12 v positive or negative ground

equeen

Member
Manual on a non-Ford tractor calls for positive ground. Battery in tractor is 12 volt negative grounded.

What problems are created, if any? Should this affect generator, VR, solenoid, etc?

Should it even operate unless this tractor was designed and maintained as a negative ground unit.
 
gennies will operate pos or neg ground.

mechanical vregs will as well.

MOST alts are setup for NEGATIVE groud.

what do YOU have?


( yes.. pos or neg ground.. the engine do't really care.. runs the same.. )
 
Brother has a 64 Massey Ferguson 12v with generator. Gen shop installed new brushes and gen checks out fine. Battery is not charging.

With all wires connected and engine running, get 2.68v when jump ARM and FLD terminals. No voltage when jump ARM and BAT terminals. New VR on order.

But, wondering IF the battery was - and remains - installed incorrectly, will it cause problems. Some reports that MF 35 had both neg and pos ground batteries, but the manual calls for positive ground.

Thanks for your ideas.
 
equeen there are some vehicles (I say vehicle because some autos (Chrysler) are positive ground) that use a positive ground. Whom ever is doing your generator should be able to tell you if it is a positive or negative ground. If you have a positive ground system in your tractor and you hook it up as a negative ground it will fry your generator. And possibly some other systems, i.e. starter, amp gauge it can even melt wires.
 
really don't matter.. just polarize gen for whatever bat polarity you have, assuming a mechaincal vreg.

now.. is that charge system B circuit? you said you jumped arm to field. that indicated B circuit.
 
really don't matter.. just polarize gen for whatever bat polarity you have, assuming a mechaincal vreg.

now.. is that charge system B circuit? you said you jumped arm to field. that indicated B circuit.

Okay....
1. I'm assuming a mechanical VR. Arm in back, Fld at top side, Bat at middle side, Lights at bottom side. What other type VR is there for these old tractors?

2. Polarize gen for negative ground (currently)? Instruction I have is to temporarily ground the gen FLD to the case or frame; then momentarily flash jump from VR BAT to the VR ARM term. (Should get small spark.)

3. What determines battery polarity?

4. What in the world is a "B" Circuit?

Thanks
 
yuo are all over the place.

your last post said you jumped arm to field... which indicates a B circuit system

NOW you are saying you are jumping bat to arm.. which indicates an A circuit system.

you REALLY should become familiar with your machines functions.

A and B circuit refer to field circuit types int he genny / vreg combo.

As for regulators.. there are mechanical vibrating regs.. and in some cases.. you can get solid state vregs. solid state vregs are generally NOT polarity agile.. the mechanical vregs, even if designated / designed for a polarity type, generally will work with either polarity.
 
Yes, I see that I was all over the place. Back to my notes.

Jumped from ARM to FLD and had voltage.
Jumped from ARM to BAT and had NO voltage.

Exactly opposite of what I was expecting to find.
 
if it's A circuit and you jump arm to field.. you may have cooked your vreg.

you just cant grab wires on tractors and start touching them together without knowing what you are doing.

IF it is A circuit.. you ground the field, and should read max on the armature.

IF it is a B circuit you can jump arm or bat to field and that will make it charge max at armature.

I don't konw which field type your machine is.

apparently you don't either.

I encourage you to find out what type it is so you don't roast a vreg.

if you flip the vreg over look for a bias resistor between ground and field.. if it has that one only.. it is an A circuit regulator.

if it has one from arm to field and perhaps another ( optional ).. it is B circuit.
 
Thanks for all your comments.

Will visit again and inspect VR with brother before new one arrives.

Notes were from some forum year or so ago regarding a 6 volt negative ground system. Is there a problem with these instructions for "Quick Test of Voltage Regulator with engine running and wires to generator connected":

1. Using volt meter momentarily jump the ARM and BAT terminals. Charge should be about 7.8. If not, then replace the regulator.

2. Jump the ARM and FLD terminals. If there is a charge, then replace the regulator.

Still learning and taking notes.
 
they both DO NOT apply to the same type of field circuit.

you can't use generic info, mixed togehter like cookie dough, and then apply it to stuff it does not apply to.

i gave you info in my last post how to determine what circuit type your reg is. if that reg is the specified one for your machine..and you have the oem genny.. then you know what circuit type the machine is.

from there.. you know how to polarize it

( bat to arm, when not running polarizes 'A' circuit.... when running, field to ground provides max charge test )

( bat to field, when not running polaraizes 'B' circuit.. bat to field when running provides max charge test. )


It's simple...

throw that note you have away.. it's only good for roasting vregs.

you can't blindly sift thru a forum for generic electrical info and then HOPE it applies to what you are looking for. do your tractor a favor.. get a service manual for it. it will love you for it. :)
 
You posted some bum info that will confuse.reverse polarity will not fry your generator, ammeter,amp gauge.Starter turns the same way, pos or neg.1/2 the vehicles built in 1940 were positive ground.All 6V tractors Ive worked on were pos ground.Reversing polarity on an alternator will damage it.
 
i'm not riled up.. i'm trying to HELP you.. but you can't mix n match shopping bag style when it comes to some repair advice.

gotta match up like applications...
 
