Ammeter wired backwards

Sun Oct 27, 2013 10:33 pm

When I turn on headlights before starting tractor, ammeter shows charge rather than discharge. Ammeter shows discharge when tractor is running. I pulled the hood off this weekend and it looks like if the ammeter is wired backwards it has been that way for a LONG time. The regulator to generator wiring is correct and the wire from the harness does go to the starter motor terminal. I would say that the generator being polarized backwards could be an issue, but the headlights casusing charge rather than discharge before start tractor proves ammeter is simply wired backwards. Thoughts?

Re: Ammeter wired backwards

Mon Oct 28, 2013 6:03 am

Certainly sounds like it is wired backwards. This should provide some assistance. I don't know that having it wired backwards will affect anything but which direction the gage goes, I'm sure others know.
cubwiringlate (Small).jpg
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Re: Ammeter wired backwards

Mon Oct 28, 2013 6:33 am

Need more information. Is your system 6 volts or 12? What is the year of your tractor ( the statistical chances are that it is 1960 or earlier)? Is the charging unit a generator or an alternator? Which battery post is grounded, positive or negative?
This information will provide clues as to how this situation occurred.
If all that is too much to ask, the cure probably is to swap all the wires from one side to the other on the ammeter.

Re: Ammeter wired backwards

Mon Oct 28, 2013 6:48 am

Just swap the wires on the ammeter.

When converting from a 6 volt to a 12 volt system this will happen if you do not swap the wires on the gauge. Not knowing if this is the case....I would swap the wires. It is simply "flowing" thru the gauge.

I think that would solve your issue.

Re: Ammeter wired backwards

Mon Oct 28, 2013 7:39 am

One of the reasons for the questions is that the described backward reading ammeter could be caused if the 6 volt battery is installed with the negative grounded, then the generator is polarized. Moving the wires on the ammeter in that case deals with the symptoms only.
If a generator regulator is built for a specific polarity, and some are, it will work on the opposite polarity but the point life is significantly reduced.

Re: Ammeter wired backwards

Mon Oct 28, 2013 8:18 am

It's a 57 with original 6 volt positive ground and generator. It was this way when I bought it and suspect it has been for a long time. Perhaps originally

Re: Ammeter wired backwards

Mon Oct 28, 2013 8:22 am

Original wiring also. Could the battery be installed backwards and still work?

Re: Ammeter wired backwards

Mon Oct 28, 2013 8:32 am

If your tractor has no issues with keeping the battery charged, I would say just swap the wires as has been mentioned...If it does not keep the battery charged you need to investigate further....Dave

Re: Ammeter wired backwards

Mon Oct 28, 2013 8:53 am

I probably answered my own question. These 6 volt batteries are probably symmetric. The starter doesn't care, nor core, regulator, or lights. That's how you do a 12 volt neg conversion with alternator conversion.

Re: Ammeter wired backwards

Mon Oct 28, 2013 9:53 am

I would also buy or borrow a voltmeter and check the polarity of the battery. They can be charged backwards resulting in the + term actually being negative etc. This would also give the same results. I learned that in 69 or 70 trying to figure out why the radio wouldn't work in a late 50s or early 60s Chevy (don't remember exact year). Kid had taken battery out to take to the field and jump start a Farmall M that was dead. When he reinstalled it, somehow along the line the generator became polarized the wrong way, and he made a long trip in it . No ammeter, only an idiot light, and he never knew anything was wrong, it had enough running time to discharge the battery and recharge it in reverse polarity. The only noticeable problem was the radio would not work. He brought the radio to the shop twice and I could find nothing wrong with it until he finally brought the vehicle in, and as son as I hoked a volt meter to it I saw why the radio would not work. I told him to leave the lights on that night and run the battery down then to recharge the battery with a charger, and showed him how to polarize the generator afterward. All was well afterward, but i do not think the battery lasted as long as normal afterward.

Re: Ammeter wired backwards

Mon Oct 28, 2013 9:12 pm

I'm anxious to check the polarity of the battery, but alas it is out at the farm and won't be able until this weekend. I assumed that the previous owner had hooked up the new battery correctly. Obviously not a good assumption. Thanks for everyone's suggestions.

Re: Ammeter wired backwards

Tue Oct 29, 2013 11:53 am

Astrowing wrote: I assumed that the previous owner had hooked up the new battery correctly. Obviously not a good assumption.


Unfortunately not, as not everyone has experienced a vehicle wired positive earth. I only know about it because my first car was older than I was. :D

Re: Ammeter wired backwards

Sat Nov 09, 2013 10:38 pm

The battery is wired correctly, but is reverse polarized. I was surprised when I put my voltmeter on it. Ive never seen this before myself. Tried to run the battery down and then recharge with correct polarity but didnt work. ive got a new battery installed and will repolarize the generator before restarting.

Re: Ammeter wired backwards

Sun Nov 10, 2013 7:37 am

That will be a good approach and everything should work normally after you do that. When correcting the polarity of the old battery, it needs to be drained absolutely dead. Connect a load across it, such as a light bulb, and drain till you see no sign of life, then leave it connected for another day. Once it,s totally dead you should be able to charge it the proper way.

Re: Ammeter wired backwards

Sun Nov 10, 2013 8:08 am

Gary Dotson wrote:That will be a good approach and everything should work normally after you do that. When correcting the polarity of the old battery, it needs to be drained absolutely dead. Connect a load across it, such as a light bulb, and drain till you see no sign of life, then leave it connected for another day. Once it,s totally dead you should be able to charge it the proper way.
There's one for the old memory bank...