Charging System trouble

I have a Ford 8n that I am having issues with. A couple years ago, I had the generator fixed and Voltage regulator replaced. IT charged well for a while then stopped working. The other day I did a test from the book and grounded the field. The ammeter started showing charging well immediately. So I replaced the regulator and repolarized arm to bat terminals. Started the tractor and the ammeter showed no charge but the multimeter on the battery showed a charge bouncing from 6.65 v to 7.20 volts then a short half second jump to like 16 volts which made no sense. Then the battery started showing 6.29 to 6.40. I then disconnected everything and tested the generator and it spun well. What is going on here does anyone have any ideas? I am completely baffled.

No expert, but what I understand it is best to disconnect the field wire from the regulator before polarizing a Ford generator.

You may have arced the field points in the regulator.

When you say multi meter, are you using a digital or analog? Digital meters don't like dirty signals the old regulators produce. It can jump all over the place, meaning nothing. An analog meter is better suited for your application.

If you think the regulator was damaged, try opening it up and filing the field contacts. Takes a special thin points file, don't sand them!

That is just part of the maintenance on regulators, they need the field contacts dressed occasionally. The new after market regulators are especially bad about the points needing dressing. The alloys they use are not the same quality as years gone by. If you have any old regulators you might can save them.

(quoted from post at 11:33:34 02/10/22) No expert, but what I understand it is best to disconnect the field wire from the regulator before polarizing a Ford generator.

You may have arced the field points in the regulator.

When you say multi meter, are you using a digital or analog? Digital meters don't like dirty signals the old regulators produce. It can jump all over the place, meaning nothing. An analog meter is better suited for your application.

If you think the regulator was damaged, try opening it up and filing the field contacts. Takes a special thin points file, don't sand them!

That is just part of the maintenance on regulators, they need the field contacts dressed occasionally. The new after market regulators are especially bad about the points needing dressing. The alloys they use are not the same quality as years gone by. If you have any old regulators you might can save them.

Click to expand...

"I understand it is best to disconnect the field wire from the regulator before polarizing a Ford generator.

You may have arced the field points in the regulator. "

Steve, the "N" Fords used an "A circuit" generator vs. the "B circuit" system you are giving advice about (that Ford commonly used over the years, the N's are an exception).

That ground the field test (aka full field) is intended for Class A charging circuits. On the Class B you full field by applying voltage
to the FLD post, NOT by grounding it. (Class B has the field windings internally grounded then out to the external FLD post)

When I polarize a Class B system I momentarily flash jump from BAT to FLD unlike a Class A when I jump from BAT to ARM.

If you work your way through my Troubleshooting Procedure linked below it can help find the cause of non charging for Class A Charging
Systems (Its NOT for Class B). Its ground the field test and Motor Test (pars 5) can tell if the problem is a Generator or a Voltage
Regulator.

On the Class A if it charges fine ONLY with the FLD grounded but NOT otherwise, the genny itself is okay so the problem is either a bad
bad VR orrrrrrrrrrr the VR isnt well grounded

INSURE BOTH THE GENNY AND VR HAVE GOOD GROUNDS Try my Troubleshooting Procedure for a Class A system

https://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=ttalk&th=2060825

John T
John Ts Charging Troubleshooting Class A

Are you using a digital volt meter to measure charging voltage. It is not unusual to see erratic voltage readings with a digital meter when around ignition or charging systems.

Try an analog meter if you have one.

I apologize in advance for getting away from original posters exact topic, but it has slipped into how to polarize Class A vs class B already, so here is a question. Why polarize them differently, other than "that is the way someone said do" it or "that is the way it has always been done"? I see no reason that both A & B can not both be successfully polarized bat momentarily connecting BATT to ARM, with all connections remaining in place.

So how do I know if my tractor has a class A or B charging system?

(quoted from post at 17:56:12 02/10/22)
So how do I know if my tractor has a class A or B charging system?

Click to expand...

As I stated in my previous reply, the "N" series used "A" circuit generators.

Unless yours has had a different type of generator swapped on over the years you (obviously) are dealing with an "A circuit" charging system.

With no wires connected to it, an "A circuit" generator will have continuity between it's "F" terminal and "A" terminal, a "B circuit" generator will have continuity between it's "F" terminal and it's "frame".

Your last question


So how do I know if my tractor has a class A or B charging system?

