SWD9 battery ground

[Mtjohnso]

Have a SWD9 that the battery needed charging. Pulled the battery out and charged it. Went to put it back in and I am wondering if this is positive or negative ground. Got out the manual and it indicates that it is positive ground.
Except when I go to put the cables back on the battery its clear that positive post of battery was connected to the starter and neg post went to ground. That observation is based on the diameter of the battery posts and the diameter of the cable clamps that go onto the the battery.
This tractor has a 12 v battery and not 2 6V batteries.
It has been started and run many times.
So are ALL SWD9 positive ground?
I would think to run with negative ground the starter would need to be changed.
I suppose I could hook it up negative ground and try the starter. If wrong the starter would run backwards and never engage.
Thoughts?

 

[used red MN]

Does it have a generator or alternator? If it has an alternator it needs to remain negative ground. A generator can be polarized to match polarity, however if at some point the battery was installed negative ground when it was previously positive and the generator was polarized to match the ammeter would register backwards, showing a discharge while the system is actually charging. The position where the armature brushes are placed in relationship to the field coils of the starter is what determines direction a DC starter motor turns regardless of polarity. A permanent magnet DC motor such as found on an automotive blower fan or a battery powered toy will reverse direction in relation to polarity.
The coil wiring should match polarity as well. Negative ground, positive feeds coil plus. Positive ground, ignition connects to negative primary of coil.

Edit to add: If it original generator is still being used and the polarity was intentionally switched at some point then the ammeter leads can be or could have been switched side to side which will allow it to register charge or discharge properly. The same process is used when an alternator is installed. Also I should add this warning, if the unit has been equipped with an alternator and you attempt to connect the battery positive ground the alternator will be a direct short and something will be damaged.

This post was edited by used red MN on 10/04/2023 at 05:41 pm.

 

[rustred]

Its pos. Ground from factory. To check yourself look at the coil wires. Pos. Ground has the positive wire going to the points. The rest comes after., meaning ameter and such. I dont write novels. Pretty much all this 1950 stuff was pos ground. Till the 60 series came out.

 

[rustred]

And for the starter it could care less how its hooked up it will only turn one way being the right way.

 

[w-9 nut head]

(reply to post at 16:28:23 10/04/23)

he starter doesn't need to be changed it's only going to spin in one direction.

 

[caterpillar guy]

Our MD was negative ground from the beginning was 12 volt with 2 sixes in series. It is a 1950 model. I thought all the diesels were 12 volt and negative ground. As for the coil wires that would work on a gas not so well on the mag on the diesels. Our MD also has a mag. IF it charged when it was hooked up negative ground in the past then I would hook it back up the same way. IF it didn't charge then I would look at which way the generator is and if an alternator then most likely it is negative ground. I would 60-70 years later doubt you could go by the book on this unless the previous owners that had it was meticulous about maintenance and keeping things original.

 

[BarnyardEngineering]

Long story short, it doesn't matter. The tractor will start run and charge either way, so long as the generator is polarized for the way the battery is grounded.

If the cables fit the posts for negative ground it's negative ground. The only way you can hurt something is if the tractor has an alternator and you hook it up POSITIVE ground.

 

[John T]

Mornin mt, you ask: I would think to run with negative ground the starter would need to be changed. I suppose I could hook it up negative ground and try the starter. If wrong the starter would run backwards and never engage.

Thoughts? Sure, here goes lol

1) The starter will still turn the SAME DIRECTION at either polarity

2) If its an original generator charging system IT CAN STILL CHARGE AT EITHER POLARITY once properly polarized..

3) If polarity was changed from original factory POS ground over to NEG and it has an ammeter, it would register bass ackwards.. How is it registering now ??? Maybe its leads got swapped ??

4) If polarity was changed from original factory POS ground over to NEG and it has a battery powered coil distributor ignition, it can still work at the incorrect (swapped) polarity HOWEVER its best if its leads are swapped over to match the battery polarity.

If the coil and ammeter leads are at the original polarity and working properly (ammeter registers correct) I would re install the battery at the original polarity BUT POLARIZE THE GENNY BEFORE START UP. The CORRECT coil polarity for POS ground is the - gets power from ignition switch and + goes to distributor. For NEG ground the coils + gets ignition switch power and - goes to distributor HOW IS IT WIRED NOW ???

How the ammeter is wired and how its works (right or wrong??) and how coil is wired are indications of battery polarity.

Questions ??

John T NOT an IHC expert see if they agree or not ????