When I cranked my '21 for the first time the ammeter showed nothing on the + side. I removed the generator and found new brushes inside. I adjusted the brush holder by the manual then reinstalled the generator and adjusted the third brush. Still no charge according to the ammeter. Then yesterday with the car running there was a change in the gauge. Suddenly it shows a slight charge and when the headlights are turned on it shows 5 or 6 on the discharge side instead of the 10 that it showed before. Time to try adjusting the third brush again? Maybe there's hope.
How fast was the engine going when you did your tests. Also ... are you running with a cut out or voltage regulator?
It was sitting parked and running at a "fast idle". My cutout has a diode in it. Also I had tightened the third brush screw just to where the brush would still move then had nothing that I could tighten it with, back on the car. It's possible that it moved. I have since found a wrench that I might be able to bend.
Tommy, this Model T Generator third brush holder wrench - 5Z-806 is available from Langs and works fine!
Item Number: 5Z-806
Per Car: 1
Price: $10.50 each
tommy--go to your local parts and/or tool store and get a small 5/16 ignition end wrench and use the 12 point box end.mine is a craftsman and i used it on many a generator 3rd brush