MTFCA Forum

My generator seems to be charging too much. I don't want to burn it out or damage my battery. It is putting out 9.3V and 13A on the dash gauge at a high idle. I've moved the 3rd brush all the way away from the engine (opposite generator rotation) and it seem to make no difference. Am I missing something? I have a solid state cutout and a 6V battery. When I turn on the headlights it goes down to about 3A on the gauge.

your brushplate "null" is likely off...

https://modeltfordfix.com/adjusting-the ... patterson/

Hi James,
yes, Scott is correct. You have to find the neutral position on your brushplate.
https://youtu.be/C7Psk4hK3gU
See at 28:00 minutes.

Regards
Markus

Here is the link to the generator nuetral setting procedure.
https://modeltfordfix.com/adjusting-the ... patterson/
Ron

Thanks guys, I'll check that and see what I find.

Have you calibrated or compared your dash ammeter to a more accurate one?

This is why I just gave up and bought an alternator. A lot less of a headache.

It's too bad you think it's a headache... Part of the experience of owning a model T is doing repairs and learning.

Bill

I agree, and further, if you do the repair right, you rarely have to do it a 2nd time...generators and starters not withstanding

I have not used an alternator on my cars, however, it has been my observation, that many of the cars on tours break down with alternators. Some do not have the gear installed very well and it breaks off. Others have overheated because the alternators have been adapted from other cars which have a pulley with a fan attached which cools the alternator but when on a Model T, they tend to get too hot.
On the Redwood to coast tour in 2019, my generator quit working, but since the driving was all done in daylight hours, I only used the battery to activate the coils when crank starting and then switched to magneto, so the battery lasted the rest of the tour. Then when I got home, I installed another generator which I had in my shop, and it has worked fine ever since.
I even buy used generators at swap meets, usually for a low price, and swap parts to make one which works. Rarely do I need to do major work on a generator.
Norm

Norman Kling wrote: ↑

Thu Sep 16, 2021 10:00 pm

I have not used an alternator on my cars, however, it has been my observation, that many of the cars on tours break down with alternators. Some do not have the gear installed very well and it breaks off. Others have overheated because the alternators have been adapted from other cars which have a pulley with a fan attached which cools the alternator but when on a Model T, they tend to get too hot.
On the Redwood to coast tour in 2019, my generator quit working, but since the driving was all done in daylight hours, I only used the battery to activate the coils when crank starting and then switched to magneto, so the battery lasted the rest of the tour. Then when I got home, I installed another generator which I had in my shop, and it has worked fine ever since.
I even buy used generators at swap meets, usually for a low price, and swap parts to make one which works. Rarely do I need to do major work on a generator.
Norm

Right on Norm. If a guy has to have 12v, a T generator can be used. For preservation, just turn the output down 1/2.
The problem with a T generating systems it typically a cutout issue. How many cheap cutouts are responsible for a generator rebuild?
I see a lot & a lot of close calls.

well I had a chance to work on the T today and attempted to adjust the generator with the Ron Patterson method as he suggested. With car switched off the battery was at about 6.5V. I backed off the 3rd brush (opposite direction of rotation) and loosened the four screws holding the brush plate. With the engine running above idle I moved it back and forth while watching the Ammeter with a mirror. I never got it to go below 10A. Then I did the same thing with a volt meter (both digital and analog) and never went below 9V. Checked at the battery - 9V. I'm stumped. Moving the brush holder has no discernable effect that I can see. What am I doing wrong?

JamesD wrote: ↑

Sun Sep 19, 2021 8:54 pm

well I had a chance to work on the T today and attempted to adjust the generator with the Ron Patterson method as he suggested. With car switched off the battery was at about 6.5V. I backed off the 3rd brush (opposite direction of rotation) and loosened the four screws holding the brush plate. With the engine running above idle I moved it back and forth while watching the Ammeter with a mirror. I never got it to go below 10A. Then I did the same thing with a volt meter (both digital and analog) and never went below 9V. Checked at the battery - 9V. I'm stumped. Moving the brush holder has no discernable effect that I can see. What am I doing wrong?

Are you getting that reading @ the battery posts directly. The battery regulates the voltage it will take. Are you testing @ a possibly bad battery connection?
I dont know of a digital meter that reads correctly on a T. Even a Fluke meter. A 9V reading aint right. Get that figured out & retry the brush holder adjustment. If you cant get the output amps right, try removing generator & adjusting per the bench test lifted 3rd brush & gear rotation setting.

