6 Volt Battery Polarity Reversed!

6 Volt Battery Polarity is reversed?

Gene DeMaio I have a 1950 8N. It was my sons and he brought it to my place to use as he no longer had use for it. It started and ran good for 3 years that I’ve had it although I have only used it spareingly.I noticed that the ammeter ran to the discharge side when running but figured it was wired backwards as the battery always started the tractor.I looked to switch the wires on it but it has only one wire running through it with the insulation still on it. I suppose this is some sort of induction type meter? The wireing is all butchered up and not at all original. There is an ignition switch and starter button on floor but they don’t work. To start up I have a toggle switch in a wire on side of motor and the solenoid has a button on the rear of it that you press to start. It worked okay but it is just a jury rig in my opinion and is dangerous because there is no ignition transmission interlock and it will start in gear while standing in front of rear tire while pressing start button.I am very careful that it is in neutral and I also depress the clutch while standing on the ground.
This summer I did not use tractor at all. When I tried to start it this fall the battery was low but it did turn it over, however it would not start. I wanted to get it ready for possible snow removal this winter with my rear blade. When I finally ran the battery low after putting fresh gas in tank and trying some starting fluid it wouldnot fire at all. It had been running fine when I parked it last. I put my 2 amp 6 volt charger on it and left it on for several days. This is still a 6 volt positive ground setup. When I went back a couple of days later the battery would not hardly turn at all. I had the red cable of my charger attached to the Plus pole of battery, that goes to the frame with a black cable. The black cable from my charger was on the minus sign on battery that has a red cable going to starter solenoid and into half assed harness. I took the battery into my pole barn and tested it but to get a reading I had to put red cable of my meter on minus post and black on plus. This seems like it is charged backwards? Is that even possible? Has it been this way all along? If I put meter red wire on plus post and black wire on minus post the meter will pin to the left side and off the chart. I will buy a new battery after the holiday but how should I hook it up? This has me baffeled. The points looked sort of ratty so I put new points and condenser in the side mount distributer. The cap looks almost new.I seem to recall something about polarising a generator before using it, is it possible that this thing has been running backwards ? I admit that I am not much of a mechanic and I have thought about bringing it into A shop to have it properly wired but I have to have it running just to get it up on the trailer. I know that there are a couple of electrical experts here from reading this forun from time to time and I would appreciate any input that you could offer.
Bob G. Hi! This osunds like a real interesting problem. I have never heard of a lead-acid a battery reversing its poliarity. A ni-cad will by overdischarging them. Like you say the 8n is positive ground. the generator needs to be po;arised by jumping between the BAT. and GEN. terminals on the regulator. That only applies if you have the generator that should be on your 8n.

I would hook up new battery with the positve post going to ground.

I would get the FO-4 IT shop manual if you plan on keeping the tractor. It has the wiring diagrams needed for the N- series tractors. the orginial starter switches are avaiable so you can get the interlock working. A good feature. I could scan the wiring diagram and send it to you in a personal message if you would like. Let me know

Have Fun!

Glenn Loud Well the first thing you should check is that the leads to your VOM (voltmeter) are plugged in correctly. red to + etc..
You can test it on a small flashlight battery to check.
Lead acid batterys generally will not reverse.(some Other types of cells can)
The wiring harnesses for the N series are Inexpensive, I would just spring for a new harness.
and go from there. I am sure the guys on the board will be helpful. I am redoing the wiring on an naa myself.
Gene DeMaio I used a large battery analyzer that has the leads permanently attached and no way to plug the leads wrong as in a small multi meter.
The battery is for sure in a state of reversed polarity. My main question in my mind is: Did this happen when I attempted to charge the battery on the tractor? In other words, Did I hook up charger wrong and cause this to happen? OR Was the battery always in this polarity all the while that it was starting and running the tractor? I really don’t think that I had it hooked up wrong as the charger will blow a circuit breaker as well as show a large spark when attaching the second lead. None of that happened and I had it hooked up as explained in my original post. If in fact it was running in that way all along then I want to correct it before I ruin a new battery by putting it in with all other things being the same. In regards to polarising the battery by putting a jumper between Batt and Gen; Does that mean that a generater can pump out direct current in reverse polarity, and if this is so then is or was it possible for a previous owner to have run it like that causing the battery to be reversed and my son and then I were un -aware of it because it started and ran okay??? Remember I mentioned that the ammeter ALWAYS did read to the negative side even though it kept the battery up.
glenn loud Well it is possible that the battery came that way from the factory, (maybe the posts are mislabeled. ?)
I would go through the wiring and confirm it is to factory specs, and then polarize the gen and see if you are ok with a new battery.

