Six volt positive ground question

JRS · Aug 31, 2004

I just bought a Ford Jubilee with the original 6 volt system. The shop manual says it has a positive ground but the 6 volt battery that's in it has been installed as a negative ground. What are the issues with the battery installed as a negative ground vrs the recommended positive ground. Easy to change but has anything been damaged because of this. I don't have any idea how long it has been this way. The tractor runs but the carb needs to be rebuilt. Runs rich with and will not lean out with the adjustment screw.
Thanks in advance. John

jinman · Sep 1, 2004

JRS, if your Jubilee has the OEM generator and voltage regulator, there is no way a negative ground should work. The generator is physically positively grounded because it is bolted to the tractor. I don't know how it would work without blowing up the battery. I wouldn't run with that setup.

On the other hand, if the tractor is changed to a 12-volt system with a one-wire GM style alternator, everything works fine on negative ground. Even your starter motor turns the same direction no matter what polarity.

I just think there is something you haven't discovered if the battery is in backwards. What does the ammeter say when the tractor is running? Does it work?

Soundguy · Sep 1, 2004

I have a NAA which is the 1954 model of the 53' Jubilee.

I've also got a few other fords..and some other antiques that are 6v systems.

Yep.. it was oem 6v pos grnd. Nice thing about these generators is they can be poplarized to run negative ground.

Is it charging right now? If so.. you know the regulator, cutout, and the genny are working.

The big issue with positive ground is based on the 'eddison effect' and has to do with the spark plugs, and ground planes, and the spark itself. Fairly complicated to explain.. but if you want to do some research on your own.. lookup 'edison effect'.

The other issue is the ignition coil. That unit used a side mounted roundcan ignition coil ( readilly available.. at places like TSC.. and online...etc. ) If the previous owner swapped the ground, and repolarized the genny/regulator that is good. However most people forget to swap the ignition coil polarity around. Ignition coils can loose up to 40% of their spark potential when run with the wrong polarity.

The oem coil were marked with 'batt' and 'grnd' .. new ones are marked with '+' & '-' . If you have a new one.. simply match the side of the coil to the correct connection based on polarity. The distribuitor is considered ground.. as the points open and close, grounding the circuit. Thus on the old setup, grnd went to the distribuitor, assuming that was positive ground. if you leave it negative ground.. you need to swap it over so it shows batt to the distribuitor.. However.. if it still has the old coil.. replace it. The newer oil filled coils provide much better high voltage. The new one will have the +/- as well.

The genny on that tractor is a 2 brush 3-wire B-circuit genny, if it is original. You repolarize by swapping the battery connections around back to positive ground, and then using a jumper wire, jumper the batt and field wires together momentarilly... might spark.. that's ok. This polarizes the cutout relay in the regulator, and the field poles in the genny.
( b-circuit gennies provided field power via the vr field terminal to energize the internally grounded genny field coils.. the jumpering gives them momentarilly max field power ).

( On the older N's like the 8n that had a different 2 brush 3 wire genny.. they were a-circuit.. and you polarized by jumpering batt and armatue. .. The a-circuit vr field tab provided field ground to the internall hot field coils in the genny.)

Either repolarize that system.. or at least make sure the ignition coil is hooked up correctly for the non-oem polarity. I'll bet you'll get hotter sparkies that way.. plus if you changed the coil.. that may help.. unless it is already a newer style coil.

Let me know if you have any other questions.

Soundguy

Soundguy · Sep 1, 2004

( The generator is physically positively grounded because it is bolted to the tractor )

Keep in mind that the tractor frames ground potential is determined by what post of the battery is tied to ground. A tractor is only positive ground frame if the positive battery post is tied to the frame.

Most of the antique tractor generators are polarity swappable by repolarizing... One of the few advantages of a generator over an alternator....

