Usually the voltage regulator goes sour on these. PM me and I will get you the address to a source in Pontiac Mi. that makes them. Pop off the back cover (voltage reg) and check with a multi meter your diode trio. you should get continuity one way and not the other on all three, if so, then check your brushes and field by putting your meter on each brush thus checking conductivity through the brushes contacting the slip rings and through the field windings. If good. Then congradulations on the need for a regulator. I generally just check the condition of the brushes to make sure they look good, make sure the bearings are ok and just go ahead and replace the regulator and check the diodes. Rarely are they bad.
