Farmall Super A wiring issue

HVFDfirefighter · Aug 10, 2017

1952 Farmall Super A: Ok, I took all old wires off and replaced them according to a three wire alternator. It is a 12 volt negative ground. Problem was I could not get the tractor to shut off. I wired in a light from the number 1 wire from alternator but it still would not shut off. So I rewired using the following diagram using only one wire from alternator. Now tractor runs and shuts off as it should. When running, the ammeter is showing a positive charge. My question is: can this setup boil my battery? I figure the alternator has a voltage regulator in it and uses the three wires. Since I am only using one wire, does it skip the regulator? If so, how does it know when to charge and when not to charge? I do not have any of the lights hooked up yet.

Any help is always appreciated

old · Aug 10, 2017

If it is a true 3 wire all the wires need to be hooked up to work as it should and if you did not switch the wires around on the Amp gauge it is not charging . The #1 wire is the excite wire and if you use the wrong type light bulb it will not shut down if wired correctly. One can use a simple ballast resister like the VR-1 from O'Reilly's auto parts store in place of the light bulb. The #2 wire it the sense wire and that tells the V.R. what the battery is doing

Steve@Advance · Aug 10, 2017

I suspect someone put a "one wire" alternator on.

Seems I remember you saying the harness plug was taped over, that's probably why.

With a one wire, the regulator takes care of everything, or should. You can put a volt meter across the battery, with it revved up you should get about 14.6 volts.

If it's not a one wire, it won't charge without the harness plug connected.

Janicholson · Aug 10, 2017

THe light bulb needed to be connected so that the terminals on the light bulb were not connected to ground. This means that one of
the connections goes to the ignition from the on off switch, and the other goes to the #1 terminal. The light bulb (small one)
will have enough internal resistance to disallow running. (about 10 ohms) A 10 ohm plain old resistor will also work, as will a
small diode set to keep voltage from getting to the ignition, but allowing voltage to get from the ignition to the alt#1 terminal.
It for sure needs the connection to the #2 terminal to remind it of the output voltage. A second resistor (as pointed out by old)
can also work if it drops the voltage enough to stop the ignition from firing. If it has a ballast resistor already in the
ignition circuit, the added ohms will be about 5. Jim

HVFDfirefighter · Aug 10, 2017

THe light bulb needed to be connected so that the terminals on the light bulb were not connected to ground. This means that one of the connections goes to the ignition from the on off switch, and the other goes to the #1 terminal. [/quote]
That must have been the problem. I had connected the #1 wire from alternator to terminal on light and a short jumper from the same terminal on light to the ignition. I connected the coil wire to the same side of the ignition as the jumper from light. (Duh,
Competing the circuit for the coil) The other side of light was running to negative ground. The other side of ignition was hooked to ammeter.

So the light does not need a ground? #1 in on one side of light, #1 out on other side of light to ignition. Coil wire on same terminal as #1 on ignition and other side of ignition to ammeter.

Question: I am currently only using the "B" wire from alternator and the tractor is running and shutting off as it should. Which is the better setup: one wire or three wires from alternator?

Steve@Advance · Aug 10, 2017

If it's charging with only the BAT wire connected, it has to have a one wire regulator in it.

I don't know what it will do if you connect the wires, probably work as it is, but give you a charge
indicator light.

The advantage of the one wire is easy to connect, just one wire.

The disadvantage, sometimes they need to be revved higher than a 3 wire to start charging. Some believe the
one wire set up causes a small battery drain. If they do, it is minuscule, would take months to be
noticable.

old · Aug 10, 2017

Lets make this so simple a cave man can do it. The #1 wire from the alternator hooks to one side of the light bulb and the other wire from the light bulb goes to the ignition side of the ignition switch or to save wire to the ignition side of the coil. Or in other word the light bulb is wire to be part of the #1 wire

Janicholson · Aug 10, 2017

Many Delco alternators will charge with no signal on terminal 1. They usually need to be operated rather fast to start charging , but do work. The #2 terminal really needs to be attached to the B (big stud) terminal to adequately control charging voltage.

HVFDfirefighter · Aug 11, 2017

(quoted from post at 19:40:29 08/10/17) Many Delco alternators will charge with no signal on terminal 1. They usually need to be operated rather fast to start charging , but do work. The #2 terminal really needs to be attached to the B (big stud) terminal to adequately control charging voltage.

So can I operate alternator with just the B to ammeter with a short jumper from the #2 to the B? (#1 not used at all)

I have tractor set up now with just the B. Ammeter is showing a positive charge. I have not checked the volts yet at the battery.

Farmall Super A wiring issue

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