TR2/3/3A Help wiring convertion alternator

[Lukens]

Now that I've finished with the mechanical stuff, I need help with the wiring.
I bought a Nippon Denso unit and the supplier converted it to "one wire". There are plenty of post that show how to wire a "three wire" alternator, but I've found nothing on a one wire. I must confess that I know nothing about what goes on in the generator control box ( I intend to abandon).
Take a look at my proposed wiring and tell me if it's correct. (I'll add some more fuses and circuits later). Notice I haven't located the ammeter or warning light.
Would I be better off to rewire my alt to a three wire set-up?

<img class="previewthumb" id="vbattach_37152" alt="" src="https://www.britishcarforum.com/bcf/attachment.php?attachmentid=37152&stc=1" attachmentid="37152">

 

[TR3driver]

Er, I don't see an alternator in that diagram. If the alternator is truly a "one wire" setup, then it won't operate the warning light. But sometimes when they say "one wire", they only mean it can work without the light and the light can remain functional.

What you have in your diagram would work, but has several major changes from stock, which might not be a good idea.
Personally, I would not want the starter button active all the time, since I know that, sooner or later, I'll wind up trying to start the engine without turning the key on. And I don't recall ever wishing it was the other way around.
Running the headlight current through the ignition switch seems like a bad idea to me. Possibly my original switch was just old and tired, but it started getting warm with only about 12 amps or so going through it. And if you're running tungsten or halogen headlights, you want to get all the voltage to them that you can (for more light).

FWIW though, I have wished several times that the brake lights worked with the key off, so that's the way my TR3 is wired. Not such a big deal now that the cooling problems are over, but back when I was having cooling problems, I would frequently coast with the engine off. Probably good to still have brake lights then.

You won't need the generator control box, so deleting it is fine.

 

[Lukens]

Thanks for your input Randall.
Oops, the alternator would be a good idea. Where would I put the ammeter? Between the alt and battery?
As far as the starter being live, it makes setting the valves easy... bumping the solenoid. I've tried turning the crank by the fan, but that's a pain... literally.

 

[TR3driver]

You're not using the stock TR3 solenoid? The button on the back of it works all the time.

Yes, the ammeter goes between the alternator and battery.

But if you are using an alternator that is rated for more than 40 amps or so, and the stock 30 amp ammeter, you might want to consider using a shunt so the ammeter doesn't hit the peg. When I initially installed a 60 amp Ford alternator "back when", the ammeter started sticking after just a few days, which I took to mean it didn't like having the needle whacking against the peg on every start up.

 

[HAWAIICJ]

I installed a Nippon Denso alt out of a 95 Corolla on my TR4 and the wiring was fairly simple. I did however omit the ammeter and replaced it with a voltmeter. I wired the alt with the 3 signal control wires, ignition, battery voltage and charge light.

How was the alternator converted? I found this pdf showing internal modifications - https://www.google.com/url?sa=t&rct...zpm93TOuBs1FFpo9V6c-RWg&bvm=bv.92291466,d.eXY

In your diagram the ammeter would go between the battery and ign switch and you may need to install a shunt depending on the electrical loads. Are you planning to run the alternator high current output directly to the battery? That is how I did it with a #8 wire to the starter solenoid.

Is your starter button powered with the ignition off that is how you show it wired? Do you plan on rewiring the car?

The one wire alternator has only the High current wire to the solenoid and is self exciting.

I found this online:1-Wire Explained


A 1-wire alternator, also known as a self-exciting alternator, is commonly used on custom cars & trucks, tractors and other non standard applications when simplified wiring is a factor. As the name implies, these alternators provide only one wire connection: the BATT terminal. A heavy cable is typically run directly from the BATT terminal to the positive terminal of the battery.

1-wire alternators are essentially 3-wire setups that have been rewired internally for a simplified final installation:
•No Remote Voltage Sense Input:
The regulator's sense line is still used, but instead of connecting to a remote location in your car, it is simply routed directly to the output feed of the regulator. This connection may be inside the alternator where it would be completely hidden from view, or the sense line may actually have an external terminal attached to the output feed stud on the back side of the alternator (see photo above).


A common complaint among custom street rod owners using the 1-wire setup is that their headlights are dim, even with a huge 100-amp alternator wired directly to the battery. This is due to the lack of remote voltage sensing at the power distribution point.

•No Field Excite/Warning Light Indicator Input:
The ignition warning light indicator function is omitted with a 1-wire alternator, so your idiot light will not be operational with this setup.

For the 1-wire, self-exciting design, the field windings are not energized via the ignition switch; instead, a special circuit is built into the internal voltage regulator that senses the rotation of the alternator’s rotor. The rotor must turn at sufficient speed to trip the circuit which excites the field windings and starts the charging process. This “cut-in” speed is affected by several things and is typically higher with certain high amperage alternators. Prior to reaching the cut-in speed, the charging system is not activated and the battery will be discharging. However, once the cut-in circuit is tripped, the alternator will charge at all speeds, even very low ones, until the alternator’s rotor comes to a complete stop. At that point, the circuit will shut off and wait for the process to be repeated.

Typically, after starting the engine, the engine must be revved above 1200-2000 RPM to turn-on the 1-wire alternator.



The advantage of a 1-wire system over the 3-wire system is that the installation is simplified and provides for a very clean installation. All that is required is a heavy gauge cable running between the output feed stud on the rear of the alternator and the battery.

Some of the disadvantages associated with the 1-wire system are:
•Less than optimal voltage levels at points downstream from the alternator;
•The ignition warning light is omitted;
•At startup, a slow-running engine will not be spinning fast enough to turn-on the alternator and the system will be discharging until the throttle is blipped and the engine revs higher than the alternator cut-in speed.
•Higher cost than 3-wire equivalent.

Summary:

3-Wire Alternator:

Advantages
•Ignition warning light works as designed.
•Field windings turn on with ignition switch (no cut-in required).
•Much better voltage regulation at the main terminal power post.
•Inexpensive and plentiful.

Disadvantages
•A little more complicated to wire up.


1-Wire Alternator:

Advantages
•Installation is simplified and provides for a very clean setup.

Disadvantages
•Regulated voltage monitored at alternator; low voltage conditions may occur at main terminal power post.
•The ignition warning light is omitted
•Throttle must be blipped 1200-2000 RPM at startup to force it to cut-in.
•More expensive to buy.

 

[HAWAIICJ]

While I was researching Tr3 and one wire alt, Randall got it!

 

[TR3driver]

Typically, after starting the engine, the engine must be revved above 1200-2000 RPM to turn-on the 1-wire alternator.

This may vary from setup to setup, depending on the alternator and pulley size used. With my old Ford Motorcraft alternator and an original generator pulley (somewhat larger than optimal but readily available and compatible with the original belt), it took some 4000 rpm to get it going without any current from the dash lamp.

Even with the stock dash lamp, it took some 2500 or so. So I added a resistor under the dash to pass a little more current and get it started at idle rpm.