If it's a Class B, inside the genny one end of the Field (two sides in series) is grounded and other end goes out to the FLD Post

If its a Class A two brush one end of Field is wired to or same as the ARM post and the other end (of two sides in series) goes out to the
FLD post

If its a Class B you apply regulated voltage to the FLD post to control rate of charge

If its a Class A you apply a regulated (straight or resistive and controlled/regulated by VR) GROUND to the FLD post to control rate of
charge

If it charges fine if you dead ground the field (full fielding) but not otherwise its likely a Class A. If it charges fine if you apply
voltage to the FLD (full fielding) its likely a Class B.

TROUBLE IS when I was a used tractor dealer I saw so many tractors charging systems CHANGED MODIFIED OR JURY RIGGED so just because a
tractor was original Class A (such as some Fords) doesnt prove it still is so reading the above may show what yours is HOWEVER if it
charges good with FLD dead grounded that tells me ITS A CLASS A.

Again a dead ground on FLD making her charge good sounds like an A while applying voltage to FLD making her charge sounds like a B

Does this answer your question ?? any more questions??

If its a Class A try my Troubleshooting Procedure to help find the problem. Make sure BOTH the VR and Genny have good grounds, try a
grounding jumper.......My Motor test (Para 5) and full fielding test (dead ground FLD post) can tell if the genny itself is okay and
therefore the VR or its bad ground may be the problem

John T
John Ts Charging Troubleshooting

Ok. That makes sense. Seeing how it is a brand new regulator I will try grounding the field and polarizing it again. Should I do that while the tractor is running?
I did test the generator and it spins well. This is a class A still because it shows charge when grounding the field.

I have ran across you trouble shooting sheet before. Very helpful place to learn how to fix them things. No where can you find information about them it seems.
Thank you!

(quoted from post at 10:00:19 02/11/22) Ok. That makes sense. Seeing how it is a brand new regulator I will try grounding the field and polarizing it again. Should I do that while the tractor is running?
I did test the generator and it spins well. This is a class A still because it shows charge when grounding the field.

I have ran across you trouble shooting sheet before. Very helpful place to learn how to fix them things. No where can you find information about them it seems.
Thank you!

Click to expand...

This is a class A still because it shows charge when grounding the field" Well, my friend, if that is the case, it is polarized just fine as it stands.....do not more polarizing.

(quoted from post at 10:00:19 02/11/22) Ok. That makes sense. Seeing how it is a brand new regulator I will try grounding the field and polarizing it again. Should I do that while the tractor is running? !

Click to expand...

No, polarizing is done with the tractor and ignition off.
Don't rule out a faulty brand new 6 volt regulator. As a matter of fact, good luck in trying to get a good one. I gave up and now convert to 12 volt alternator when 6 volt regulators fail.

You Polarize BEFORE start up......Then when running at fast RPM if she fails to charge when needed UNLESS YOU GROUND THE FIELD AND IT CHARGES THEN (says the genny itself is okay) the VR is bad or not well grounded.

Youre welcome glad to help thanks for the kind words

John T

(quoted from post at 12:00:27 02/11/22)

(quoted from post at 10:00:19 02/11/22) Ok. That makes sense. Seeing how it is a brand new regulator I will try grounding the field and polarizing it again. Should I do that while the tractor is running? !

Click to expand...

No, polarizing is done with the tractor and ignition off.
Don't rule out a faulty brand new 6 volt regulator. As a matter of fact, good luck in trying to get a good one. I gave up and now convert to 12 volt alternator when 6 volt regulators fail.

Click to expand...

The second faulty 6V regulator is the reason my 860 now has an alternator.
Now I have a good 6 volt generator lying on the floor.

I hate to bother again but I really am at a wall. So I hooked everything up and polarized by grounding the field and then jumping bat to arm. I started the tractor and still showed a discharge. Next I did the test and ran a wire from the field to ground and nothing changed. with the regulator was a piece of paper and it was talking about testing the voltage regulator. It suggested to jump from Arm to Bat and if it charged the vr was bad. I did that and it showed heavy discharge. Next it suggested running Arm to FLD and if charged vr was bad.I did that and showed no change. Im really baffled with what is wrong. my Gen did the motor test well so Ik that's working It all brand new wiring and the ammeter is also new. The voltage regulator I put on was one Grandpa had bought a while ago and it is a Wells VR613