Soundguy

jinman · Sep 1, 2004

( Most of the antique tractor generators are polarity swappable by repolarizing... One of the few advantages of a generator over an alternator....
)

Yep! You could surely do that, Soundguy. Of course, the shop manual would be wrong and in my opinion that creates an unsafe situation because you have a non-standard situation that could cause problems. What happens if someone puts the battery back into the tractor the way the book shows? What if they are jump-starting the tractor and don't notice that polarities have been reversed? If it were my tractor and I wanted to stay with 6 volts, I'd make sure the generator was polarized according to spec. I think you would too. How is your Jubilee set up? /forums/images/graemlins/confused.gif

Soundguy · Sep 1, 2004

( the shop manual would be wrong and in my opinion that creates an unsafe situation because you have a non-standard situation that could cause problems )
Would be no different than that 1 wire 12v neg grnd conversion you mentioned in your message. Both would be examples of a deviation from the factory norm.

( What happens if someone puts the battery back into the tractor the way the book shows? )

Then I'd say that the person installing the battery backwards fromthe current system would learn via the school of hard knocks, and make an expensive mistake. Any time I disassemble something with wires on it.. I ALWAYS make a diagram og it.. or tape/tab the wires so I know how to hook it back up. Doesn't have to be an intricate drawing.. even something scratched onto an empty cardboard box, or empty horse feed bag. Battery polarity is a big issue that should always be paid attention to when removing or replacing a battery.. and that is what should be relied upon.. not the book.. However that said.. if you do go by the book, ( the shop manual that is.. ) it states that every time the battery is removed, or the vr, or the genny, that the system should be repolarized. Doing that would prevent any catastrophic high current meltdowns, leaving only a small issue of mismatched ignition coil polarity.. which doesn't damage anything.
Another issue is sloppy mechanics. If nothing else.. the battery post ends should not fit correctly if you tried to install them backwards.. as long as the previous mechanic used the correct ends..

( What if they are jump-starting the tractor and don't notice that polarities have been reversed )

Two problems with that argument. 1st, if you are dumb enough to reverse polarity connect two batteries vai jumper cables.. you deserve whatever happens... I see that as evoloution in progress. Batteries are clearly marked with a big molded in "+" and "-" sign on the batteries.. and thats how you hook them up.. positive to positive, ngative to negative.. irregardless of each vehicles ground polarity.. just make sure the vehicles are not touching. Adding to that.. safe jumping usually doesn't involve making the connections on the battery itself .. and al you have to do is follow the big cable from the battery terminal to see what it connects to to see where your connection point is. 2nd If you are jumping a 6v tractor ( positive OR negative grounded ) from a 12v source, you don't ever jumper battery to battery.. but instead jumper battery to starter.. Otherwise you get lots of current flowing.. and more volts per cell than that 6v can handle.. possibly making it explode... again.. evoloution in progress.

Proper way to jump a 6v tractor is to put it in neutral, hook up your booster cables to the 'donor' battery, attatch one cable to the starter top post, and then use the other cable for the ground connection at any convienient point. This amkes the starter spin over immediatly, so if you want it to start.. the ignition will need to be on. On starters with a powered field, and no permanent magnets, they usually only spin one direction regardless of polarity, however I usually like to try to hook up my boosters to match the 'dead' vehicles polarity in case of things like stuck solenoid contacts.. etc. Also gets you areound the problem of deciding whether the starter has a powered field or a permanent magnetc style... Just gotta be carefull and make sure it isn't in gear...

( How is your Jubilee set up? )
12v neg grnd.

My 8n is 6v pos grnd..
my 2n is 12v neg grnd
my jd-B is 6v pos grnd
my 66 ih cub is 12v neg grnd

Soundguy

Soundguy

jinman · Sep 1, 2004

( Would be no different than that 1 wire 12v neg grnd conversion you mentioned in your message. )

You have a point. I wouldn't say "no different" but I agree the 12v negative ground is not standard. It's also not likely that anyone having that system would not know it. The alternator looks different, there's no visible voltage regulator, and of course the battery looks different. If I walked up to a Jubilee with a generator I'd automatically assume it was 6 volts and if it had an alternator I'd assume 12 volts. Having said that, I agree that it's not standard. You and I both know the benefits, so I don't need to go into that.

