[bobbader]

The "third brush" is the one most directly in view as you look down into the generator with the band off. People are often unaware about how the brush is "adjustable" when those of us use that term. I'm not casting aspersions here, but your use of the words "when it came in" may mean you are repairing this problem for someone else or you are totally new to Model A's. In any event the brush itself is not adjustable nor is there any noticeable mechanism you should be looking for (like a screw driver slot) to effect an adjustment. Instead, the bracket that the brush is mounted on has a circular ring on it that allows the entire assembly to rotate around the copper commutator on the rear of the armature. Thus, the brush also moves around the commutator and this changes the charging rate. Your goal is to move the assembly in that arc around the commutator counter clockwise to the direction of the armature (with the front of the generator being the frame of reference). To be more specific, you want to move the brush assembly "up" in a direction that will bring it closer to the engine block to lessen the charge. (Moving the brush assembly clockwise and "down" toward the ground will increase the charging rate) This is done without the car running. If you can't do this with your fingers, you should be able to move it with a wooden dowel. Once the adjustment is made, go back in, start the car, and check to see if the ammeter is showing less than 15 amps. If so, your in the right direction and the ultimate goal, for regular daytime driving, is to get the adjustment to read 6-8 amps charge at driving speed. If nothing changes with your adjustment, I'd advise further examination of the generator for other issues. (If your attempts to move the brush still leave you scratching your head, you can take the back cover off one of your spare generators to understand the brush adjusting mechanism)

Good Luck, Bob Bader