Model H Electrical Puzzle

Eugene Johnson · Dec 2, 2021

I installed a new wiring harness on 1947 Model H. With engine running the ammeter shows charging. With engine not running and lights ON ammeter shows reasonable discharge. However with lights and engine both ON the ammeter pegs erratically at the discharge limit which I assume is a bad thing.

Background: Battery is changed from original to negative ground.
The light switch is two terminal On-Off - no third terminal or resistor. From appearance I assume the small 2 terminal unit near the generator is a relay - not a regulator.
In absence of a original harness or a diagram with this mix of components I attached the field wire to the load side of the light switch - not sure if this was correct. I should note that the components have been repainted -and may affect grounding if that is required
Puzzle: It worked fine for many years why not now - Parade night is Sat Dec4. Suggestions??
Gene

electro · Dec 2, 2021

Did you change to 12 volt neg ground or 6 volt neg ground? Did you polarize the generator for neg ground? Is the generator an "A" circuit or "B" circuit?

I assume you switched to 12 volt neg ground. You will also need a 12 volt relay or cutout otherwise the generator can cause a large drain which would also happen if the generator was not polarized correctly. I am assuming you have a common "A" circuit generator like would have been the original type. If so, do not hook the field wire to the load or hot side of the light switch. That will not work for an "A" circuit generator although it will work to some extent for a "B" circuit. You need either the correct multi-position light switch or a two charge regulator, a fixed single charge cutout, or a standard regulator, all of the proper voltage for your battery.

My JD H is a hand start with no fancy electric stuff but I believe it originally have had a 3 brush , 6 volt, "A" circuit generator with a multi-position light switch for controlling the output and a 6 volt cutout only.

The key questions would be:

Is it now 12 volt neg ground?
Did you polarize the generator for neg ground?
Did you switch the relay or cutout to 12 volts or use a universal cutout?

I would not hook the field wire to the light switch load terminal.

Eugene Johnson · Dec 2, 2021

(quoted from post at 09:52:21 12/02/21) Did you change to 12 volt neg ground or 6 volt neg ground? Did you polarize the generator for neg ground? Is the generator an "A" circuit or "B" circuit?

I assume you switched to 12 volt neg ground. You will also need a 12 volt relay or cutout otherwise the generator can cause a large drain which would also happen if the generator was not polarized correctly. I am assuming you have a common "A" circuit generator like would have been the original type. If so, do not hook the field wire to the load or hot side of the light switch. That will not work for an "A" circuit generator although it will work to some extent for a "B" circuit. You need either the correct multi-position light switch or a two charge regulator, a fixed single charge cutout, or a standard regulator, all of the proper voltage for your battery.

My JD H is a hand start with no fancy electric stuff but I believe it originally have had a 3 brush , 6 volt, "A" circuit generator with a multi-position light switch for controlling the output and a 6 volt cutout only.

The key questions would be:

Is it now 12 volt neg ground?
Did you polarize the generator for neg ground?
Did you switch the relay or cutout to 12 volts or use a universal cutout?

I would not hook the field wire to the light switch load terminal.

Thank you for the guidance:
It is wired as a 6 volt neg ground.
I did not polarize - will now
I believe the cutout is original -m 6 volt
ps: When I say load side I meant I attached the field wire to the "lights" side of the on/off switch that would not be continuously hot.
Best regards,
Gene

wore out · Dec 2, 2021

(quoted from post at 10:23:24 12/02/21)

(quoted from post at 09:52:21 12/02/21) Did you change to 12 volt neg ground or 6 volt neg ground? Did you polarize the generator for neg ground? Is the generator an "A" circuit or "B" circuit?

I assume you switched to 12 volt neg ground. You will also need a 12 volt relay or cutout otherwise the generator can cause a large drain which would also happen if the generator was not polarized correctly. I am assuming you have a common "A" circuit generator like would have been the original type. If so, do not hook the field wire to the load or hot side of the light switch. That will not work for an "A" circuit generator although it will work to some extent for a "B" circuit. You need either the correct multi-position light switch or a two charge regulator, a fixed single charge cutout, or a standard regulator, all of the proper voltage for your battery.

My JD H is a hand start with no fancy electric stuff but I believe it originally have had a 3 brush , 6 volt, "A" circuit generator with a multi-position light switch for controlling the output and a 6 volt cutout only.

The key questions would be:

Is it now 12 volt neg ground?
Did you polarize the generator for neg ground?
Did you switch the relay or cutout to 12 volts or use a universal cutout?

I would not hook the field wire to the light switch load terminal.

Click to expand...

Thank you for the guidance:
It is wired as a 6 volt neg ground.
I did not polarize - will now
I believe the cutout is original -m 6 volt
ps: When I say load side I meant I attached the field wire to the "lights" side of the on/off switch that would not be continuously hot.
Best regards,
Gene

Since it is charging with the lights not switched "ON" the generator is working and polarizing it is NOT needed.

The issue is that you do not have the correct light switch with a dedicated "FIELD" terminal and have erroneously connected the "FIELD" wire from the generator to the "LOAD" terminal of the light switch.

Get the field wire off of the "LOAD" terminal before you burn out the generator, and install the correct type of light switch with a field resistor and "FIELD" terminal on it!

Current style of AF687R light switch with generator field resistor.

John T · Dec 2, 2021

If you have a simple two terminal (BAT GEN) Cutout Relay versus a full fledged Voltage Regulator (BAT FLD GEN/ARM), the Gennys FLD post
requires a ground to charge which it gets via a Combination Manual Low High Charge Control and Light Switch THATS NOT A LIGHT ONLY SWITCH
!!!!!!

