth connection was necessary.
Some ( boat) engines have a totally isolated negative ie do not use the block as the negative connection, then a completely separate negative connection direct to the alternator is needed.

Your new one must be earthed via the case and the mounting I hope your engine block is used as the negative other wise you have a further complication to sort out.

I am sorry I cannot help with the connections on the little 3 pin plug.

One presumably is the warning light connection, one may be the connection for a tacho, the other may be for battery sensing or a direct connection to the field ... I think you will have to get the wiring info from Lucas unless you can find it on a website or someone else knows

 

[BabaYaga]

Regarding your old alternator, the three in a row socket (two large spades, one small) is similar to what I have om my Iskra alternator.
The two large ones, which from the picture seem to be connected, should be the output, B+.
The small spade is D+ or ignition/warning light.
Some info in this link:
http://www.mgb-stuff.org.uk/altplug.htm
Sorry can't help regarding the new alt.

 

[demonboy]

Automotive alternators are commonly earthed via the case and their mounting.

Some (better ones??) have an earth ( negative ) terminal! I've had alternators on flexible mountings where a separate earth connection was necessary.
Some ( boat) engines have a totally isolated negative ie do not use the block as the negative connection, then a completely separate negative connection direct to the alternator is needed.

This is what I was saying, I have a negative which comes from the starter that went to the alternator but because I lost the schematic, I don't know where. If it goes anywhere, and it does not have a dedicated negative terminal, then it must just be attached to the casing. I was just checking that this made sense.

The problem is that I have no where to put this on the new alternator. Are you saying I probably don't need it because the new one is earthed within itself?

 

[VicS]

This is what I was saying, I have a negative which comes from the starter that went to the alternator but because I lost the schematic, I don't know where. If it goes anywhere, and it does not have a dedicated negative terminal, then it must just be attached to the casing. I was just checking that this made sense.

The problem is that I have no where to put this on the new alternator. Are you saying I probably don't need it because the new one is earthed within itself?

If there is no external negative terminal it must be earthed to the case internally.

This means you will be relying on the mountings and the bracket(s) to make a connection to the engine block ... It's OK ... perhaps a connection to an earth terminal would be better..
It also means that the engine block will used as the negative return. If it's wired with a direct connection from it somewhere back to the battery negative that's fine.

 

[demonboy]

OK, I think I understand now. As you suggest the engine block is the negative return anyway so the very fact the alternator is connected to the engine block completes the negative. I guess I just have to ensure that the none of these connections are painted. Meanwhile the common negative from the Sterling could be connected anywhere on that negative - the starter motor, directly to the engine block or even the negative on my domestic battery, right?

That's one problem cleared up.

What remains are two thin wires I had connected to the old alternator. They are coming from the same relay switch, but different terminals on that relay switch. One has to be ignition. What is the other? Is there any possibility the other is left over from my old external alternator regulator? What is that relay switch doing?

I have one theory: There is only one more wire, and that is ignition. However when the old external regulator was wired this wire was split, with one end going to the relay switch and the other going to the external regulator. Ironically the ignition wire is green, and so too is one of the wires coming off the relay. So, my question is this: does the ignition normally go via a relay before being connected to the alternator? If so then I think it's a case of wiring this green wire back together.

 

[VicS]

The instructions for the Sterling A-B charger say to extend and connect the negative wire directly to the alternator negative terminal or the case.

Sorry I cant help with the other questions in your post

 

[demonboy]

Thanks, Vic, you've been a great help already.

Perhaps you or someone else could help me identify the purpose of this relay switch. I suspect it may be something that's been added when the external regulator was added. I've drawn a simple schematic:

One of the terminals from the starter relay goes to this second relay. That in turn has two wires that go somewhere. I think one definitely went to the alternator but I have my suspicions that both went to the alternator. If so, what could they be?