I tested the voltage at the generator post (both sides of the cutout) with an analog meter. I just tested at the battery to make sure I was getting similar voltage there in case there was some connection issue. It reads 9V with analog or digital meter.

Is it possible your car has an 8 volt battery installed?

No, it's definitely a 6V battery.

Does your car have a starter, and if so does the battery crank the car as it should? If you have a very weak battery, it may not "load" the generator enough to keep the voltage/current within an acceptable range. The Model T generator is designed to work with a full size, 6 volt lead acid battery that is in good condition with good tight connections at all points in the charging circuit. Does your car have 6 volt headlights? If so what happens to the voltage/current readings when you turn them on with the engine running at about 1200 RPM? (I wouldn't leave them on very long if the voltage reading stays over 7 or 8 volts, as they may burn out.)

I'm no sparky but the way the system is designed the battery is the regulator, it seems to me that in order to hit 9.3 volts, that means the battery is taking it, faulty battery?. I run 8 volt batteries is 4 of my stock charging system T's, none run voltage higher than what the battery allows, 8.2v.

Kerry

not entirely correct, though I see your logic and it's led you into a trap. The generator will generate until it overcomes the cutout, which on a 6V system is around 7.2V with a correctly adjusted cutout...depending on how the brush plate is adjusted, even greater current/voltage can be had, despite the battery being in the circuit. A generator run at correct test speed on a stand will be set up to put out 4+ amps (choose your poison) and depending on the condition of the battery, that can range from the cutout voltage (7.2V) to nearly 8V (or perhaps more). I inadvertently discovered some years ago that nearly dead battery hooked up to a test set will definitely allow the generator to put that out, while a fresh 6V battery will take the normal 7.2V and sometimes just a bit more (that was a bit of info I'd never read about or previously encountered until then). When the generator output drops sufficiently due to a reduced RPM, the current reverses and the battery is safely dropped from the loop at a voltage well above it's ambient state keeping the generator from motoring due to the points being forced open by spring tension and lack of magnetic attraction through the winding to keep them closed. For those that don't know, due to this phenomena, the cut out is correctly referred to as a "reverse current cut out".

Now, if the cutout was a DIODE, then the battery would be setting the "cut in" voltage...again, not so with a mechanical cut out.

Given all of the above, If the battery really is taking that voltage as the OP states, it may be more of a symptom of a dud battery than a malfunctioning generator (though there are no end to generator foibles after years of neglect and maladjustment).

I know you know all this, but think that you need to re-review the battery's status in the system...ie: it isn't entirely the limiting factor of the generator output.

TXGOAT2 wrote: ↑

Mon Sep 20, 2021 7:13 pm

Does your car have a starter, and if so does the battery crank the car as it should? If you have a very weak battery, it may not "load" the generator enough to keep the voltage/current within an acceptable range. The Model T generator is designed to work with a full size, 6 volt lead acid battery that is in good condition with good tight connections at all points in the charging circuit. Does your car have 6 volt headlights? If so what happens to the voltage/current readings when you turn them on with the engine running at about 1200 RPM? (I wouldn't leave them on very long if the voltage reading stays over 7 or 8 volts, as they may burn out.)

The car has a starter and cranks like a champ although I rarely use it. It starts easily with the crank and I enjoy using the crank. The battery reads 6.25V after sitting overnight. I have 6V headlights and I've driven about 5 miles with them on without them burning out. The current at the Ammeter reads about 3A at 25mph with the headlights on. As stated before, I have a solid state cutout.

Scott, like I said I'm no sparky but as you say the system can charge 8v or even more depending on battery condition would suggest that the bulbs would be at risk of blowing if the battery was low, I've set genny amps in my lathe after rebuilds and never had a voltage run out over what the battery is 6,8 or 12. My work shop battery charger is the same, volts are not monitored, works on what amps you put in the battery and the battery is the regulator.

Kerry, I did miss the part about "solid state". If you are not testing in the lathe with a voltage regulator, then I can see where the generator matches the battery. The reality of it is, is that a 6V mechanical cut out (of which I was speaking) only closes at 7.2 (or so) volts, so the battery most certainly is seeing greater than 6VDC. If on the other hand you are using a diode, then the generator will not measurably exceed the battery voltage to the extent that it is easily discernible with a voltmeter. I suspect you use a diode for testing.

