Rebuilt Generator installed: Higher the RPM the more discharge

[Theo]

Hey guys,

I recently had a problem with the battery on my car not charging and dying. The ammeter wasnt working at all with the old generator. I thought my ammeter was broken, so I put a new one in. Same problem. I tested the system, and I found that my generator needed a rebuild.

So I bought a rebuilt generator off of ebay, with a new cutout installed. I bought a starter from this guy before so I know he does good work. Now, Im having the same problem as before, but my ammeter is working, and at idle it shows about 1 to 2 discharge, the higher the rpm, the higher it goes. During regular driving its usually at about 20 discharge.

The battery will hold a charge for about 5 starts, then die. When I charge it up again, same thing.

Could it be that the new generator needs to be adjusted to my car, or could it be a bigger problem?

The battery is hooked up corrected. Positve is grounded to the frame (bare metal) and the negative cable runs to the starter. Both are the proper type wires as well. I never had a problem until the first generator went bad.

Thanks guys!

[steve s]

I wonder if the generator needs to be "polarized". Hang in there; pretty soon Tom or someone else who knows what they're talking about will tell you how to do that. You touch a wire across the cutout terminals, or something like that.

Alternatively, I wonder if you've got the ammeter wired backwards. Does it show discharge when you turn on the lights? This wouldn't explain why the battery doesn't hold a charge, unless you've got a bad battery too. It wouldn't be the first time in Model A lore when two things were wrong.

Alternatively alternatively, many of us who have tired of fighting it switched to an alternator, and never looked back. But, them's fighting words for some folks.

Steve

[JBR]

Theo,
Is the ammeter hooked up correctly or could the wires gotten reversed? Did you polarize the generator after installing it? Have you had your battery checked to make sure it is good? Have you checked the generator out put at the cut out with a volt or ohm meter to make sure it is putting out voltage? Things to check.
Good Luck,
Jon

[Pilotdave]

I don't think your problem with the new generator is related to the failure of the old one. You probably need to polarize your generator. With car not running, briefly connect the two cutout terminals with a piece of wire. This will ensure that the magnetic field in the gennie is correctly set for your + ground system. Let us know how you make out.

Here's some information from a google search on this topic:

Why do generators need to be "polarized"? Auto generators need some magnetism to get started. This "residual" magnetism remains in the Field pole pieces even after the engine has stopped.

The next time the generator starts up, the residual magnetism creates a small voltage in the Armature windings. Not enough to charge the battery, but enough to allow the Field windings to draw current. As the Field current increases, the pole pieces create even more magnetism. That makes even more voltage in the Armature, and the cycle continues until the
generator is capable of producing maximum output.

What happens though to a generator which has been stored a long time or is freshly built? The residual magnetism may have decreased to the point where it can no longer get the generator started producing voltage. In the case of a new generator or one which has been mis-treated, the residual may even be of the wrong direction (North and South poles reversed).

Polarization is a simple process used to restore the Field pole residual magnetism and ensure the magnetic direction is correct.

[Theo]

Thanks for the responses guys!

Originally Posted by JBR

Theo,
Is the ammeter hooked up correctly or could the wires gotten reversed? Did you polarize the generator after installing it? Have you had your battery checked to make sure it is good? Have you checked the generator out put at the cut out with a volt or ohm meter to make sure it is putting out voltage? Things to check.
Good Luck,
Jon

The ammeter is hooked up correctly. The battery was new this summer, and does hold a charge. It just looks like the generator isnt charging it.

I did not polarize the generator, atleast I dont think I did. I just disconnected the battery, disconnected the generator, took the old generator out, put the new one in, reconnected the wires, and re connected the battery. Was I supposed to do something else?

[Pilotdave]

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Theo, unless you polarized the gennie, it almost certainly needs to be done. The good news is that it's very easy to do. See post #4.

[Theo]

Originally Posted by Pilotdave

Theo, unless you polarized the gennie, it almost certainly needs to be done. The good news is that it's very easy to do. See post #4.

