Positive or Negative Ground

[GWheat]

This Ford 4000 was converted to 12v at some point in time. The main issue is I don’t know how to tell whether it’s a positive or negative ground. Here’s a couple of photos I got this morning before the rain set in.
Any tips or ideas are appreciated.
Thanks

 

[RickB]

3 cylinder or 4 cylinder 4000? Alternator or generator?

 

[GWheat]

Good old 4 cylinder. Currently has a alternator on it. It’s wired, but that’s one of the issues that’s with the tractor. Or so I was told.

 

[RickB]

All but certain to be negative ground. There’s few alternators in the world set up for 12V positive ground and no good reason to use one on that tractor.

 

[Industrial Toys]

If you have an alternator, presumeably you don't have a seperate voltage regulator so, one less thing to consider for voltage and/or polarity.

 

[RickB]

If you have an alternator, presumeably you don't have a seperate voltage regulator so, one less thing to consider for voltage and/or polarity.

You could bump the starter with a positive jumper cable and see if the fan goes the right way.

Starters are not polarity sensitive.

 

[Industrial Toys]

Edited, so as not to give bad information.

 

[RickB]

It's a DC motor. If you put reverse voltage to it, it will spin backwards.

Not so.

 

[Industrial Toys]

I may stand corrected. BUT, I have never seen a brushed DC motor that would not go backwards with reversed polarity. It does make sense though. You change the rotor polarity and the stator as well, so end up the same. So, every motor I have played with has likely had a permanent magnet for the stator???

 

[GWheat]

Here’s a picture of the alternator fellas. Not the greatest picture. Raining and bit cold today.
Name on the bottom is Delco Remy

 

[ruffdog]

What side of the coil is the points connected to? If they are connected to the neg side, that means a neg ground. Positive side means pos ground.

 

[GWheat]

What side of the coil is the points connected to? If they are connected to the neg side, that means a neg ground. Positive side means pos ground.

Going to have to talk beginner talk here. Know nothing about wiring.

 

[RickB]

What side of the coil is the points connected to? If they are connected to the neg side, that means a neg ground. Positive side means pos ground.

Only true IF the guy that did the conversion was smart enough to change it. Las one I cleaned up the “installer” left the original 6v VR wired.

 

[ruffdog]

Only true IF the guy that did the conversion was smart enough to change it. Las one I cleaned up the “installer” left the original 6v VR wired.

If the tractor was running recently, it will show if the tractor is a neg or pos ground as ignition coils don't work too good wired opposite of ground.

If your car uses a negative ground and you have a coil with primary and secondary terminals, the primary winding is connected to the terminal on the coil that is marked “+” or “Bat.” This is the terminal that receives voltage from the battery. The primary wire is then coiled around the iron core and its other end is attached to the terminal marked “-“ or “Dis.” The voltage flows from this terminal to the breaker points inside the distributor. (Positive ground is the reverse.)

 

[GWheat]

If the tractor was running recently, it will show if the tractor is a neg or pos ground as ignition coils don't work too good wired opposite of ground.

If your car uses a negative ground and you have a coil with primary and secondary terminals, the primary winding is connected to the terminal on the coil that is marked “+” or “Bat.” This is the terminal that receives voltage from the battery. The primary wire is then coiled around the iron core and its other end is attached to the terminal marked “-“ or “Dis.” The voltage flows from this terminal to the breaker points inside the distributor. (Positive ground is the reverse.)

Tractor has been sitting for 7-9 years in a pole barn on a south Texas ranch.

 

[ruffdog]

Tractor has been sitting for 7-9 years in a pole barn on a south Texas ranch.

By now, who knows what the mice mechanics have done with the wires!

 

[RickB]

If the tractor was running recently, it will show if the tractor is a neg or pos ground as ignition coils don't work too good wired opposite of ground.

If your car uses a negative ground and you have a coil with primary and secondary terminals, the primary winding is connected to the terminal on the coil that is marked “+” or “Bat.” This is the terminal that receives voltage from the battery. The primary wire is then coiled around the iron core and its other end is attached to the terminal marked “-“ or “Dis.” The voltage flows from this terminal to the breaker points inside the distributor. (Positive ground is the reverse.)

That is a far more serious problem in theory than practice. I have seen coils that have been wired incorrectly and left for years if not decades. I would not consider coil polarity as a reliable indicator of a positive ground system in THIS example. I would be somewhat confident of coil polarity indicating a negative ground system. That might indicate somebody cared enough to swap the coil polarity.

 

[GWheat]

By now, who knows what the mice mechanics have done with the wires!

Yeah they are actually the main contenders of me getting the tractor. Dad told me a story about it. Said one day it was running fine, next time they went to use it didn’t turn over or anything. By that time my Pap was old and he didn’t have much use for it anymore on the ranch anyways. Was mainly used at that time to pick wild mustang grapes for wine. So from then on it sat. Then my aunt inherited it when my grandmother passed and her husband was going to “attempt” to fix it. Yeah right! He ended up buying a Mahindra and giving me the tractor for a trade of me cutting them a fire ring from some 42” pipe.

 

[GWheat]

Just check the picture. If the red wire goes to the + battery post and the heavy wire on the opposite side of the solenoid goes to the starter terminal, you have a negative ground system.

View attachment 585106

There’s no battery on the other side which is the main concern. Yes the black wire goes to the starter.
I do believe it’s negative ground and I’m assuming you’re correct. There just seems to be no sure way of knowing until you fire it up or have lights?

 

[GWheat]

Does the assumed negative terminal go to ground? Is it black?
Look at the battery terminals, the positive opening is slightly larger than negative.
You could also clean off the GM alternator and post the number on it.

Both wires are red which sucks. And there’s only one terminal hook up on the ends of the wires, other one was missing when I received the tractor. Which looks to be the ground. When the rain stops tomorrow I’ll pull a number off the alternator and have a spec search.