AMMETER/CHARGE CIRCUIT FIX???

[Professor Fate]

My '26 will not charge
I've tried jumping the cutout while running on BAT... nuthin'!
On both BAT/MAG, no charge when I put low beam on. High beam makes ammeter show 10 charging.
Below is a pic of my switch as it is wired. Is the ammeter wired backwards?
How do I get it to charge?

[Humblej]

Dan,
You have a wiring problem, not necessarily a generator problem.
1) a cut out will only connect or disconnect the generator to the battery circuit, it will not regulate the charging. The cutout is an electromagnet that will close the circuit with the battery when the generator is producing power to allow charging, or open the circuit if the generator is not producing power so the battery does not power the generator like a motor. The amount of output from the generator is set by the 3rd brush in the generator. As per the Ford Service Manual you can adjust the generator output to match your driving habits, higher charge rate for short drives or lower charge rates for longer drives, but once set that is what the generator puts out, regardless of how much power is actually needed to run lights and charge the battery.
2) turning on the headlights will not make the generator charge the battery more, it will either charge or not depending on the cutout being open or closed. Turing on lights and seeing a charge on the ammeter indicates the ammeter is wired backwards.

Turing on the lights should cause a discharge reading on the ammeter around 8-10 A with the engine not running, and a discharge of 0-4 A with the engine running and the generator producing power and the cutout closed.

Simple test: with the engine not running, turn on the lights, does the ammeter show a charge or a discharge? It should not show a charge as lights do not produce power, they consume power. That will show you if your meter is wired backwards.

The Mag circuit will ONLY power the coils if so selected at the ignition switch. The Mag circuit is independent of the battery, generator, lights, ammeter, horn, etc. The Mag system and the battery system will never mix, comingle, or swap power. The only way to use Mag power in a starter/generator equipped Model T is power into the coils and out thru the spark plugs if Mag is selected at the ignition switch.

[Professor Fate]

Thank you!
I will go out and check shortly. This one's killing me....

Is there any chance the meter is bad? It came with the car, history unknown. If wired backwards, it's still wired per the diagram. So are the internals of the ammeter bad?

On my '23 I have to jump the cutout to get it to charge. When I do I always get sparks upon making contact on either side of the cutout. ---> This is not happening on my '26 (car in question). <---
What does this mean? The generator circuit is not grounded? Do I have paint blocking contact between the generator and the block possibly?

[Humblej]

First do the test, then we can go from there.

[MichaelPawelek]

Some reproduction ammeters for the Ford Model A look similar to some reproduction Model T ammeters and the Model A is a positive ground system. If your ammeter is working backwards it is for the Model A and the two wires on the back need to be switched.

[Professor Fate]

Gotcha! Will do. Thanks!!!

1rst ride after 2yrs of work was yesterday. Front fender brackets have been trimmed down, no longer as pictured.

[Professor Fate]

TEST RESULTS:
With battery on I put the low beam on and got a charge indicated of about 5.
With battery on I then put the high beam on and saw an indicated charge of 10.
**Car was not running during testing.


"Turing on lights and seeing a charge on the ammeter indicates the ammeter is wired backwards.

Simple test: with the engine not running, turn on the lights, does the ammeter show a charge or a discharge."

[Humblej]

Good. Now reverse the connections to the ammeter and test again, should show a discharge.

[Professor Fate]

If reversing the wires will rectify this, will it allow it to charge now?

[Humblej]

Charging is a different issue.
First, reverse the ammeter connections and test. If the ammeter is now showing a discharge with lights on, the ammeter is probably good.

Then test the cutout as follows:
With the engine off and the battery hooked up, place a test light on the rear connection of the cutout, you should get a hot connection. Then put the test light on the front side of the cutout, it should not be hot.

Start the engine and see if ammeter is showing a charge with the lights off. Test the same cutout connections with the engine running and report back.

[MichaelPawelek]

Some generators and alternators will not put out enough charge at engine idle to show up on the ammeter. When you perform the test with the engine running bump up the rpm a bit above idle.

[JTT3]

Dan just curious are you sure you have a cutout or a fun projects voltage regulator? They will look the same or similar until you turn them over to view the under side. Just in case it is a FP REGULATOR don’t flash the generator or you will toast the FP REGULATOR. Don’t ask me how I know. Below you will see what the underside of the Fun Projects Voltage Regulator looks like. If it doesn’t look like these on the underside it is probably a cutout or a diode style cut out.