Thanks for the response! I will give it a try when I get home. Where exactly do I connect the wires? Im sorry for the stupid questions. Im 20 years old and the car was given to me by my grandfather, so Im still learning alot. I actually just drove it to my college class today

[Pilotdave]

Theo, your questions are fine - one reason we hang out on here is to be a source of information to those just getting into this hobby. You are a very lucky person to have your grandfather's Model A!

Look at the cutout on your generator. You'll see two wires attached to it, though you may need to remove a sheet metal cover to see the terminals to which they are attached. Once you have located those two terminals, take a piece of wire and touch the bare ends to each of the terminals - briefly. You may see a spark when you do this. The battery will be trying to spin the generator, so don't leave the wire on there more than a moment. Let us know if this needs more explanation, and don't worry about your questions - we are happy to help.

[Pilotdave]

One more thought. Your generator output is the opposite of what your battery wants to see. Running the engine this way might damage the battery - on this I am not so knowledgeable. Can you find a piece of wire where you are? You should be able to polarize that generator right there in the parking lot at your college.

[Tom Wesenberg]

As mentioned, that round can on the generator is the cutout, which is simply an OFF-ON switch, which disconnects the generator from the battery when the output voltage falls below battery voltage. The output stud on the Model A generator is connected to one cutout terminal and the wire leading to the amp guage is connected to the other cutout terminal. Simply jump those two terminals together for 1 second and the generator is polarized.

I wonder if the first generator didn't burn out due to a problem in the charging circuit, which consists of the generator, cutout, wire going to the terminal box, wire going to the amp meter, amp meter, wire returning from the amp meter to the terminal box, wire from terminal box to the starter switch, battery cable to the battery, battery, ground cable, and the car chassis and all ground connections., The frame and engine are part of the electrical path forming a complete circuit. Any interuption (bad connection) in this circuit can allow the generator to put out up to 40 volts, which will quickly burn up the generator windings.

Make sure the connections inside the terminal box are clean and tight. If you have a fuse (this is an aftermarket item) mounted to the starter switch be sure it has tight connections. They have a reputation for being loose and loosing contact.

[Theo]

Originally Posted by Tom Wesenberg

As mentioned, that round can on the generator is the cutout, which is simply an OFF-ON switch, which disconnects the generator from the battery when the output voltage falls below battery voltage. The output stud on the Model A generator is connected to one cutout terminal and the wire leading to the amp guage is connected to the other cutout terminal. Simply jump those two terminals together for 1 second and the generator is polarized.

I wonder if the first generator didn't burn out due to a problem in the charging circuit, which consists of the generator, cutout, wire going to the terminal box, wire going to the amp meter, amp meter, wire returning from the amp meter to the terminal box, wire from terminal box to the starter switch, battery cable to the battery, battery, ground cable, and the car chassis and all ground connections., The frame and engine are part of the electrical path forming a complete circuit. Any interuption (bad connection) in this circuit can allow the generator to put out up to 40 volts, which will quickly burn up the generator windings.

Make sure the connections inside the terminal box are clean and tight. If you have a fuse (this is an aftermarket item) mounted to the starter switch be sure it has tight connections. They have a reputation for being loose and loosing contact.

I think I might have found my problem. Before I took the generator off, the original cutout (square one) had both wires attached to one terminal. The one closer to the rear generator. When I re installed it, I hooked it up the same way. Are both wires supposed to go to seperate terminals?

[Pilotdave]

Theo, are you saying that there is a screw terminal on your cutout that has no wires attached to it? On the terminal with two wires.....does one of them attach to a spot on the generator? Or do both go to other places in the wiring system?

If one of those two wires attached to the terminal does attach to the generator, then the cutout can't function as the on-off switch that Tom described. The wire from the generator should be attached to one terminal and the second wire should be attached to the other terminal. Going by memory here but often the terminals are marked in some way such as 'Gen' and 'Bat' indicating that the first is connected to the generator, the second to the wiring harness.

