Model T on Positive Ground?

[KenJackman]

I am the new owner of a 1927 T Coupe. I was surprised to find it with positive ground. It seems to charge and start ok as-is. Should I just leave it or?

[Jerry VanOoteghem]

No. It should have a negative ground. You may need to reverse the leads on the back of the ammeter for it to read correctly.

[Moxie26]

Is your ammeter showing a negative or positive reading?...either charging + , or discharging - . ???

[TRDxB2]

I am the new owner of a 1927 T Coupe. I was surprised to find it with positive ground. It seems to charge and start ok as-is. Should I just leave it or?

The real question is why is it on positive ground. Has some electrical component change caused it (engine, starer, generator/alternator, add a distributor, etc..) Model A's are positive ground maybe ..... Pictures of the frame & engine are needed to confirm
I wouldn't change anything until you understand why its positive ground. Also can you show the battery hookup to the frame

[Scott_Conger]

Negative ground is "correct"

if your car charges OK and your ammeter works properly, then the car has been wired to accept the "wrong" installation

if the above is true, then don't worry about it

welcome to the hobby

[Mark Gregush]

Model A's and Fords up into the 50, that were 6 volts were positive ground. If everything is working as it should, leave it. Would not be the first or last time it has been done.
But! If you do want to change and has the standard mechanical cutout on the generator, all you would need to do is swap the amp meter wires, swap the battery cables and flash the generator. Should note that the terminals on the battery are different size so would need to reconfigure them a bit for good connection.

[su8pack1]

I just converted my Model A back to positive ground after changing it to negative ground many moons ago. Couldn't remember how I did it. Found this on the web then remembered that's how I did it the first time. Haven't tried it on a T.

[Scott_Conger]

a standard, or electro-mechanical cutout doesn't care which polarity is ground...a diode cutout does

In my opinion, until the new owner knows everything there is to know about this car, it is best left alone if everything is operating properly. If for some reason it had, lets say, a Fun Projects Model A voltage regulator, then jumpering across it to flash the generator to negative ground would destroy a valuable and rare VR. For all we know, this has an alternator and swapping the battery around now brings another set of troubles.

this car is setup "wrong" but there has been no indication that anything needs "fixing", and jumping into fixing a "T" electrical system without knowing anything about it is a recipe for disaster.

So, Ken, enjoy your car...learn about it...buy the "T-1" Service Manual from any vendor and proceed cautiously and slowly with any repairs as they become necessary. In a year or two, you will be very glad to have tempered any desire to fix things before they break.

[Been Here Before]

The best advise is to make a Note to Self that you car is set up as "Positive Ground."

As long as the battery stays charged, fine. The generator and the magneto are separate and do not interact....that is unless there is a short at some time.

If your magneto is operating, start the car on battery, and switch to the magneto.

Now for the TMI - To Much Information:

Should you want to revert to the factory setting of "Negative Ground," make certain that you reverse the battery, negative terminal to chassis ground and the Battery Positive to the starter/generator terminal.

"Polarizing a generator is telling the gen. how the battery is hooked up. Positive or negative ground. It is done by using a short piece of wire and touching the post coming out of the generator(which is connected to one side of the cutout switch, and holding the wire to the other side of the cutout switch, for about 3 seconds. You will see a slight spark when you first touch the terminals. The wire on the other side goes to the battery and thus the generator sees which way current needs to flow."

The best advise here repeat. Keep as found.

[speedytinc]

What about the starter?? How was it modified?

[Jerry VanOoteghem]

What about the starter?? How was it modified?

It wouldn't need to be modified.

[Luke]

I am the new owner of a 1927 T Coupe. I was surprised to find it with positive ground. It seems to charge and start ok as-is. Should I just leave it or?

Ken,

It will likely carry on happily like this for the rest of its days.

That said I would change it to negative ground, and although you don't say what voltage it is presently I'd also change it to 12V if/when the 6V battery died.

The reasons for this are simply that 12V -ve ground is the modern convention; it is what everyone is familiar with, it's what everything is made for today (radio, GPS, charger etc), it won't affect the look of the car, and the coils will typically run better (on 12V). Here in my country 12V batteries are also less than half the price of 6V and suitable conventional or LED lamps are much easier/cheaper to obtain.

Despite the above you'll possibly soon become aware that this is a controversial subject here, along with several other things. No doubt you'll make your own decision, but I write from experience and fundamental reasoning so that you have an understanding and explanation of why I mention these things, not to invite an onslaught...

Luke.

[Scott_Conger]

Question: how many responses to an electrical question does it take to advise an owner to switch to 12V?

Answer: in this case, due unusual restraint, 11 posts

With 4 cars in the barn and in the hobby since 1976 I'm still waiting for that inevitable and irresistible urge to switch to 12V to hit me. Alas, the obvious need to switch doesn't strike everyone with the same urgency, and fortunately, my ability to enjoy the hobby is not dependent on the price of a new 6V battery every 6 years or so.

