Six volt positive ground question

[JRS]

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]

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]

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]

</font><font color="blue" class="small">( The generator is physically positively grounded because it is bolted to the tractor )</font>

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]

</font><font color="blue" class="small">( Most of the antique tractor generators are polarity swappable by repolarizing... One of the few advantages of a generator over an alternator....
)</font>

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]

</font><font color="blue" class="small">( 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 )</font>
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.

</font><font color="blue" class="small">( What happens if someone puts the battery back into the tractor the way the book shows? )</font>

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..

</font><font color="blue" class="small">( What if they are jump-starting the tractor and don't notice that polarities have been reversed )</font>

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...

</font><font color="blue" class="small">( How is your Jubilee set up? )</font>
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]

</font><font color="blue" class="small">( Would be no different than that 1 wire 12v neg grnd conversion you mentioned in your message. )</font>

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]

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]

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]

</font><font color="blue" class="small">( 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. )</font>

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.

</font><font color="blue" class="small">( 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.
)</font>

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 ).


</font><font color="blue" class="small">( I think we both agree a lot more than we disagree )</font>

I think you are correct.


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

</font><font color="blue" class="small">( The alternator looks different, there's no visible voltage regulator )</font>
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