I don’t see how you could have done it with your charger. I will do some reading and see what I can find out for ya. (many year electronic tech, and just curious now!)

glenn loud Learn something new every day! Yes you can reverse charge a lead acid battery. I did some google search on lead acid battery reversed polarity, and found quite a few explanations.

Yes if the battery is discharged and then charged with the opposite polarity it will “swap” polarity.

and it is possible that the generator was the cause.

That is one reason why you have to polarize fields on the gens from my understanding. I would think it would burn out or damage the regulator but hey
I was wrong on the battery!

Hope this helps some. (you need a battery at the least, and make sure to polarize the generator.

Bob G. I too have learned something here. Never knew that you could reverse charge a lead acid battery.
I would completely replace all the wiring and install all correct parts and start over. You polarize with all connections made BEFORE you start the tractor. Takes just a real short touch of the jumper wire. Years ago my 1949 ford car, when I replaced the generator, would not charge until I polarized it.
Good Luck
Merry Christmas!


  1. pat baker:

    Hi, I have 6, 6 volt deepcycle golf cart batteries for 36 volt system. Someone hooked charger cable onto 5 of them. The 6th battery reversed itself. Now that I discovered this I’m charging all 6 together and reversed #6 battery which had a full charge but backwards.It runs fine but should I attempt to reverse it back to normal by discharging and recharging in the right direction? Pat

  2. Tim:

    Yes if you discharge the battery then hook the cables up red to ground it is posible to reverse the polarity of the battery to correct it discharge hook up correctly then recharge (discharge to avoid spark and damage to charger

  3. silas:

    hi, need some help. i have a ferguson 1951 with a new 6volt+ ground battery.runs great im going to leave it at camp . i have a 6volt solar charger i was going to leave on the tractor to keep it charged but im not sure where to put the leads on the battery

  4. Hunter:

    Pos to pos, neg to neg always!!!

    You can buy 12 vt reverse polarity chargers, not sure if they’re available for 6 vt bats though.
    If yer gonna use it for bat maintenance use a “trickle” type charger.

  5. bud braun:

    The party was right about reversing the polarity ;touch the battery hot lead to the fields lead on the regulator .This reverses the polarity in the gen. not the battery .. Make sure the battery has been hooked uo tp pos ground….

  6. Rick M:

    My father in law has a 1950 dodge 1 1/2 tom with a 6 volt system in it. we need to reverse the polarity ( we have replaced the regulator and battery), but it discharges and we were told that we have to reverse the polarity but we are not sure what steps you have to do to do that can you please help with step by step instructions…. would be greatly appreciated…. thanks Rick

  7. Gene Nicholson:

    I have seen reverse polarity several times. The residual magnatism in a generator can even be neutral. If the Batery is dead enough, re polarizing the gen to charge correctly did no harm to the regulator or battery. (There could be exceptions)
    I was shop manager for a Ford tractor and equip. for 18 years. Your 8N brings back a lot of good memories. Electrical was my “corner” . Once when batterys had lead bars out on top between cells, I bought one with one cell installed backward.

  8. Robert Walker:

    Oh yes your battery is charged backwards. Easy to fix. Hook up to a draw,example a head light. Leave it until there is no sign of life left in battery. Over night good. Then recharge red to pos. black to negative. Hook up don’t start. Polarize generator . Start up. wow problem solved.

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