[Wayne Sheldon]

I agree with almost everything said already, especially the "as long as it is working fine, leave it as is for now". Just keep it in your head, know that it isn't quite right as is. And then, maybe later, when you are more comfortable with the car and how model Ts work, maybe then correct it.

A bit of history about maybe why it is this way.

Ford for the model A decided to go with positive ground. And believe me, electrical engineers have been debating that issue for well over a hundred years, and still do not all agree on which way is best!
In the antique automobile hobby, in the 1960s, most older mechanics had been remembering that "older Fords" were positive ground. They knew model As and early V8s into the mid 1950s were positive ground, and they just assumed that the model T was as well. When I was growing up and becoming interested in antique automobiles including model Ts, I heard it a hundred times from old mechanics. "Old Fords are positive ground. Almost everything else was negative ground, but old Fords were POSITIVE ground!"
For that reason, in the 1960s and 1970s, literally hundreds of model Ts were switched to positive ground. Simply because old mechanics "remembered" it incorrectly.
However, it doesn't really hurt anything. No need to change it back until it is either convenient due to needed repairs or other things being done anyway.

Welcome to the hobby! Model Ts have an almost magical way of connecting their caretakers to history, both general and personal.

[Been Here Before]

Ford, for what ever reason, was using Positive Ground even into the 1960s. This 1961, F250, 292 four speed has 12 Volt Positive ground. And it came with no power steering, power brakes, no seat belts, one visor on the drivers side. No air condition...just hand crank windows, window vents, and kick panel air vents. Heater was an option. A step up from a TT.

[KenJackman]

Thanks to everyone who has replied. You guys are all an incredible source of information. The car was restored about 10 years ago and has essentially sat undriven since then. It has been converted to a distributor and retains a 6v system. With the key on, before the engine is started, the ammeter reads in the negative. When the car is started and running, it reads in the positive. The positive lead is a braided cable and goes to ground on the frame. I changed the spark plugs this morning and the motor now idles and accelerates well for a 96 year old car. The transmission bands were replaced a week ago (kevlar) and it is my opinion that they were adjusted extremely loose….next project![image][image]

Motor 1

Motor 2

car

[/image][/image]

[Scott_Conger]

WOW!

nice buggy...congratulations

[KenJackman]

Thanks..I have been in negotiation with the previous owner for almost nine months before we finally put the deal together!

[Luke]

Question: how many responses to an electrical question does it take to advise an owner to switch to 12V?

Answer: in this case, due unusual restraint, 11 posts...

Scott,

With a degree of amusement, I wonder if you could point me to any posts on this thread where someone advised Ken to alter his vehicle to 12V? Certainly it wasn't me, I even emboldened the "I" in my comment and provided an explanation of why, and at what point, I would go that way

Ken,

I agree with Scott, it's a very smart looking vehicle, one of the better body shapes too, in my view.

Luke.

[KenJackman]

Good morning guys. Happy 4th to all!

I don’t have any intent to swap to negative ground nor convert it to a 12v car. “If it is working, don’t screw with it” The question on the positive ground came from my understanding that the entire run were negative ground cars. My post was just a question out of curiosity.

The engine turns over slower than I would like when cranking and the battery is of unknown age so I am just going to put in a fresh new Group 1 6v battery this morning….positive ground.

[Art M]

Clean all wiring connections between the battery and the starter. And make sure these wires are large enough.

I find that a 6 volt group 1 battery easily starts my stock 1923 touring car. This is after I cleaned connections and the starter switch.

Art Mirtes

[John Codman]

To Been here before : That is a beautiful 1961 Ford pickup, but when it left the factory it was negative ground, as were (and are) all American 12V electrical systems. You will have to go to the Brits to find a factory 12V positive ground electrical system.

Edit: Ford switched to 12 Volts negative ground for the 1956 model year.

[Scott_Conger]

Ken

a frequent fault on (even restored) "T"s is that the starter was never properly repaired, and the battery cables are far too lightweight. 1/0 cables at the very minimum are what you want. With a fresh battery, a new starter, and hefty cables, the car will crank over briskly.

As a new owner there are lots of things to learn and it is pointless to try to offer much more than this: buy the T-1 manual from one of the vendors, and never, never, ever, never try to just pull the starter out of the car. The bendix must be removed first or you will end up damaging any remaining portion of a magneto which may (or may not) be in the car. Since you have a distributor, the magneto might not be there, but if it is, there is no point in damaging it when removing the starter.

Have fun

[Jerry VanOoteghem]

The transmission bands were replaced a week ago (kevlar) and it is my opinion that they were adjusted extremely loose….next project![image][image]IMG_5132.jpegIMG_5275.jpegIMG_5276.jpeg[/image][/image]

It's proper to install Kevlar bands loose. That said, they still need to be able to do their job. They'll take a little while to finally settle in, after several small adjustments, then hold their adjustment for many thousands of miles, still being somewhat loose but able to work without slipping. Having a "high pedal" is not what you want with Kevlar bands.

