Reverse Polarity - What is the damage

[mireland]

HELLO - This is my first post!

Hello everyone,

Before diving into my questions, I wanted to share something personal in case any of you knew my dad, Dave Ireland. I believe he was known here as S561. Sadly, he passed away on September 17th after a courageous 5+ year battle with cancer.

He often spoke highly of the MTFCA forums and the family of Model T enthusiasts here. He learned so much from all of you and was proud to contribute when he could. This spring, I’ll have to show you a picture of the monster MTFCA sticker he proudly placed on his toy hauler!

In 1961, my dad (11) and his dad bought this car from the original owner. They spent 3 - 4 years refurbishing. Now, his 1926 Touring, toy hauler, boxes of parts, and every MTFCA magazine he ever received have been passed on to me. I’m grateful for this legacy, but I already find myself missing the ability to call him for advice. So, I’m reaching out here, as he suggested I should if I ever needed help.

Background

The last time my dad drove the T was in August 2019, for about an hour. Before that, it was regularly on tours and trips, but we believe 2018 was its last active year. The car hasn’t been on a trickle charger since 2019.

After receiving the car, I did some basic maintenance: replaced the battery, changed the oil, flushed the water, replaced the fuel, and gave it a try. Amazingly, it started within just a few attempts. Since then, I’ve driven it 7-8 times, usually 2-4 miles each trip. It runs smooth, as far as I can tell.

The Battery Issue

After 3-4 small jaunts, the first new battery went dead. I assumed the generator might not be charging it enough, or that my short drives weren’t sufficient to recover the battery.

I tried charging the battery, but a tester showed a bad cell, so I replaced it with another new battery. Again, the car started right up and ran great. My 17-year-old and I had a blast taking turns driving it for over an hour around town.

Unfortunately, when we got home, I realized the battery had been installed backwards (reverse polarity). I removed the battery, tested and charged it, and it seemed fine afterward, but I’m not sure if this caused any damage to the car, the battery, neither, or both.

I then reinstalled the battery (this time with the correct polarity) after about 24 hours on a charger. Within 48 hours of being reinstalled, that battery was completely dead as well.

Questions

1. Could driving the car with the battery installed backwards for an hour or two have caused damage to the generator, electrical system, or anything else?
2. Before installing another new battery, should I do any troubleshooting to pinpoint a potential issue, or is it safe to assume it was just a battery problem?
3. I noticed a small brass piece at the back of the generator. What is it, and does it play any role in this situation? (.)

I’d greatly appreciate any advice on how to proceed—whether to test the generator, check for shorts, or just monitor the next battery closely. Thank you for taking the time to read this and for any guidance you can offer.

[speedytinc]

The brass thingy is an oiler for the rear armature bearing. Normal rebuilds use sealed bearings, making the oiler only cosmetic.
You might need to re-polarize the generator. Does the ammeter show a charge when running?. When you have it running, you can check the generator with an analog volt meter @ the gen output terminal. You can check output amperage with an analog ammeter between the cutout & the hot wire running to it.(big yellow wire)
Your fresh battery should not have gone dead. Check for a spark when replacing a battery cable to its terminal.
If so, there is something draining the battery.

[mireland]

I suppose, I should confirm with all of you. My assumption is the negative battery post is what should be connected directly to the chasis and the positive is what runs to the starter switch and other forward items to the car. I will look for 1926 touring wire diagrams shortly, but thought good to validate my assumptions along the way as well...

[Humblej]

Yes, negative ground.

[Scott C.]

Running with reverse polarity should not hurt anything. While doing so, your amp gauge will read backwards. I would look at the cut out. It might be sticking and running down your battery. It should only be on when running. Try disconnecting the battery when not in use and see if it holds charge.

[JTT3]

Matt before you try to reverse polarity at the generator please disconnect the battery in the car and then remove the cutout on top of the generator. Take a picture of the bottom of the cutout & post it here. You may have a voltage regulator and flashing it will cause problems with it operating. Don’t ask how I know. Folks here will be able to see what you have and may save you from destroying it.
If the bottom looks like this it’s a Fun Projects voltage regulator. Don’t flash it.


Best John

[TXGOAT2]

Concerning the battery, charging it it backwards (If that's what happened) is possible and is not good for it. Usually, a reverse charged battery can be saved by allowing it to completely discharge, then charging it correctly at a low charge rate. If the battery is charged correctly, connecting it properly should cause no problem unless the generator polarity is reversed, which it may well be. Polarizing the generator is not difficult. For a battery to be charged with reverse polarity, it wold have to be completely discharged to begin with.

[DHort]

I do not have his number, but if you call Ron Patterson, he will walk you through checking and fixing your setup. He did the same for me when I installed the battery backwards.

[George House]

I’m gonna jump in with Scott. Pop the top off your cutout. Theres a set of points there. With power coming from the wire to the cutout, those points should not be closed. If they are, thats drawing down your battery when the engine is off.

[John.Zibell]

Here is a link to Ron Patterson's schematic. viewtopic.php?f=2&t=21799&p=167775&hili ... ic#p167775

[J1MGOLDEN]

The $64 question is what difference does it make whether your car has a negative ground or positive ground?

Either way, I have flashed the generator field and everything worked fine.

The Model T was always negative ground.

Every Ford after that has been positive ground for some reason or purpose that I have never been able to find.

It took me years just to find the correct battery cable size and Ron found that for me.

Maybe he knows about polarities too!

