What is the most accurate way to adjust and test the generator charging rate?

The best way to test your generator is on a generator test bench. Your local starter shop should be able to do it for you. Your 1930 should have a model 943 J generator. The specs. call for 15-18 amps at 1,700 RPM (generator speed), with 7.2 to 7.5 volts output. I always set my generators up at 12 amps instead of 15 amps. The points in the cutout should close at 650 RPM generator speed allowing the generator current to flow to the battery.

The model 943 J generator has three brushes and the third brush regulates the output. Looking at the generator, moving the third brush towards you increases the output, and moving the third brush away from you decreases the output. With the cover band off, the third brush is the one located at the very top of the generator next to the thru bolt. There is a 10-32 slotted screw on the end frame that you loosen first and then the brush will move in either direction. The correct position of the third brush is with the third brush three and a half to four comm. bars apart from the main brush. Also, the higher the RPM of the generator above the 1,700 RPM peak output, the more the amps will start to drop back from the initial setting at 1,700 RPM.



You can also set the output with the generator on the car if you have someone to watch the vehicle's amp gauge while you are adjusting the third brush.

Thank you for the information. I will set it by the second method. I bought another engine (mine has internal 's) so on the rebuild I will pull it and bench test and set.

As I have stated before. I am glad I joined the VCCA. The wealth of available technical knowledge is GREAT.