Thinking more about the 9+ volts, makes me realize that reading is taken with a DVM with the engine running. You absolutely cannot trust a DVM to work accurately in the presence of a standard "T" ignition system...the 13A on the ammeter on the other hand, I do believe.

that generator is still maladjusted

James, since you did not have success by yourself adjusting it in-car, take the generator to someone who knows "T" generators and has an honest-to-goodness generator test set. Do NOT go to a modern starter/alternator shop or you will end up with a completely dorked-up generator for sure. They will not know what they are doing, but will never admit it or likely even suspect that they don't know what they're doing (those are the guys whose repairs come looking suspiciously like a roll of electrical tape).

The complaint is not particularly unusual and the exact same complaint is registered here, under the exact same circumstances, including running the lights and still showing 3A charge rate: http://www.mtfca.com/discus/messages/25 ... 1333591748

Scott.
I was taught a little different on the operation of a 3 brush cut-out than to think it was set at around 7.2 volts, the voltage involved in it's operation for the magnetic switch would close the points when genny voltage matches the battery voltage and open when the genny voltage drops to less than battery, therefor the battery is the regulator. One can drop in any voltage battery into a 3 brush system and the only thing it changes is the Amps on which one can adjust for.

Thanks Scott, but I don't know of anyone who knows anything about Model T generators around here. If you read my earlier posts you will see I have tested with an analog volt meter, not just the digital one I showed a picture of. I can read a meter and it shows 9.5V with the engine running at a higher idle. Is my next step to try to set the "null point" with the generator out of the car, or is there something else to check?

Kerry

by virtue of the tension on the cutout spring and gap of the points, you can make them pretty much (almost) any voltage engagement you want. The 6V cutouts are adjusted for nominal 7.2V and once the generator hits that, the electromagnet should overcome the tension of the spring and route current to the battery. Simultaneously upon completion of this circuit, the "pull in" coil ceases operation and the "holding" circuit takes over. As the genny speed reduces to a level where battery current wants to flow back at the generator, it bucks the cutout and it opens.

Yes, the battery is or should be when healthy, the ultimate determiner of voltage, but there has to be a threshold of when current flows TO the battery vs. when current flows FROM the battery. It is impractical to have that threshold at the razor's edge of 6 (6.3V), so the standard is 7.2V to MAKE the connection and somewhat lower output from the generator to BREAK the connection. You don't want to be anywhere near nominal in any direction or the device would dither like an old maid trying to decide what to do.

James

your best bet is now to buy the MTFCA "Electrical Book" and study some of the techniques used to "motor" the generator and "null" the generator. Nine times out of ten, you'll end up with a functional and adjustable generator..10% of the time it will fight you tooth and tong and drive you crazy. The book will also lay out repair techniques including how to repair the brush plate. A generator which will not respond to Ron Patterson's in-car adjustment technique often has bigger but fixable issues. Good Luck. Sorry it didn't work out quickly and simply for you.

Let me add some pertinent personal experience. One of the things I do is rebuild generators. I use the bench techniques & have a machine to test run with a built in cutout & ammeter. Setting the null directly to a battery.
Occasionally I reset on a customer car as part of general service. Sometimes the in car reset doesnt give the range or allow me to turn down the output to a minimum setting. If I remove & check the null, its usually quite off optimal. I reset it off car, reinstall & final 3rd brush adjusted while running. That gets it where I want it.
The excessive voltage still has me scratching. I have not experienced this with a mechanical or diode regulator/cutout.
Looking forward to the final answer.

Could this generator possibly have been re-wound or otherwise modified to provide higher voltage?

Pat

a T generator will give you any voltage you want. Until it melts down.

TXGOAT2 wrote: ↑

Tue Sep 21, 2021 3:32 pm

Could this generator possibly have been re-wound or otherwise modified to provide higher voltage?

That would be silly, but not impossible, I suppose. "Rebuilders" do some really dumb stuff sometimes.