I guess the rest of your post is what I have the most disagreement with. I agree there are many foolish things that could be done, but I don't believe in "stacking the deck" or allowing a "booby-trap" to persist. Just because a person is makes a mistake doesn't mean they "...deserve whatever happens." I don't really believe you think that way either.

Actually, Soundguy, you gave an excellent explanation of how the Jubilee could be reverse wired. I didn't know it was that simple. Your expertise is very high and I surely didn't mean to offend you. I think we both agree a lot more than we disagree. /forums/images/graemlins/smile.gif

bland · Sep 1, 2004

Hey soundguy, straighten me out here. As I read this thread, I got to wondering about the 8n I just bought a month ago. I knew it had a new battery and the more I thought about it, I thought it had not been charging right. Went out and checked and sure enough, new bat hooked up neg ground. I changed it around and started it up - the ammeter acted funny for a little bit then jumped several times then settled down and showed full charge which dropped down as I ran it a while and appeared to act like it should. Before this it hardly showed any charge when running more likely even being in - range. Now the question - my coil has bat and dist markings (not bat and grnd or + & -) dist pole is to dist as hooked up now. The gen has two poles on top - one marked grnd the other not marked and one pole on back. Wondering if I should polarize the system even though it seems to be working fine now. If I need to polarize it, which poles do I short out on the gen? It is dark now, but will look more at it tomorrow if I have time. Also, were you saying earlier that you get a hotter spark with neg ground vs positive ground? If so, maybe I should change it back and change coil wires and repolarize. I am a electrical control tech by trade so I can trace out the whole wiring if I have to, but if you can help I can save having to do that I hope. Thanks.

JRS · Sep 1, 2004

The Jubilee did not come with an amp gauge so I am in the process of buying one and hooking it up. The coil shows negative and positive signs with the negative going to the distributor. So your saying if it runs I should change the leads on the coil as the generator is already polarized?
Thanks, John

Soundguy · Sep 2, 2004

( agree there are many foolish things that could be done, but I don't believe in "stacking the deck" or allowing a "booby-trap" to persist. )

A modification to a piece of equipment is not a stacked deck.. or a booby trap. If I'm buying a piece of equipment in the 50-60 year old range.. i -expect- it to be in a non factory condition, rather than expecting it to be oem. A very quick visual exam is all that is necescary to identify battery polarity.

( Just because a person is makes a mistake doesn't mean they "...deserve whatever happens." I don't really believe you think that way either.
)

Yes and no. No.. I don't specifically wish any harm to anyone.. including people I dislike. Nor would I intentially set up a 'trap' for people.. however in this day and age.. common sense is more and more uncommon, and consumer safety laws are driving me crazy. These laws are the reasons we have to have a sign that says " Caution.. coffee is HOT" or a label that says " May contain peanuts.. on the sid eof my peanut butter'. In general.. most of these laws are the results of lawsuits. Reminds me of the label my push lawn mower has.. it shows a warning about putting the hands under the deck... I immediatly get a vision of a guy with no fingers... I'm no rocket scientist.. but if the grass gets cut under a mower.. then.. um.. -everything- gets cut under a mower... that's not a difficult conclusion to arrive at. And no.. I don't specifically wish harm to the guy with the mower.. however the person misisng a hand is an idiot in my book, and he was heading down that 'natural selection' path full speed ahead. No.. they may not deserve what happens.. but they are responsible for it... it isn't an accident.. but an error. ( on their part ).

( I think we both agree a lot more than we disagree )

I think you are correct.

I still don't think changing the charging system on a machine makes it a booby trap though.

( The alternator looks different, there's no visible voltage regulator )
Actually. the alternator on my NAA is so old.. it DOES have a square external regulator.... it's not one of those new gm internal jobs...

Soundguy

Soundguy · Sep 2, 2004

( The Jubilee did not come with an amp gauge so I am in the process of buying one and hooking it up. The coil shows negative and positive signs with the negative going to the distributor. So your saying if it runs I should change the leads on the coil as the generator is already polarized?
)

Lets see. If your coil shows a '-' and a '+'.. then it is a newer coil. Match the polarities. If you have a negative ground.. '-' goes to the points.. if you have a positive ground, '+' goes to the points.

