3 wire to 1 wire alternator

[cazman]

Yes, I am wondering how others hooked up these Denso alternators. I know others have used them.

Attached is the wiring diagram. As you said, FOTOG, there are only three wires shown including the large primary. The diagram shows a wire for the Light (NY) and one for the Ignition Power (NW). The Light wire in the car is always hot, so I hooked that up to the Sensor wire on the Denso. I hooked up Ignition to Ignition. So, where is the sensing circuit in the Europa? Internal to the alternator? The Indicator light circuit doubles as a sensing circuit?

[jbcollier]

You are installing an alternator that is not designed for this application.  You will have to adapt things to make it work.

- NY is indeed the feed from the warning light.  It is only powered when the ignition is on, and it is powered through a bulb.

- NW IS NOT IGNITION.  It is the main battery feed from the alternator to the ammeter.

Any wire designation that starts with N (brown) is an un-fused, connection to the battery*.  It is live all the time so tread carefully.  Ignition feed (unfused, switched power) is white (W).

A good place for the "sense" circuit would be after the ammeter and fuse block.  One of the green (G) wires would be perfect.  Or, as most people do, you can just attach it to the nutted terminal on the alt.  Not ideal, but it works.

* except NY, I know it can be confusing at times but the NY wire is fed un-fused, alt power when the engine is turning.  note "turning" as it can be fed power while the engine spins down after the ignition is shut off.  So it does make a bit of sense after all.

[cazman]

Sorry, bit still not sure what to wire here. I think that the 1 wire alternator might be best to go back to then.

[jbcollier]

One wire alternators were designed for chrome-loving, hot rodders who want everything to be clean and smooth.  They want a no-wires look.  One wire alternators "can" give a lower voltage output if there is any voltage drop in the system.  They also need to be spun faster before they will energize on start-up as the field is not being powered but relies on residual magnetism remaining from the last time it was powered.

If you want an easier install, go with a plain-jane, AC Delco (Delco Remy) 10SI alternator.  They are readily available and easy to wire in.  You can buy a matching pigtail and it is even easier.  Three connections only: warning (NY), sense (to main connection) and the main connection.  I have wired in hundreds of them.

I am currently running a one wire alternator because it was all I could find at the time with sufficient output.  Start up is ok but output is low at low rpms -- decidedly not ok.  I have bought a new, Delco Remy unit with the required output and will be fitting that soon instead.

[Fotog]

I don't know more than JB, I'm sure.  But let me try to explain.  I'm an electrical engineer by training (even if I haven't worked as one in a long time).  I think I understand the situation.  There's always the possibility that I don't though.

The large Brown/white wire:  it provides the output voltage and current to power the system.  It goes from the big terminal with a nut on the alternator to the ammeter.  From the other terminal on the ammeter, a similar sized large brown wire goes to the starter motor and solenoid and on to the battery to keep it charged.  The current simply passes through the ammeter on the way to the starter/solenoid and then the battery, to keep it charged.

The Sense wire:  This one provides a feedback to the voltage regulator inside the alternator, so it can sense how it's doing with respect to controlling the voltage.  No significant current flows in this wire.  It's just 'reading' the voltage remotely for the alternator's voltage regulator.  For my TC, the wiring diagram shows it going to the starter/solenoid.  I would admit that I'm not sure what is the ideal place to sense the output voltage; I've wondered if it is better at the battery, but would do some online reading before I make a change.  John suggests connecting it somewhere after the fuse block.  That could be on the output side of the fuse that's connected to either the white or yellow wire from the ignition switch.  I think for your car to work this isn't really critical, but that would be fine. 

The wire for the charge warning light:  One connection to the light is connected to power, +12v, when the ignition switch is 'on'.  The second connection through this wire provides a path to ground through the alternator to turn the light on if the alternator isn't charging, like when the car hasn't been started.  So it makes sense that it will turn the light on when you turn the key to 'on', but haven't yet started the car.  The connection to ground is broken when the alternator is operating, turning off the light.

The last wire is the one labeled 'ignition'.  That one must be connected to some source of voltage when the ignition is turned on.  It provides voltage to make a magnetic field in the alternator to operate it.  I don't know, but my guess is that in the old days the alternators had permanent magnets, but now they might operate with an electromagnet instead.  So it provides the voltage for that.  I say voltage and not power because it will draw very little current.  It takes very little work to make the magnetic field. That one must be connected to a source of +12v when the ignition is turned on.  So, like JB said, the white wire from the ignition switch (goes to the fuse block too) would be fine for that purpose.

I think it should work fine.  Good Luck!
-Vince

[cazman]

Thanks. All.

I guess why it is confusing is because on the original alternator there is just Ind and Bat+ and those connected to the small NY and NW wires, respectively. The NW is not fused, but Lotus used it to excite the field apparently. The lnd is the lamp. However, there seems to be no sensing wire in the original scheme. Or sensing was done internally?