I understand.

I did check some spare VRs for my 8Ns and its easy to see the bias resistor of which you wrote.
"A" circuit.

Checked a cut-out for the cubs and....well.

I'll check the one on the MF 35 next time I'm down at my brothers.

And, no, I'm not following all your advice. I'm not throwing all my notes away. Your advice appears sound and worth retaining.

Me
 
you can throw the one away that tells you 2 different things on that genny without telling you what circuit type they apply to.

cutouts and vregs are setup differently. the bias resistor is a field circuit component.. cutouts don't have that.

that cub is likely A circuit using a tickle ressitor in a lamp switch or similar...
 
equeen, might I suggest you at least do a thorough review of your notes?
The one you posted here says to jumper with a voltmeter.
I can't see what that would get you except a voltage reading.
It also has the same result for both scenarios. Replace the regulator.
If you're just going to replace it either way, why do the tests?

"1. Using volt meter momentarily jump the ARM and BAT terminals. Charge should be about 7.8. If not, then replace the regulator.

2. Jump the ARM and FLD terminals. If there is a charge, then replace the regulator. "
 
Royce,

Objective was not to just go willy-nilly and change out VRs, gens, etc; but rather to test to see what works and what doesn't.

1 & 2 were results of questions relating to a 650 Ford. My understanding was that there is a measurable reading from ARM to BAT IF the VR is good - if not, then replace. Further, there should not be a measurable reading between ARM and FLD is VR is good - thus replace if get a reading.

In fact, those instructions seemed to have been reliable regarding an 8N and a 650. But, will verify or correct notes at the proper time.


But, no one should take my word for anything. I'm the trainee/learner, not the wizard. Pleased that lots of experts respond to posts such as mine - and try to get me on the "straight and narrow".
 
Been watching from sidelines, but have a question for you, equeen, when you say, "jump from ARM to BATT", what does that mean? And when you speak of "see a reading" or "see no reading", are you referring to voltage, amperes, or Ohms?
 
Apologize for my wording/terminology.

I'm actually checking for voltage reading with one probe on the ARM terminal of the VR, the other on the BAT terminal of the VR, etc. Thus, I either see a reading or else see no reading. This is done with the engine running, all wires connected, etc.
 
(quoted from post at 19:43:23 03/23/13) Apologize for my wording/terminology.

I'm actually checking for voltage reading with one probe on the ARM terminal of the VR, the other on the BAT terminal of the VR, etc. Thus, I either see a reading or else see no reading. This is done with the engine running, all wires connected, etc.
was beginning to suspect that. You see, about most of the population will take "jump from A to B", to mean that you shorted A to B with a jumper wire or a screwdriver or pliers or some other conductive object, rather than that you connected a voltmeter between the terminals, A and B. Clear communications is difficult! Sender & receiver may end up in two different worlds. This I'm afraid makes much of what has been said, null & void.
 
Thanks for getting me on the right track with my terminology. Yes, I can see that words do make a difference - and my words can get wacky.
 
I've been following this discussion, and piecing things together it appears that

The tractor in question is a Massey Ferguson 35. Diagram at FENA dot org / resources / wiring diagrams / MF35 shows it is 12 volt, negative ground and regulator shows Type A circuit (field of generator to grounds through regulator.

The notes in question are for a 650 Ford which would be a type B charging circuit.

Looking at the notes:
"1. Using volt meter momentarily jump the ARM and BAT terminals. Charge should be about 7.8. If not, then replace the regulator.

2. Jump the ARM and FLD terminals. If there is a charge, then replace the regulator. "

Let's apply some life experience to note taking and understand that notes are often quickly written and later confusing to read.

With that in mind lets interpret note as probably intended:
1:Using volt meter (CONNECTED ACROSS THE BATTERY) momentarily jump the ARM and BAT terminals. Charge should be about 7.8. If not, then replace the regulator. This bypasses the cutout section of the regulator and would make sense.

Note 2. Jump the ARM and FLD terminals. If there is a charge, then replace the regulator. " applies full field to a TYPE B SYSTEM and tests the regulator side of the regulator box.

If applied to MF35 (Type A) it should be GROUND THE FIELD TERMINAL

Attached diagram shows difference between Type A and Type B.

A generator system, if properly configured can operate either positive or negative ground
a108371.jpg
 
Thanks, rvirgil. Thanks especially for the link to the wiring diagram on the MF 35 - showing NEGATIVE ground. Interesting, indeed.

(Everyone else ignore this paragraph so as not to confuse anyone). Brother has a MF35 manual on a CD for his tractor. He printed out wiring diagram. He and I looked at the diagram. His concern, then later mine, was that his diagram showed POSITIVE ground, while the tractor battery is installed NEGATIVE ground.

(I shall visit with him and learn the source of his CD manual.)

In any event, rvirgil, the link you provided reflects negative ground and his tractor is negative ground. Thus, will assume that electrical system worked fine as configured until the voltage regulator went bad - from whatever cause. Since generator has been rebuilt by "outside shop", is clean-grounded, wiring replaced to VR and new VR on the way - I feel much better about replacing the VR without fear of "destroying" it or the generator.

Very helpful!
 

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