Remember, the generator doest care or know what voltage to put out. When unregulated It will charge to a self destructive amount of extra voltage, If that regulation stops working, (defective cutout) the voltage go sky high 25v+ untill it over heats & slings armature winding connection solder breaking the electrical connection. When the battery comes out of the circuit. Broken connection, ammeter burned out defective cutout etc it doesnt take long @ speed to burn up. If you notice your ammeter stops showing a charge, better stop & ground the output terminal fast.

Hence a T generator will work fine for 6, 8, or 12V charging. The amp outputs should be backed down to prevent that extra heat. Unless you are driving a lot @ night or using a lot of starter motor, 3 or 4 amps is plenty for 6V. Rule of safety is 1/2 the amp setting for a 12V system.

A diode "cutout" will work with any of those voltages if high enough rated. It acts as a one way valve for electricity. The battery acts as a voltage regulator in how much it can accept & typically accepts less than 1V over its rating as set with an appropriate amp output, if the battery is good. Over charging is still possible. Set the output to just above actual need.
A mechanical cutout is typically rated @ 6-8V. One of my T's has one charging an 8V battery. If charging 12V, you would need one so rated. A voltage regulator, like F/P's made was specific to 6, 8, or 12v. V/R's take the excess voltage set above the battery to maintain a full charge & dump to ground, shutting the generator off in rapid cycles & can show up as a swinging meter needle. The F/P regulators read battery voltage & shut off output when fully charged like a battery tender.

Today I started the car, no chrging at all. First I checked the wiring at my switch. All OK. Checked the wiring between the generator and the terminal block to the ammeter - OK. Checked the wire from the battery to the ammeter - OK. I pulled the generator and set the Null point. It ran like a motor with the third brush pulled up and not contacting so I set it so it wouldn't run either way. reinstalled it with the third brush at the most retarded point. Started the car. no voltage. moved the third brush and I could hear it loading up. checked the voltage: 9.5V. moved the brush back to the most retarded position: 9V. Then my Ammeter stopped working. Doesn't move either way when I start the car, or when I turn on the headlights. $%$&%$#@!!!!! Now I can't even see what kind of Amps it's putting out. Guess I'll go to bed and try again another day.

The voltage measured at the generator will always be higher than at the battery because of the wiring resistance, plus a small voltage drop across the cutout. What ultimately counts is the voltage at the battery terminals, which should be about 7V on charge.
If the voltage at the actual battery posts is much higher than 7V with a few amps of charge, the battery is likely to have a defective cell.
Assuming you do have 7V at the battery, 2V drop between the generator and battery is a bit high and I'd be suspicious of the wiring and connections; particularly the connections at the ammeter, especially if it's a repro one with the plastic nuts.

JamesD wrote: ↑

Tue Sep 21, 2021 11:05 pm

Today I started the car, no chrging at all. First I checked the wiring at my switch. All OK. Checked the wiring between the generator and the terminal block to the ammeter - OK. Checked the wire from the battery to the ammeter - OK. I pulled the generator and set the Null point. It ran like a motor with the third brush pulled up and not contacting so I set it so it wouldn't run either way. reinstalled it with the third brush at the most retarded point. Started the car. no voltage. moved the third brush and I could hear it loading up. checked the voltage: 9.5V. moved the brush back to the most retarded position: 9V. Then my Ammeter stopped working. Doesn't move either way when I start the car, or when I turn on the headlights. $%$&%$#@!!!!! Now I can't even see what kind of Amps it's putting out. Guess I'll go to bed and try again another day.

Your symptom of no charge, moving the 3rd brush, finding a point that charges is a classic sign of a bad insulator behind the 3rd brush carriage bolt. It will need to come apart to replace the insulators. This the most common problem with a T generator.
You could use a separate, modern ammeter to more accurately read actual output. The in car unit was good for reference of activity. The high voltage reading is still telling me there is no battery connection(open) or possibly an internal battery problem. Keep picking @ it.

" The high voltage reading is still telling me there is no battery connection(open) or possibly an internal battery problem. Keep picking @ it." /// ....................//// The voltage will run high if there is a poor connection anywhere between the battery and the generator, including the entire ground path. The same is true if the battery is in poor condition. The fact that your car cranks briskly on the starter indicates that the connections between the battery and the starter are good, at least when it's cranking. However, the behavior of the generator suggests that there may be a poor connection somewhere in the charging circuit. I would think that a ground or open anywhere in the field circuit would reduce output or disable the generator entirely.