1951 B POSITIVE OR NEGATIVE GROUND

[AndrewG]

I've picked up a 1951 B that appears to have been set up as a positive ground. There was no battery in it when I picked it up so I can't confirm how the previous owner had it actually hooked up, but all wiring appears to indicate it was still being used as positive ground. However, it does have a multi wire 12V Delco alternator installed so it is raising some questions about whether it was fully converted the right way or not. What are some tips to check and make sure everything is properly connected and confirm positive or neutral ground regardless of cable colors? i am currently getting no spark, so of course investigating the distributor, but need to clarify the positive/negative ground before I make a final determination.

 

[Hay maker2]

Generator = Positive Ground
Alternator = Negative Ground

 

[AndrewG]

@Hay maker2 Thank you for that reply. This was also my immediate thought too. I had read where some people would reverse some things in the alternator wiring to make it work, but thought I'd check here. I'll check into swapping some things around later and see what happens. Thanks again. Just getting started into this Antique world, but ended up with 2 at the same time. 1950 late B and a 1951. Lots of similarities, but also several things changed between 11K serial numbers

 

[Jim.ME]

I've picked up a 1951 B that appears to have been set up as a positive ground. There was no battery in it when I picked it up so I can't confirm how the previous owner had it actually hooked up, but all wiring appears to indicate it was still being used as positive ground. However, it does have a multi wire 12V Delco alternator installed so it is raising some questions about whether it was fully converted the right way or not. What are some tips to check and make sure everything is properly connected and confirm positive or neutral ground regardless of cable colors? i am currently getting no spark, so of course investigating the distributor, but need to clarify the positive/negative ground before I make a final determination.

Clamps for the positive and negative posts of a battery are generally slightly different sizes when you check them, if they have been on the battery and tightened.. The positive post of a battery is generally a bit larger than the negative post. That can be one clue as to which was grounded.

Unless someone paid extra for a positive ground alternator (or had one built as positive ground, it is not a swap a couple wires change) it will be negative ground. I would say the chances of the alternator being positive ground are less than 5%.

 

[AndrewG]

@Jim.ME Thanks for the feedback as well. I'm thinking it was either partially converted or just incorrectly done. Unfortunately the previous owner is no longer with us, so you can't ask questions, just have to figure it out. It's just odd that it appears they left everything else as it would be for positive ground (coil connections, colors of cables etc......) but changed the alternator.

 

[Fixingfarmer]

2 nice little tractors it sounds like!

So negative if alternator

Do you have a coil? Probably should hook the feed up to the plus side. Not much else to check really if it has a mag it won’t care

Old incandescent lights don’t care either

Checking to see if it’s charging when done will tell you if you need to do anything interesting wiring wise

Consider an alternator light if it doesn’t have one? Someone else might remember something I’m not

Edit you do have a coil it sounds like your post hit when mine did

I think they will actually run opposite but I usually change them if I see them

 

[Jim.ME]

@Jim.ME Thanks for the feedback as well. I'm thinking it was either partially converted or just incorrectly done. Unfortunately the previous owner is no longer with us, so you can't ask questions, just have to figure it out. It's just odd that it appears they left everything else as it would be for positive ground (coil connections, colors of cables etc......) but changed the alternator.

First, DO NOT depend on any wire colors being right. I have seen original wiring that does not match a color shown on an OEM wiring schematic. Where the end connections land tells the story.

A coil will work either way so it will work even if they changed the battery groundand did not change the wires on the coil.

Lights will work either ground without changing wiring, fuses, or switches. If they did not swap the wires on the ammeter, it will read backwards, but it will not destroy it.

Very little has to change to convert to an alternator and have it work, if one doesn't care about making things look correct by all standards.

You should post some pictures of at least the alternator so we can be sure which "multi-wire" Delco alternator you have.

 

[AndrewG]

@Jim.ME @Fixingfarmer thanks guys. Your thoughts all match what I see and think. We just never know what these guys have done in the field over the years. I will get some pictures later this evening when I get back in front of the tractor.

 

[AndrewG]

@Jim.ME @Fixingfarmer photos of alternator and of both tractors

 

[Jim.ME]

@Jim.ME @Fixingfarmer photos of alternator and of both tractors

The one in your first picture is a three-wire, internally regulated Delco 10SI. The picture of the second one is not clear enough to see, but if it is the same it too would be a three-wire 10SI, like the first one.

 

[AndrewG]

@Jim.ME sorry for any confusion. It’s the same alternator just from both sides.

I just completely eliminated the alternator temporarily and fixed everything else like negative ground, installed and set some new points and it’ll run. Decided that was enough for tonight until my carburetor kit comes in (float sticks badly). I’ll permanently wire everything back up over the weekend. I do believe it was set up negative ground already, they just used the coil reversed. I think it’s a winner, the 20-30 seconds in ran seemed pretty good.

 

[AndrewG]

I should also note, my photos of the tractors above are actually two different tractors, not the same one from both sides. I just took the shots that were easy to get inside the garage.

 

[AndrewG]

The photos are kinda obvious if you look at details, but nevertheless just clarifying for anyone taking a quick glance.