The Fordson Tractor Pages Forum

Just renewing some of the birds nest that passes for wiring on the power major and have a question or two.

The starter circuit is simple enough, basically, a 12v feed from bolt 1 on the solenoid goes to the switch on top of the starter, which when made, activates the solenoid and sends current to the starter from bolt 2.

The Alternator has two wires. and as it is at present, has a thicker wire connected to bolt 1 on the solenoid and a thinner wire going first to the ignition switch, then to a bulb when the ignition is 'on' and then to the same place as the thicker wire, bolt 1 of the solenoid.

This does not sound right to me.

Don't ask for wire colours as they are mostly all the same.

Anyone have any thoughts??

Thanks.

That is right if you have an alternator. That is the "exciter" circuit which is used initially to feed the internal magnet. Once the alternator is charging, this circuit switches off and the regulator takes over, varying the magnetic field to the load on the alternator.

http://i407.photobucket.com/albums/pp15 ... ctric2.jpg

Is the regulator built in to the alternator? Because the solenoid is the only electrical 'lump' I can see. And what would be the point of the alternator / lamp connection being switched via the ignition switch??? I would have thought it made more sense to put the ignition switch in the starter circuit.

Yes if it is a Lucas. Some other alternators have external regulators. The feed for your starter switch also should go via the ignition switch but it is not in the same circuit as the alternator wire.

Most alternators these days have built in regulators. It is wired in with the ignition switch otherwise the "no charge" warning light on the dash would be illuminated all the time the tractor wasn't running and you would have a flat battery!

You can determine whether or not an alternator has internal or a separate regulator by the model designation. A 4AC, 14AC, 17AC etc. has a separate reg, whilst a 4ACR, 14ACR, 17ACR etc. has an inbuilt one - with the R standing for internal Regulator.
Like most things in life you don't get something for nothing -- and alternators are no exception. Turning the ignition on supplies a current to the alternator field windings and the red, or whatever, lights up. Only when the rotor starts spinning does it convert that initial ignition 12v. supply to about 13 or 14v. and the rated amps of the unit. As long as the back voltage flow from this equales the ignition switch volts there is no volt flow in the ignition circuit, so the red light goes out.
In general a 5amp. wire is good enough for the ignition switch circuit, with a 50amp. one for the alternator to battery one [provided the output is less than 50amps].
Pavel

This may sound like a silly question, but can the alternator circuit and the starter circuit both run through the same contacts on the ignition switch?

Answer; Yes.
A single wire from the ignition switch to the starter solenoid can also continue to the indicator/inciter terminal on the alternator.
There is no 'start' position on the ignition switch which, the motor having started, returns to 'run' as in later vehicles. The starter solenoid only becomes active when you press down on the start lever. There may well be a slight delay, but as soon as the motor starts and the lever is released, full 12 plus volts go to the alternator and alternator output commences.
This is how mine is wired -- it saves an extra wire run.
Pavel.

Halloween, re my post above.
As I stated, wiring the alternator terminal direct from the starter solenoid is how I wired mine. However, I've just remembered that I also relocated the solenoid wire connection on the ignition switch so that the key had to be in the ON position to make the solenoid wire live.
I believe that on the original Fordson wiring this wire was permanently alive and that would cause serious trouble to the alternator.
Sorry about that; as it was about 5 years ago when I re-wired mine the memory had obviously dimmed.