3 wire to 1 wire alternator

[cazman]

I just switched to a modern alternator that is one wire (I tried to find a compatible 3 wire, but no luck).

I assumed that I just left the two small wires that used to go to the old connectors (for dash light and battery) off and the big brown to the alt post and the other large brown to ground. No start.

I looked through the posts, but could find help for converting. Does anyone know?

[Grumblebuns]

Check the Knowledgebase:

https://www.prevanders.net/kb2.html

type in "alternator", there are about 1K replies on the subject including alternate alternators

[cazman]

I have read most of of those and others. No one really says to not connect the other small wires to anything for a 1 wire alt. I guess that is what is done, so I must have another problem.

[BDA]

This got me curious and I found this article (https://www.streetmusclemag.com/tech-stories/electronics-efi/one-wire-alternators-are-they-better-or-just-easier-to-hook-up/). It might be useful.

[jbcollier]

If you still have the stock wiring, brown is battery positive, not ground.

[cazman]

Its working. It was a ground wire that loosened.

On mine I have two large brown wires, one for ground and one for battery. Then the two smaller ones.

I was just trying to discern if there wasn't something special about the Europa wiring that required the smaller ones to be wired somewhere. In all the posts, I have not found anyone saying anything about them. I taped them off and but them back into my wire loom.

Even though I wanted a three wire alternator, I got a one wire now. I guess they can promote parasitic drain, I hope not.

[dakazman]

  Glad to hear it worked out for you cazman. I didn’t chime in because I have yet to run mine on a Renault. The mounts and brackets were also changed on wedge motor and will also work on a cross flow.  These alternators are also unidirectional.
What mfg , and part number did you use ?
 BDA , the tuff stuff is the alternator I will be running… soon hopefully.
Dakazman

[cazman]

Here is what I bought. Although, I do not know if I would recommend this company. They did not seem to know which of their products were 1 wire or 3 wire.

https://www.dbelectrical.com/products/alternator-for-universal-race-car-8172-8162-28162-pwm8172-6666-dui6666.html

I had to make a new bracket.

[RonPNW]

If you have original wiring the wire size is too small for this alternator (it was also too small for the stock alternator). I ended up getting rid of the amp meter (replaced it with an A/F meter) and went to 4 gauge wire. One directly to the battery the other directly to a relay that supplied the radiator fan. You can just use an idiot light for alternator status (one of the small wires does this) You will have a faster fan and brighter lights if you do this. Don't forget to beef up all the ground wires.

Ron

[cazman]

Do you think a 3 wire 50 amp would be more appropriate? That was my original choice.

[cazman]

So, I bought a Denso 3 wire alternator and I am back to figuring our what to do with the wires.

On the one wire, I am clear that you just leave the two small leads alone and never use them.

On the Denso 3 wire, there are three connections other than the large main battery wire. So, I am left with one connection extra. I have already hooked it up with the one of the small wires (the one that is always hot) going to the Sense lead. The other (the one that is switched power) going to the Ignition lead. It seems to work, but I am left with the Light lead on the alternator. And my dash light does not go on at all with the key in run.

Any advice?

[jbcollier]

The nutted terminal takes the fat battery feed

Red goes to an ignition fed warning light

Blue goes to battery wherever you want for system voltage referenced to (I often run it to the fat battery feed

Green goes to ignition

[cazman]

Yup. that's what the picture I attached says.

Still not enough wires. Why does the stock alternator only have two connectors for these three functions?

[jbcollier]

Because it has a separate regulator.

The alternator you have bought has quite a few wires to hook up.  Some only have three for the same functions.  It's all down to design decisions.  In modern cars, alt loads are high and voltage drop can be an issue.  Having a remote sense wire resolves that issue.

[Fotog]

There's no separate regulator in a twin-cam.  The wiring diagram shows only 3 wires including the large primary wire to the battery.  The original Delco also has a sense connection.  What does the "ignition" wire do?

Google search tells me that "the fourth wire provides power to the field coil, which creates the magnetic field to generate electricity."  which seems like a pretty good explanation.  Not sure why it's now different than 'back in the day', but I understand:  you turn on the ignition, it provides power to the alternator; it does its thing.  Voila!