6v, 12v negative or positive ground?

The weather warmed up around here (great southern AZ spring weather) so I started to work on our new to us 40 H (http://ytforums.ytmag.com/viewtopic.php?t=411094&highlight=).

The carb came in the mail to replace the one with the broken ear.
I changed the carb, plugs, checked the mag, made sure it had oil and water in it and decided I really need to get a better idea how bad it is...

I put in the dead 6v battery that came with the tractor so the wires would short on anything.. I installed it as positive ground which is opposite of how it came to us..

I hooked a 12V jump box right to the starter closed the choke, hit the button on the jump box and it fired up in about 2 rotations.. It lives..

I had a volt meter sitting on the battery terminals and saw odd numbers...

With the meter hooked up for a positive ground (red lead on the chassis and black lead on the negative terminal on the battery) I was seeing jumping voltages from -5v to -13v. I let it run about a minute and shut it off since I was getting confused.. The tractor is in good enough shape for me to continue working on it...

My question is... What the easiest way to figure out if its negative or positive ground and if its 12v or 6v? It didn't occur to me until I started to write this that I didn't polarize the generator but I don't know if that would cause something like this.

I haven't started it back up yet since I really need to change out that old oil and filter and replace the hoses and belts and don't want to hurt anything by being impatient and running it with a dead 6v battery in wrong.

Thanks..
~Mark

Mark - A couple ways to determine ground polarity/voltage:

1 - Look at the voltage regulator. It MAY be marked for both voltage and polarity.

2 - With the jump box connected, turn on the lights or ignition and note which way the ammeter deflects. If it goes toward the left (discharge) your ground is correct. However if it deflects right (charge) the jump box is grounded backward.

----

Once the jump box is grounded correctly re-polarize the generator (jumper the BAT and ARM terminals at the regulator together for an instant.) Now start the engine and run at 1/2 throttle.

If the ammeter shows a charge you are all set. However if it still shows discharge either the system is 6 volt, and/or the generator/regulator have other issues.

Good luck!

Mark and Bob M,
If it is 6 volt, hooking the jump box to it might fry the lights. If you want it 6 volts (good option) Get a new (or good) 6v battery before polarizing and tedsting. Don't use the 12v jump box. JimN

Mark and Bob M,
If it is 6 volt, hooking the jump box to it might fry the lights. If you want it 6 volts (good option) Get a new (or good) 6v battery before polarizing and tedsting. Don't use the 12v jump box. JimN

Jim - Good catch on the lights!

You can however still use the jump box but use only the ignition to check ammeter function.

And if it turns out the tractor IS 6 volt, don't run it longer than a few minutes from the jump box. Otherwise you may damage the points and coil.

Mark, great info from my friends and we usually pretty much agree on this stuff, so I will just answer in my owm method n you can go from there..

My question is... What the easiest way to figure out if its negative or positive ground and if its 12v or 6v?

Wellllllll its now whatever ground as you connected it......The next question would be what was it prior???????

Many 6 volt tractors (say an A or B or C or H etc) were originally Pos ground which is a good starting assumption. After you installed the battery, if you turn on an electrical load such as lights or ignition (unless a mag) if the ammeter swings over to - discharge the way you grounded it is "probably" as it was before. HOWEVER if it swings to + charge you have it opposite how it was before ASSUMING the ammeter was correctly wired for the prior ground.

The thing is if you reverse polarity the ammeter leads need swapped or else it will register bass ackwards.

Other grounding hints may be the way the coil is wired if its not a mag and iffffffffff???? it was wired correct to match the polarity. For best performance the coil should match the battery polarity which would be the lil + terminal receiving ignition switched voltage with its other lil - terminal to the distributor and opposite of that for Pos ground...

Hints for what voltage it was prior is what voltage the coil is (unless a mag) and if its a 6 or 12 volt and if perhaps theres an ignition ballast resistor, unless a mag of course


As far as jump starting, if you jump the starter only i.e. on the starter side of a mechanical push start switch or solenoid or right on the starter post itself, you shouldnt hurt anything else as the jump isnt connected to the rest of the tractor electrical system. However if you jump the battery then it does connect to everything and could burn 6 volts lights IFFFFFFF they are on and it could eventually (but would take a while) overheat the coil if youre jumping a 6 volt coil tractor with 12 volts. But a jump only and then having it run on its own correct voltage battery wont overheat the coil if its correctlty sized... Of course the rest of the tractor needs enough in house battery energy to power up the ignition unless its a mag

If its a 6 volt tractor Id install a new batery at Pos ground,,,,,,,,,POLARIZE THE GENNY,,,,,try n start it n see what happens and what the ammeter shows......

QUESTION
It didn't occur to me until I started to write this that I didn't polarize the generator but I don't know if that would cause something like this.

