Expert: jack bahm - 4/17/2009

Question
Hello from Ontario Canada. I work in the automotive electrical repair business and enjoy doing the "old stuff" I was asked to bench test a rebuilt Model A generator. I cannot get anywhere near the maximum output which I belive I have seen listed as 20A. I may get 3A at the best 3rd brush location. If you could answer a couple of questions it may save some of my hair. 1st, CW rotation viewed form drive end? 2nd, approximately what RPM for maximum output? and 3rd,is it a valid test to lift 3rd brush clear of the armature when running at moderate speed and apply 6v to it thereby providing full voltage to the field. Are there any specs for field current at 6v? OK that was #4. Sorry for the rambling letter but I know sometimes info is better. I asked the customer if he would consider replacing it with alternator as you suggest but he preferred to keep if original-IF POSSIBLE! Thanks in advance for any info Jack

Answer
I can't help you very much.  We all run alternators.  The book says to set it for 10 amps, and for 8 amps if making long runs.  It turns CCW when viewed from the rear of car.  RPM should be only 3 or 4 hundred to get max charge.  Niot sure what to do on the 3 brushes.  Never been there before.  The book does say to just move the 3rd brush a small amount.  Run it with the cutout.  The cutouts have a history of sticking.  Make sure that is not happening.  The old generator shops usually have no problem with the old gen.  
It should charge by just spinning it.  I don't think you have to apply any voltage to get it going.  I have spun them and got good output.  Stay with it, it will work.
Good luck
jack