The Cutout Relay (or a VR for that matter) should match your generator, be it 6 or 12 Volt. It can still work at Pos or Neg Ground

You stated I attached the field wire to the load side of the light switch

WRONG for a cutout relay NON VR system the FLD attaches to a Manual Low/High Combination Light and Charge control switch where it gets a
direct ground for HIGH charge but a resistive ground for LOW charge.

It may be getting a ground where you incorrectly wired it ??? which is why it's possible to charge even if thats not correct

Heres my advice

1) Go to johnnypopper.com to get an H Wiring Diagram
2) If you haven't already, get a Cutout Relay that matches your new Generator
3) Get the correct Combination Manual Low/High Light and Charge Control Switch to match your Generator
NOTE it needs a good ground to work
4) Wire it correctly with the Gennys FLD post wired to the FLD terminal on the Low/High switch NOT load side of a normal light switch
5) To be safe just in case Polarize the Generator

YOUR SWITCH AND CUTOUT RELAY NEEDS TO BE CORRECT AND IT MUST BE WIRED RIGHT IE Gennys FLD to the Field control terminal on a correct
combination light and charge control switch NOTTTTTTTT to the light switch portion

Hope this helps

John T
Two Cylinder Wiring Diagrams

Eugene Johnson · Dec 2, 2021

(quoted from post at 10:44:20 12/02/21)

(quoted from post at 10:23:24 12/02/21)

(quoted from post at 09:52:21 12/02/21) Did you change to 12 volt neg ground or 6 volt neg ground? Did you polarize the generator for neg ground? Is the generator an "A" circuit or "B" circuit?

I assume you switched to 12 volt neg ground. You will also need a 12 volt relay or cutout otherwise the generator can cause a large drain which would also happen if the generator was not polarized correctly. I am assuming you have a common "A" circuit generator like would have been the original type. If so, do not hook the field wire to the load or hot side of the light switch. That will not work for an "A" circuit generator although it will work to some extent for a "B" circuit. You need either the correct multi-position light switch or a two charge regulator, a fixed single charge cutout, or a standard regulator, all of the proper voltage for your battery.

My JD H is a hand start with no fancy electric stuff but I believe it originally have had a 3 brush , 6 volt, "A" circuit generator with a multi-position light switch for controlling the output and a 6 volt cutout only.

The key questions would be:

Is it now 12 volt neg ground?
Did you polarize the generator for neg ground?
Did you switch the relay or cutout to 12 volts or use a universal cutout?

I would not hook the field wire to the light switch load terminal.

Click to expand...

Thank you for the guidance:
It is wired as a 6 volt neg ground.
I did not polarize - will now
I believe the cutout is original -m 6 volt
ps: When I say load side I meant I attached the field wire to the "lights" side of the on/off switch that would not be continuously hot.
Best regards,
Gene

Click to expand...

Since it is charging with the lights not switched "ON" the generator is working and polarizing it is NOT needed.

The issue is that you do not have the correct light switch with a dedicated "FIELD" terminal and have erroneously connected the "FIELD" wire from the generator to the "LOAD" terminal of the light switch.

Get the field wire off of the "LOAD" terminal before you burn out the generator, and install the correct type of light switch with a field resistor and "FIELD" terminal on it!

Current style of AF687R light switch with generator field resistor.

Thank you for the additional information. Off the "Load" terminal it comes. This forum is a Blessing. Best regards, Gene

John T · Dec 2, 2021

Off the Load terminal it comes

Wise choice !!!!!!!!!!!

Best wishes now take care

John T

Eugene Johnson · Dec 2, 2021

Thanks John. Am shopping for an overnite switch. Best regards
, Gene

Jim.ME · Dec 2, 2021

wore out and John T have the correct answer for your problem. A bit of background is that your generator, having just a two terminal cutout relay connected to the armature terminal, indicates it is an original 3 brush type generator. The cutout should close when it senses generator output above battery voltage and open at shutdown or when the generator output drops to prevent voltage discharge through the generator. The third brush provides the regulation for normal charging. The three-position light switch provides an "override", by giving a ground to the field, to allow temporary increased charging for things like a low battery or lighting use. Your Operator's manual explains how and when to use the switch and adjusting the third brush if needed. If you don't have one you can download a free copy at https://techpubs.deere.com/ . Click on Equipment Publications and do a Model Search for H on that page.

John T · Dec 2, 2021

The correct manual Low/High charge control switch for those two wire cutout relay (NON VR) systems will have a terminal that connects to the
Gennys FLD post which will have near zero ohms resistance to case/frame when set to HIGH charge but a few ohms resistance to case/frame when
on LOW charge. Thats the correct place to wire the gennys FLD post. Of course the switch itself needs a good clean case/frame Ground so
theres no to low resistance to the grounded battery post............ You're on top of this yayyyyyyyyyyyyyyy

John T
Brillmans Low High Light Switch

dan_41jdh · Dec 2, 2021

Here's a wiring diagram specifically for the "H".

Eugene Johnson · Dec 2, 2021

(quoted from post at 15:24:14 12/02/21) The correct manual Low/High charge control switch for those two wire cutout relay (NON VR) systems will have a terminal that connects to the
Gennys FLD post which will have near zero ohms resistance to case/frame when set to HIGH charge but a few ohms resistance to case/frame when
on LOW charge. Thats the correct place to wire the gennys FLD post. Of course the switch itself needs a good clean case/frame Ground so
theres no to low resistance to the grounded battery post............ You're on top of this yayyyyyyyyyyyyyyy

John T

Gentlemen: Thank you for all the information. The response was wonderful.
The field is disconnected. I have a work-around for Sat Night parade: as it is a short route I will be able to get by with battery only- no gen.
I will order the proper switch. FYI: I did obtain the harness and magneto from Brillmans and was impressed with the quality of the harness; the magneto was exactly what wasneeded to get the JD H running. Gene

Model H Electrical Puzzle

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