[Professor Fate]

Cut outs been flashed so it's probably toast. I'll take look at it shortly.

[Scott_Conger]

Dan

cutouts do not care if they have been jumpered...modern voltage regulator does

until you take it off the generator, you will not know what has or has not happened

in any event, when removing the wire from the cutout/voltage regulator, take great care to insulate that wire end as it is hot to the battery (better yet, disconnect the battery first)...you've come too far to have to battle a blaze now.

[Professor Fate]

Here's what's on the car.

[Professor Fate]

Ammeter wires reversed. Now reading discharge on low beam (5) and high beam(10).

Cut out tested with test light. Power side at radiator side is hot with battery turned on (I have a cut off switch).
Firewall side of cut out has no power.

[Scott_Conger]

That's a diode style cut out. Now you and we know.
Assuming you measured the generator to ground, and the car was running, then you do have a malfunctioning generator. The cause for which can be myriad, so you're now into refurbishing, refreshing, or rebuilding the thing...which is not an uncommon thing.

If you don't own one, it's time to buy the MTFCA Electrical Book to see what you're getting into. The following is either advice or a prediction, depending on the path taken: any repair which involves electrical tape, and not replacement and remanufacturing of major components of the generator will lead to continuing nagging failures and the belief that generators simply are not reliable. To do one right, is not an insignificant investment in time and $$ for parts, but is worth the effort in future reliability as well as your personal understanding of how the thing works.

Finally, when you get to the point of "motoring" the thing, if it does motor, do not assume that it is functional;...meaning, all functional generators will motor, but not all generators that will motor are functional.

[TRDxB2]

Here's what's on the car.

The NU-REX Cut-out is a diode type not solenoid. So it allows current to flow in one direction.
Usually one would reference the poles of a cutout based on what they were connected to: either the battery and ammeter as indicated on the underside of the cutout. Your latest readings are what they should be. Model T ammeters are not all that accurate and your readings are within range. Now with the motor running and the headlights on you may see it showing a negative reading, this is Okay to. The generator output is good enough to charge the battery without the headlights off and the battery is good enough to run the headlights for hours on end when the ammeter shows negative so not to worry

[Humblej]

Something does not add up with your last test. Did you do the test with the trouble light at each side of the cutout with engine running or not running? With engine not running and the battery hooked up, you should have power at the battery side of the cutout and nothing at the generator side of the cutout. With the engine not running it is impossible to have power at the generator side and no power at the battery side of the cutout, if so you have solved the energy crisis and will be getting the Nobel Prize. The generator side of the cutout attaches to the post on top of the generator, the battery side attaches to the yellow wire coming from the terminal block on the firewall then to the ammeter. Call me if you want to discuss. 23 one-557-nine 972.
Jeff

[Professor Fate]

Sorry Scott.
Radiator side is the harness side from the battery. Firewall side is cutout to generator with no wire.

[speedytinc]

So with the motor running @ a range of speeds, are you getting any or varying power from the generator output terminal? That would be with the battery switch on. If not do a quick polarizing jump & check again. If still no output = dead generator.

[Professor Fate]

We're all good now. I have a correctly functioning ammeter gauge and cut out.
This was determined thru the unbelievably kind support of a board member via phone minutes ago, and all the great info/guidance here.
Only thing left is to adjust the 3rd brush a bit.

[Scott_Conger]

glad to hear...good for you

[JTT3]

This is good news so far. Adjusting the third brush can be tricky, so take your time and don’t force anything. If your generator has not been refurbished you may have an insulated gasket that is brittle, if you aren’t careful you can break it and cause the adjustable brush holder to ground to the brush frame. I loosen the nut more than is needed to move it so I can lift the 3rd brush slightly and not drag it on the insulated gasket. Others may have a different approach. Good luck & hope it works out for you.

[J1MGOLDEN]

Using that ammeter can be tricky too!

This is the original fire that caused me to rebuild that switch with the proper size large ammeter.

[J1MGOLDEN]

That fire went out when I cut the yellow wire to the battery.

That is not always the case, as about 30 years ago, I started documenting garages and barns that burned with a Model T inside.

I was up to 15 when I stopped, as the Model T was never blamed, but I saw at least 5 that the small ammeter was the blame.

Normally, one of the cardboard insulators would let the terminal post fall down and make a complete short there.

That is what happened to the left terminal in this case that started the fire.