If its started and the gennys polarity is opposite that of the battery,,,,,,,the VR can be damaged and it could cause erratic voltage readings temporarily at least


There ya go

Thats my story n Ima stickin to it

John T

Well, it doesn't have lights so I don't have to worry about burning those out...

I was jumping the starter directly.. I read in another thread about how to jump a 6v system with a 12 battery (go direct to the starter)..

Now the monkey wrench.. It has a magneto.. and I've never owned a vehicle with one.. even our 63 galaxie had a distributor with a generator so a mag is completly new to me.

I found a book on the magneto listed on ebay (sold through someone who makes/sells dvd on rebuilding and tuning up a farmall H).

I see if I can trace the wires around and see what is connected to what. I know its not exactly stock though but it does still have the ammeter. The run/stop switch is now a toggle switch (up is run).. The starter switch is a low amperage switch that is connected to a starter relay. The wire from the battery to the relay is a normal 12v car type but the wire from the relay to the starter and the wire from the battery to the chassis are the bigger wires. I plan on changing those and I'd like to put in the orig style starter switch and run/stop switch.

From what it sounds like, since it had a 6v battery in it before it is more than likely still 6v and not 12v and the polarity can be either way other than the ammeter would read backwards which is an easy fix.. flip the battery around or fix the wires at the mag, regulator and ammeter.

~Mark

New and important data!!!!
Mags have no electrical connection to the rest of the system.
The wire from it goes to the Toffle you indicate, but from there it must go to ground only!!! The mag is self powered, and putting voltage to it is going to let smoke out. I will do a diagram here in a minute. JimN

Here is a diagram for the regulator equipped (three position Farmall with a MAG. With credit to Bob M for the original. JimN

OK, you can STILL figure this out. Get "the numbers" off the generator and regulator. One or both will tell you 6/12V, and the regulator no. MAY tell you neg/ pos ground. I say "may" because some replacement regulators were built for either.

Try to find anything that will provide a 12V load--that should give you something for the ammeter to "work with" so you can determine polarity.

If the part no. for the regulator is for EITHER polarity, in the end you can use whichever ground you want, and just repolarize the generator, and then swap terminals on the ammeter

This is why I'm going to hell. I've made a deal with the devil, that when I get down there, I'll be in charge of all the engineers--you know, the ones who couldn't "standardize" this kind of stuff. Worse yet, there exist some old 12V trucks that are positive ground. Who thought THAT was a good idea? We SHOULD have gone the way of aircraft--28V

That diagram from Bob M. looks close. Our regulator only has one bat output and it goes directly to the ammeter. Also, ours has a starter solenoid on it which I know isn't stock.

here is a crude drawing of what our wiring looks like. I didn't mark + or - on the battery as that is what I'm trying to figure out.


The only writing on the generator is...
Anderson Ind
Delco - remy
101355 8b13
model sn

the regulator just says Delco Remy made in the usa and on the bracket of the regulator it say 766. There are 3 connections on the regulator.. Gen, + and Bat. Gen goes to the A terminal on the generator, + goes to the F terminal and the Bat goes to the ammeter.

Assuming the solenoid is a 6v positive ground type, I'm thinking we should be using a positive ground batter hookup since what we have is close to the Bob M. diagram.. the principle is the same, just the added solenoid.

~Mark

The solenoid is correctly wired, and just fine.
If the Voltage reg in not marked for polarity, (and the sizes of the original cables in the Battery box were small to hot, and Big to ground) it can be setup to be pos ground (and probably was. I would jump the Bat terminal to the Arm terminal on the regulator with it not running (it will spark) then start it with a good 6v pos ground. JimN

If the tag on the generator is black, it is 6 volt and + grd. If it is red , it is 12 volt & ground may be either + or - .

The tag on the generator is silver and there is no tag on the regulator, its just stamped.

Thanks everyone for all the help.. at least I now have an understanding of how it is supposed to work. The wiring is pretty simple on this tractor. Its just new technology to me... (magnetos and + ground). I'm starting to understand this tractor.. and I'm really jonsing to get this thing running so I can take it out.

~Mark

Jim---shouldn't the start switch be originating from the hot terminal on the battery instead of going to ground?

Run switch also??

Scratch that last comment. Missed that it was a mag.

Maybe, but it is working now and that is the way he drew it up. Who knows what relay he (or someone) put on it. I decided to ignore it. Jim

(quoted from post at 04:00:22 04/01/09) Jim---shouldn't the start switch be originating from the hot terminal on the battery instead of going to ground?

Click to expand...

That still confuses me too.. I just can't get my head around a negative triggered 6v starter solenoid. Assuming thats what it is (6v negative triggered relay) then as far as I can tell its wired right..

It "was" a running tractor until is was parked a few years and then someone tried to start it, couldn't and then I got it. From what I gather, not much was done to try to get it to start and from looking at the condition of the wires/dirt etc that solenoid has been on it for years..

~Mark