Soundguy

Soundguy · Sep 2, 2004

( If I walked up to a Jubilee with a generator I'd automatically assume it was 6 volts and if it had an alternator I'd assume 12 volts )

I wouldn't. The NAA are very similar in appearance to the hundred series.. same sheet metal. In fact they look virtually identical, except that NAA rear hubs have an axle nut, and hundred series hubs had a small dished in hub. At 30' away.. they are 'the same' looking. Hundred series and especailly the diesels had 12v gennies and 12v conversions/upgrades for the first 6xx series that were still 6v.

Hard to identify a genny without measuring the field, etc. even looking att the battery can lead you wrong. When i bought my 1950 JD-B it had a 12v negative ground battery int he box, and the generator chage wire was wire nutted off inthe compartment. It came from the factor 6v pos grd.. I checked the voltage at the armature on the genny while full fielding it, and found that it was till setup for 6v pos grnd.. and still worked. I put the correct 6v battery in their, pos grnd, and hooke dthe genny up. When full fielded, it will charge at 7 amps.. just like the manual said.

Alternators don't automatically make me think 12v or neg grnd either. I've seen too many 6v alternators.. especailly on the older tractors. Same with the grnd. positive grnd alternators are more rare.. but deffinately out there.. same with isolated alternators. Some of our heavy equipment use iso alternators.. they have both a negative and positive output lug, and the case of the alternator is isolated fromt he electronics..so ground polarity for the frame of the vehicle is up to you.

I also allow for the fact that a lead acid battery can be charged backwards.. I've seen it many times.

When it comes to electronics.. I simply don't assume anything that I havn't put my meter on untill I see the polarity, and the voltage reading on the armature of a genny or the output stud on the alternator.

Soundguy

Soundguy · Sep 2, 2004

( it up - the ammeter acted funny for a little bit then jumped several times then settled down and showed full charge which dropped down as I ran it a while and appeared to act like it should. Before this it hardly showed any charge when running more likely even being in - range. )

That negative on the meter was probably the ignition draw on the battery. Most likely the genny was polarized for positive ground, and with the battery hooked up negative ground, the genny wasn't charging. The reason why the whole thing didn't smoke was the cutout relay in the VR. The cutout relay is a bit of wiring magic. I won't go into the whole specifics.. but a vr has current and voltage relays.. anyway.. the cutout doesn't 'close' and connect the armature and battery connections untill the voltage on the armature exceeds the voltage at the battery. When you hooked the battery up correctly, it started charging, like it was polarized for. The bouncy needle readings are common when the cutout closes and the field current adjusts back and forth for a few seconds ( it is going from no load to full load ).

( Now the question - my coil has bat and dist markings (not bat and grnd or + & -) dist pole is to dist as hooked up now. )

That means you have an older oem style coil. In that case.. distrib meant grnd.. and oem it was positive grnd. If you are now positive grnd.. dist goes to ground (+ ). etc. ( If i were you I'd get a new oil filled coil from tsc.. the 6v ones are less than 20 bucks and will outperform the oem 6v coil big time... )

( The gen has two poles on top - one marked grnd the other not marked and one pole on back )

Grnd pole on the casing is ground to the genny case.. and is also the ground reference wire for the genny.. it is good to have a ground reference for your genny running to the vr to make sure there are no differences in ground. For instance.. painted frame may make a minute difference in ground reference at the genny / vr.. that results in a ground loop, and incorrect field control. The other pole on the case is insulated with a fiber or phenolic washer.. it is field. If this is the 2 brush oem genny, the field is internally hot, and needs a ground reference from the genny field tab so that variable field current can flow via the vibrating field contacts in the vr.

The large stud on the back of the genny is the armature.. it is the output stud.