[TXGOAT2]

I don't know why some are negative ground and others positive. Ford went to positive ground in 1928 and stayed with it through 1955. Older Packards are positive ground, and I think old Mopars are. Lug nuts vs Lug bolts?

[mireland]

All: thanks for the prompt and detailed responses. I look forward to the help and some day helping others….

Here is a picture for John. Not sure what this means…. lol

[Allan]

Matt. That's not a Fun Projects voltage regulator. It is an A model cut-out. Next question, does it matter if a cutout for a positive ground vehicle, a model A. is installed on a negative ground vehicle, a model T?
Allan from down under.

[John Codman]

I don't know why some are negative ground and others positive. Ford went to positive ground in 1928 and stayed with it through 1955. Older Packards are positive ground, and I think old Mopars are. Lug nuts vs Lug bolts?

Every 6V Mopar that I have ever seen was positive ground. I don't believe that there has ever been an American car or light truck that was 12V positive ground, but I have seen a few British cars that were. Mopar also used left-hand threads on the left side lug nuts or bolts (I can't remember which they used). Buick, Oldsmobile, and Pontiac did the same.
Buick uses lug bolts (technically capscrews) for years.

[Scott C.]

As long as it is a point type cutout, it will work. It is the diode type that only allows current to flow in only one direction.

[mireland]

TEAM UPDATE!

Thank you to all that pitched in with ideas! I have identified the problem, learned about everything there is to learn about the electrical system of the Model T, and FIXED THE PROBLEM.

I took the cut-out off the car and on to the bench. Using a variable DC power supply found that the cut out was not closing until closer to 17vdc. Watching the video and a few others that were down that rabit hole, I learned how and started adjusting the cutout (bottom of spring). Later realized that I could either adjust it too high or too low but there just was not a just right. Next I realized that the top of the cutout "maybe" had an adjustment to bring the top point slightly lower and closer to the electromagnet. BINGO!! That enabled the adjustments of the "below the spring" to not be so extreme and enabled a nice cut-in voltage around 5.7 - 6.1 and a cut-out voltage between 4.2 - 5.2. Took around 5 - 6 hours but was actually fun (but no one else in my family realized the pride of figuring it out. Ya'll will .

Before this post, I didn't know if that was the generator or the starter . I certainly had no idea what a cut out was or how it worked. Then learned how it works, how to adjust it, and countless other things I learned along the way...

So, end result - no damage from the reverse polarity BECAUSE the cut out was not working... That also explains the drained battery that was swapped out that caused the reverse polarity... YEAH!

THANK YOU! I hope my ramble helps others with a future similar problem.
[image][/image]

[DHort]

Matt

Now you can teach the rest of us how to adjust a cutout.

Maybe even make a video for youtube.

[Art M]

Prior to having a laboratory quality DC power supply, I used 4 D cell batteries to set the cut in voltage. The cutout was about 5.7 volts. This worked well until a loose connection at the terminal block caused the generator armature to burn up.
Now I have to figure out how to rewind the armature. I don't know where mica can be obtained. The factory where I worked rewound their own motors. I should have spent more time in there. Most of the people working in there have passed away. Any advice will be appreciated. I do know that an alternator would solve the problem, but that's not why I drive and enjoy my model T.

Art Mirtes

[Art M]

I should have said cut in voltage was about 6.2 volts. The cut out resulted at about 5.7 volts.

Art Mirtes

[mireland]

Matt

Now you can teach the rest of us how to adjust a cutout.

Maybe even make a video for youtube.

This is the video that I learned from. He has two or three, but this one is the main one that I used.
https://www.youtube.com/watch?v=eFGJnSRRPYA&t=210s

This is the bench power supply that I got from amazon. it is VERY sensitive as I was wanting to be between 4.5v (cut out) and 5.5v (cut in).
https://www.amazon.com/gp/product/B0D91 ... =UTF8&th=1

I got things all put back together and tested great. I may take it off and do a video at some point, but it is no 9degrees F in my garage, so may be a few months before things thaw back out to get to that . I really hope the above information helps someone else.

[A Whiteman]

Thanks for this Matt, I found it very interesting.
As a summary - in your testing - can one of the 6V cutouts be adjusted to make it a 12v operation?

[mireland]

Thanks for this Matt, I found it very interesting.
As a summary - in your testing - can one of the 6V cutouts be adjusted to make it a 12v operation?

Im not sure about that. I dont think the 1926 generator gets above 7 or 8 volts...but not sure. Also, I do suspect you could "bend" the two areas in the above pic to have it cut in and out at higher voltages.....but no idea what that would do to the rest of the electrical system.

I have been a Model T owner for just about 7.........weeks..... . My late Dad and late Grandpa would know the answer to this....but for now....the MTFCA forums may chime in soon

Have a great day!

[speedytinc]

The cutout could be tuned for an 8v battery. I think you risk burning out the cutout windings @ 12v. I wouldn't risk it.
A diode cutout would be the better way.
A T generator will charge a 12v system with no issues. Just 1/2 the amperage output. 4 amps is a good setting.

[Luke]

Remember that the Ford generator is a current-based charging device, it will charge at a constant current up to a reasonably high voltage.

You also need to be aware that I*E=W, and that there is a power limit for the generator beyond which you shouldn't go. Thus while it may charge at say 10A/6V (60W) you shouldn't allow it to supply 10A at 12V (120W).

Finally, for the sake of your battery particularly, and your generator/wiring secondarily, consider using a proper voltage regulator. What you have here is not...

Luke.

[A Whiteman]

Good answers and explanations, thanks guys.