[AT] ford N charging system

[Chris Britton]

Sorry John.. not completely correct.

Ford N series that used the 2 brush non adjustable genny was INDEED "A" 
Circuit type.  This genny DID rely upon an externally grounded to provide 
charge.  That is, one side of the field coil was hooked to the armature 
internally, and the other side terminated at the insulated field lug on the 
genny case.  The regulator used a vibrating contact with applied ground to 
the field terminal ( there was also a field bias resistor between ground and 
the field terminal on the regulator to provide some needle bounce buffering 
by keeping a bit of field current going even when the contacts were open.

Jump ahead to 53 and the NAA, and ford went to the "B" Circuit systems that 
needed power to the field lug to charge.  in those systems, the field coil 
was internally grounded to the case, and the other side of the coil went to 
the insulated field lug on the genny case.  The regulator applied field 
power to the field terminal via the vibrating field contact. You could also 
have a bias resistor between the field lug and the armature lug  on the 
regulator, plus another bias resistor, depending on design of the 
regulator.. etc.

Applying power to the field terminal on a A-Circuit system is a GREAT way to 
burn up a 40$ regulator.

Testing:

A-circuit

Try to motor it, pull all wires off genny, slip belt off, apply battery 
power to the armature, ground the field.
Genny should motor.  If not, check brushes and coils.  May need a growler or 
a shop to do this. Most gennies that motor, will charge.  Most gennies that 
charge, will motor.

B-Circuit

motoring, remove all wires from genny, slip belt off, jumper power to 
armature, jumper power to field.  genyy should motor.


Polarizing correctly:

Hook up all wires and the regulator as per oem wire diagram.  have a good 
charged battery installed to the correct polarity:

A-Circuit

Engine off, Jumper battery to armature.  This can be at the regulator or 
with a piece of wire from bat hot to armature lug.. electrically it's all 
the same.  You should see a spark.

B-Circuit

Engine off, Jumper Battery hot to field,


FULL FIELD test:

A-Circuit

Engine running, 1000rpm or so.. Ground field tab at genny, look at ammeter.. 
should put out 10-20+amps.. don't do this very long.

B-Circuit

engine running, 1000 rpm or so, jumper power to field tab at genny, observe 
ammeter, should get 10-20+ amp reading.
(yes, this is the same as the Bcircuit polarization procedure.. )


Ford continued the B circuit design up thru the thousand series.  Lucas 
systems are also B circuit.

Early 3 brush gennies on the 9n/2n with a cutout only:

polarize by jumpering around cutout relay.. ie, jumper the 2 terminals on 
the relay.

motor test by slipping belt off, jumper power to the armature, adjust 3rd 
brush to max

Soundguy


>From: John Wilkens <jwilkens at eoni.com>
>Subject: Re: [AT] Ford N tractor
>Good luck Richard!  I've been fooling with charging systems for years
>and I still can't get it right.  One thing to remember is that,
>unlike GM stuff where you ground the field to make juice, with the
>old fords you need to apply power to the field terminal to make it
>>charge.  Keep us posted.   John W.    (I hope this doesn't start a
>string like my "grounded coil" question!)