So - if I upgrade to a 50 amp six pound alternator, add the sensing, the fused switched ignition, upgrade the wire gauge for main ground and battery, then it seems we are far from Lucas!

[Fotog]

Well, I apologize for not reading the manual before posting.  There's a field coil inside the (original) alternator that is energized.... apparently via an internal connection.

I think the only significant difference between this alternator you have and the original is that the connection to energize the field coil is external rather than internal.

The "Bat+" connection is the sense connection, I'm virtually sure.  Cazman, you say that it's connected to a small gauge NW wire.  It should be NP.  The bit of wiring diagram you posted previously showed it as NP, as does the diagram attached below from the manual.

-V

[Fotog]

And if I'm wrong somehow, feel free to straighten me out!

[cazman]

Thanks for finding the picture in the manual. I did not know it was there.

Yes, I think I have the NW and NP mixed. How does this look?

[Fotog]

No, sorry. 

The "Ignition", green wire should go to a source that's switched by the ignition key, like the W (white) wire going to the fuse block from the ignition switch.  That's the wire to energize the field coil in the alternator.  NW connects through the ammeter ultimately to the battery, so it's always energized.  Not what you want.  Even though low power consumption, it would never be turned-off and would drain the battery.

The large terminal with the nut you've labeled NP (brown / purple).  No.  It gets attached to the large Brown wire with white tracer (NW).  That goes to the ammeter, and from the other terminal on the ammeter current flows via large N (Brown) to the starter and to the battery to re-charge it.

NP (Brown w/ purple tracer) 18 gauge connects to the Sense (blue) as you've shown.  That's ok in your picture.  TC wiring diagram shows the NP ultimately connecting to the starter, to sense the voltage there for the regulator operation.

The red connecting to  NY... the indicator light, is also ok.

Here's a brief explanation of remote sensing from Delco: https://www.delcoremy.com/alternators/alternator-features/remote-sense

[cazman]

Good thing I have you. Thanks

[jbcollier]

The thin NW is your remote sense as it provides a voltage reading after the ammeter.  You need either a white feed (coil) or green feed (stop light switch) to power the green wire.

[Fotog]

Ruh roh!  It seems we have disagreement!

JB-  you're my Europa guru.  You know a ton about these cars, and many others.  I have a list of questions that I hope you'll weigh-in on.  But in this case, I don't agree.

I think step one is to determine how the original system works; what connection does what.  Then step 2 is to decide how to apply the new alternator given our understanding of the system.   

I have only been able to find technical information (a schematic) of the original Delco Remy DN460 alternator as part of a Triumph TR6 Shop manual.  It clearly shows the "Bat+" terminal to be a feedback terminal used to operate the internal voltage regulator.  And in the original TC wiring diagram, that is connected to the Brown/purple (NP) wire.  Maybe that wire would best go to the battery (as it appears Delco intended), but Lotus chose the starter terminal, nearby (electrically). 

The NW wires are all power output from the alternator.  The thick one goes through the ammeter to charge the battery, and the thinner one powers the rest of the car's circuits, except running lights and headlamps, via the ignition switch.  The alternator will work if the sense is connected to NW, but one wouldn't be taking advantage of the remote sensing capability.  We really want to control the charging voltage to the battery, right?  That's the most critical thing.  Most everything else gets whatever voltage happens to be there and isn't so critical.  Anything else that is critical, like gauges, gets their supply via a separate voltage regulator ("voltage stabilizer" on the wiring diagram).

I think "after" the ammeter depends upon your reference.  Not sure what that is.  The ammeter is in the middle. On one side is the battery.  On the other is the alternator and all the car circuits (except the hazard flashers).  So the ammeter just tells us if the net current is flowing to the battery, or from the battery to the rest of the car.  It doesn't necessarily look so simple on the wiring diagram.   Relative to the alternator, the battery is "after" the ammeter.

Cazman-  Do you want to post an instruction sheet for your alternator, or at least the Denso part number?

[jbcollier]

Well, he says the NW wire is thin.  That means you are not running 30 amps up that.

Looking at the schematic the NW should be thick, say 12g to 10g and the NP to the starter should be thin as it, in the schematic, is the sense wire to the starter battery connection.  But, he says the NW is thin...

[Fotog]

Yes.  There are two NWs.  One is something like 10Ga and connects between the alternator output and the ammeter.  The other is small, probably 16 Ga and goes to the ignition switch.  From there it powers everything else except for running lights and headlamps (they get their own feed, NU, from the ammeter connection) and the hazard lights.

And yes; the NP is I think 18 Ga.

I sure hope he can hook this thing up now.  It shouldn't be too difficult.