[Theo]

Originally Posted by Pilotdave

Theo, are you saying that there is a screw terminal that has no wires attached to it? On the terminal with two wires.....does one of them attach to a spot on the generator? Or do both go to other places in the wiring system?

If one of those two wires attached to the terminal does attach to the generator, then the cutout can't function as the on-off switch that Tom described. The wire from the generator should be attached to one terminal and the second wire should be attached to the other terminal. Going by memory here but often the terminals are marked in some way such as 'Gen' and 'Bat' indicating that the first is connected to the generator, the second to the wiring harness.

The far left terminal (towards the pulley) has no wires attached to it. The terminal facing the back of the generator (towards the firewall) has both wires attached to it. Which wire should be attached to which side. As far as I know the cutout didnt have anything marked.

I thought something was wrong here, but I was just installing the old generator the same way my grandfather had it.

[Pilotdave]

Theo, if your wiring at the cutout is as you describe in #11, you don't need to polarize the generator. You do need to fix that wiring by connecting the wire from the generator to the other terminal on the cutout. You also need to reverse the wires attached to your ammeter posts as they are likely reversed. You can run the car this way but would want to fix this so the ammeter reads properly.

Here's what it sounds like could have been happening:

Your generator is essentially an electric motor. If you were to connect a generator directly to a battery on your workbench, the generator would spin just as a motor does. With your cutout wired incorrectly as you describe in #11, you have no switch to disconnect your battery from the generator when the engine is not running. Your battery would be trying to spin the generator whenever the engine is not running. This runs down your battery. With the engine running, you would be charging the battery though the incorrectly wired ammeter is telling you otherwise. However, your battery likely would be losing charge faster while the engine is off than you can recharge it while driving. So over time - and not too much at that - your battery will lose enough charge to no longer start your car. You could then recharge your battery and repeat the cycle.

[Mikeinnj]

A picture of the wiring on a cutout would be worth a thousand words here.....

[steve s]

Originally Posted by Theo

I think I might have found my problem. Before I took the generator off, the original cutout (square one) had both wires attached to one terminal. The one closer to the rear generator. When I re installed it, I hooked it up the same way. Are both wires supposed to go to seperate terminals?

Theo,

Let's see if this works.

There should be three bolts attaching the cutout to the generator. Two are simple attachment bolts; the third will have some insulating washers and is the actual output coming from the innards of the generator. This is one of the contacts that you use for polarizing.

On the opposite side from the generator output post, is a screw terminal on the side of the cutout can. This is the other contact that you use for polarizing. All of your wiring should go to this. With original color coding, this would be a yellow with black tracer going to the terminal box on the firewall (and from there to the ammeter), a yellow wire going to the horn, and a wire that is either yellow or (earlier) yellow with black tracer going to the light switch thingy on the bottom of the steering column.

Steve

[Pilotdave]

Theo, Mikeinnj has a point! I've been trying to locate a picture for you. But this might go a lot faster if you could take a picture of the cutout and generator that shows the wiring you have now and post it on here. The circumstances you are dealing with depend on the style of cutout and how its wired to the generator. In the meantime, I will go to my shop and look at the gennie I have there.

[Pilotdave]

Here is a photo of a generator with a cutout mounted on top.

You can see a wire from the generator body attached to one terminal. The other terminal (pulley side of cutout) has no wires attached to it as the generator is sitting on my bench. You would have the wire to the ammeter attached to this terminal. I don't think it matters which terminal is attached to which wire. Keep in mind that you may have more than one wire from the car's wiring harness attached to a terminal on the cutout as that's a convenient spot to pick up electricity for other purposes. Thus a picture of your setup would be helpful

[Theo]

here are some pictures for you guys

[Theo]

The yellow wire is coming down from the terminal box. The other wire there looks like its coming from somewhere by the lights. Its hard to explain for me hahaha