Beautiful car by the way!

[TRDxB2]

Others need to way in on this but looking at some of the wiring I'm thinking your identification of it being positive ground is correct based on the pictures provided. So if you or someone else would change things its good to know what you have and what would need to be changed.
1. The cut-out on the generator appears to be a Model A cut-out. They usually have an extra set screw on the end connected to the generator post. Model T' cut-outs didn't have that . But you never know- need to follow where the yellow wire with black tracer goes.
--

--
--
2. The wiring for the distributor (Texas T?) appears to be consistent with positive ground but hard to confirm from the wires around the coil and where they go. The wire (green) running from the coil to the distributor condenser & zip tide to spark plug wire appears to be in a white harness wrap.
So while the chassis may be positive ground, some things may be wired to the positive terminal of the battery and not relying on the ground
--
--

Texas T Dist instructuios.pdf

(783.33 KiB) Downloaded 56 times

[KenJackman]

The transmission bands were replaced a week ago (kevlar) and it is my opinion that they were adjusted extremely loose….next project![image][image]IMG_5132.jpegIMG_5275.jpegIMG_5276.jpeg[/image][/image]

It's proper to install Kevlar bands loose. That said, they still need to be able to do their job. They'll take a little while to finally settle in, after several small adjustments, then hold their adjustment for many thousands of miles, still being somewhat loose but able to work without slipping. Having a "high pedal" is not what you want with Kevlar bands.

Beautiful car by the way!

Both the low gear and brake pedals travel to the floor. Low gear is clearly slipping and the brake has very little effect even at modest speeds. The brake pedal also travels completely to the floorboard. Reverse seems ok.

I have all the available manuals for the car and I can follow directions so this should be pretty straightforward

[Jerry VanOoteghem]

The transmission bands were replaced a week ago (kevlar) and it is my opinion that they were adjusted extremely loose….next project![image][image]IMG_5132.jpegIMG_5275.jpegIMG_5276.jpeg[/image][/image]

It's proper to install Kevlar bands loose. That said, they still need to be able to do their job. They'll take a little while to finally settle in, after several small adjustments, then hold their adjustment for many thousands of miles, still being somewhat loose but able to work without slipping. Having a "high pedal" is not what you want with Kevlar bands.

Beautiful car by the way!

Both the low gear and brake pedals travel to the floor. Low gear is clearly slipping and the brake has very little effect even at modest speeds. The brake pedal also travels completely to the floorboard. Reverse seems ok.

I have all the available manuals for the car and I can follow directions so this should be pretty straightforward

Yup. That's too loose then. As I stated, "...they still need to be able to do their job."

[J1MGOLDEN]

Has anyone ever found a reason for the Ford change from a negative ground to a positive ground?

I have not, but then I have been only working with Model Ts for a little more than 40 years now.

[Luke]

Has anyone ever found a reason for the Ford change from a negative ground to a positive ground?

As I recall there was a thought it might affect corrosion (in a positive way! , but it didn't live up to expectations.

I have to say that's from my rather hazy memory, the reality could be quite different, no doubt someone will know better.

Luke.

[Been Here Before]

""As I recall there was a thought it might affect corrosion (in a positive way! , but it didn't live up to expectations.""

In 1922, the Electrical Journal for December (p. 523), has a discussion that telephone systems using dry cells were able to reduce corrosion if the polarity was reversed -- positive was the ground. Too automobile manufactured thought the reversal to positive ground would reduce miss firings. But the change (1922) was not accepted by many.

[DanTreace]

Has anyone ever found a reason for the Ford change from a negative ground to a positive ground?

I have not, but then I have been only working with Model Ts for a little more than 40 years now.

Prior discussion was because gasses of bubbling electrolyte, from the storage battery upon charging/discharging, corrosion tends to collect at the positive terminal on the battery, causing poor connection and reduced voltage.

Ford engineers decided to ground the positive terminal of the battery to the frame, to minimize corrosion that would form on the battery positive terminal. Interesting fact is inside the storage battery, electricity flows from the negative plates to the positive plates, and externally from the positive terminal through a circuit to the negative terminal.

So using a absorbent pad or covering the positive terminal of a wet-cell storage battery with vaseline will help prevent such corrosion. Or....use the sealed Optima battery! No out gassing!


Period No Krode brass cover with wool pad soaked in vaseline.

[Mark Gregush]

Has anyone ever found a reason for the Ford change from a negative ground to a positive ground?

As I recall there was a thought it might affect corrosion (in a positive way! , but it didn't live up to expectations.

I have to say that's from my rather hazy memory, the reality could be quite different, no doubt someone will know better.

Luke.

Dodge started out negative ground but when the horn button was moved from the door to the steering column, they changed to positive ground. It was about corrosion.