MTFCA Forum

26 generator was functioning in the car.
On this car I have rebuilt the drive train, so I thought it would be a good idea to go over the starter and generator.
The previous owner had gone through the generator as it has a new insulated brush plate. The field coils are not new, however they are not grounded . Checked the armature on a growler, this passed as well.
Found one for the field coil leads was bare, so I repaired it.
Assembled it and set the neutral position for the brush plate.
Bench tested it and it puts out 6.8 - 7.00 volts at 1100 rpm.
Installed in the car….. no output.
Removed the generator , bench tested , same results.
Re installed in the car, still no output??

No mention of the cutout. Did your bench tests include the cutout?
What was the output(amps) ?
How do you know it's not working on the car? Did you check with a modern ammeter @ the cutout & hot wire?
How many growler tests? You maybe checked for shorts, but what about opens?
Welcome to generator fun.

Should have mentioned that I tested the output from the terminal post, no cutout involved.

Is the drive gear loose on the shaft? Gears in mesh? Did you try moving the third brush for higher output?

I did all the tests suggested on the growler.
Did not do an amperage test on the bench,
My thinking ( maybe not correct) is if the generator is not producing any voltage , a amp test will not tell me much

New generator gear, and yes the armature is turning.

Yes tried to adjust the moveable brush

Oops,….when I was bench testing I was turning the armature counter clockwise . When it is installed in the car it rotates clockwise .
Not sure what this tells me…..should I reverse the leads from the field coils and retest?

Dave1 wrote: ↑

Wed Jan 07, 2026 7:24 pm

Oops,….when I was bench testing I was turning the armature counter clockwise . When it is installed in the car it rotates clockwise .
Not sure what this tells me…..should I reverse the leads from the field coils and retest?

Re-read the service manual generator repair.
Re-read the section on setting the null. the null setting determines the direction of rotation for setting during testing. Your bench test system should include a power source (6V?) & an ammeter between the cut out & battery source. The point is to set gen output. Thats amps.
You can also set the generator in with the in car method. I would recommend this since your bench testing method is lacking important elements.

"Bench tested it and it puts out 6.8 - 7.00 volts at 1100 rpm."

It should read MUCH higher voltage than that. T gens are constant current, not voltage. They turn clockwise when looking directly at the gear. I stopped setting null point long ago. Ron Patterson's adjustment method is much more reliable.
If you're bench testing, set the brush plate rotation for 1A charge into a 6v battery with the 3rd brush pushed all the way away from you. Then, you can set the final charge rate once the brush plate is calibrated.

Jeff

Where is Ron Patterson’s method posted?

Jeff wrote: ↑

Thu Jan 08, 2026 1:29 am

"Bench tested it and it puts out 6.8 - 7.00 volts at 1100 rpm."

It should read MUCH higher voltage than that. T gens are constant current, not voltage. They turn clockwise when looking directly at the gear. I stopped setting null point long ago. Ron Patterson's adjustment method is much more reliable.
If you're bench testing, set the brush plate rotation for 1A charge into a 6v battery with the 3rd brush pushed all the way away from you. Then, you can set the final charge rate once the brush plate is calibrated.

Jeff

I also use Ron P's method on my bench tester. Much less aggravation to get a correct null setting leading to a correctly adjusted output.
Use the same method for in car adjusting also.

Above is the method as explained by Jeff.

Buy the book and read the setup procedure, Ron wrote a lot of it.

With the generator out of the engine, I noticed if you put an ammeter in line with a + voltage to the generator terminal and touch a bare spot on the case, the amps will be the same as the generator operating in the engine.

The test is recommended in the book, but not like mine.