( Wondering if I should polarize the system even though it seems to be working fine now. If I need to polarize it, which poles do I short out on the gen )

If it is working now.. don't fix it. Although, repolarizing a genny multiple times will not hurt it. If you ever did need to repolarize it.. on the a circuit gennies you short the armature to the battery 'hot' So on a positive ground system, you are jumpering the armature over to the battery negative post which is also hooked up to the side of the starter solenoid. This polarizes the genny field, for charge polarity, and also polarizes the regulator cutout relay for correct operation.

( Also, were you saying earlier that you get a hotter spark with neg ground vs positive ground? If so, maybe I should change it back and change coil wires and repolarize. )

Yes / no. Due to the edison effect.. the positive ground system works well.. ( has to do with the spark plugs, gap, and discharge.. electron theory.. etc.. ) That said.. if you have the later 8n with the side mount coil, you can run it either negative or positive ground as long as you have the igniton coil matched and wired correctly, with no change in high voltage.. though positive ground may make the spark plugs last longer. If you are using a front mount distribuitor and square coil.. it is hardwired, and should really only be run positive ground when on a 6v system, because otherwise you do sacrifice some high voltage.

If you have it back pos grnd.. and have the coil hookd up correct.. leave it.. unless you want to change it.. it is already setup for optimum efficiency ( unless you want to upgrade that coil.. ).

( but if you can help I can save having to do that I hope )

I agree.. if it's working.. don't fix it.

The only differences you may find with what i wrote, is if your genny is not the oem 2 brush a circuit setup. There was a lso a 3rd adjustable brush genny that had the field contacts on the housing.. but was only used on the very early 8n.. if you have an 8n with a side mount distribuitor and coil.. it should have come with the 2 brush genny. In rare cases a genny shop may have accidentally rebuilt the genny as b-circuit like a hundred series genny.. if so. it uses a different vr, and polarizes differently. But again.. you's is working.. so no need to worry about that...

Soundguy

Soundguy · Sep 2, 2004

JRS. just a quick reminder as this thread strayed a bit from your question.

Just remember that your NAA genny is a 2 brush B-circuit genny as from the factory, and polarizes differently than the 8n 2 brush A-circuit genny that I've also been talking about.. just don't want anyone to be confused here.

Soundguy

slowrev · Sep 2, 2004

Several tractors and Cars/trucks came out with 12V Generators. My friend has a 5000 ford with 12V generator (Lucas) as standard. I actually like generators better if they can handle the load. Battery lasts longer as it does not charge as fast.

Soundguy · Sep 2, 2004

I personally like generators better myself as well... no diodes to worry about.. just lots of copper and brushes... fairly forgiving for minor problems, and generally start dieing slowly and just charging less rather than an alternator thet generally dies spectacularly.

Also.. I've seen a system with a dead battery and a generator be push started and run.. they disconnected the battery, and ran it down a hill... the genny spun enough for ignition current and it started.. they popped the battery in it and went..

Soundguy

Egon · Sep 2, 2004

[Lucas]

THE KING OF DARKNESS

Egon /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

Soundguy · Sep 2, 2004

Yep.. lucas.. prince of darkness.. and flaming death..

Soundguy

garretreed240 · Feb 27, 2014

I have a 1960 Farmall 240 and has a 6-volt. I was wondering if that model has the positive ground? My battery wont hold a big enough charge to turn the motor over. The battery isn't even a year old so it cant be that. I bought the tractor 3 years ago and im wondering if the previous owner swapped the cables to a negative ground not knowing what he was doing. Can anyone give me a little advice on it?

DJ54 · Feb 27, 2014

Yes, it is positive ground. Does the amp gauge show that it's charging..?? If not, I'd guess either the generator, or voltage regulator, or both are not working. If it is showing charge, it may be your battery cables need cleaned (especially the ground), a bit loose, or are not heavy enough.

If they've been replaced with automotive type like 4ga., they aren't heavy enough. Some NAPA's, Ag. Dealers, or Construction Eq. dealers can make you a custom set, and nothing less that 1/0 cable. It will make it start like a new one if everything is up to snuff.

If you're jumping to start, or charging to full charge, then starting, it will run a good while on a charged battery, and the ignition system is drawing the battery down if the charging system is not replenishing the battery.