I just finished replacing the brush insulators on a generator I am rebuilding (only my 2nd one). The last generator I rebuilt operated and adjusted "just like the book said". This one is a little different. Everything checked out in terms of grounds, shorts and the growler test. It motors fine with the 3rd brush down, but not with the 3rd brush up, so it can't be nulled in the test stand. The really strange part is that when I drive it, it pegs my 20 amp meter. Even when I back the 3rd brush off and rotate the whole brush assembly to get the lowest current measurement, I still get 12-15 amps. Strange, has anyone had experience with a generator that provides too much current? I have not had a chance to disassemble it yet to recheck everything. I am thinking about switching some parts with a known good generator to see if anything changes.
Ernie
Give me a call tomorrow when I am in the shop and perhaps I can help.
I am particularly interested in this passage in your message: "It motors fine with the 3rd brush down, but not with the 3rd brush up, so it can't be nulled in the test stand".
If you cannot correctly set the null point the rest of the adjustment is a waste of time.
Ron Patterson
859-881-1677 11am-4pm EST
You don't have the null setting correct. The four small screws on the back are for setting the null or neutral position. Once set and tightened, those screws should not be touched again.
The generator should NOT motor with the third brush off the commutator. You set the null position with the third brush up and tighten the four small screws on the back. After the null setting is made, then lower the third brush and the generator should motor.
Start with the third brush adjustment all the way out (away from the engine). This is the lowest setting. Report back what you get there (after setting null first).
Ops. Ron types faster.
Take him up on his offer to help.
"The generator should NOT motor with the third brush off the commutator"
If it won't motor, how is one able to set the null point?
I should have been more specific. When the null point is set correctly, the generator doesn't motor with the third brush off the comm. You rotate the brush plate until it doesn't motor or just begins to turn clockwise. But you are correct that it will motor if the null point isn't set correctly and the third brush is off the comm. It will motor in either direction by rotating the brush plate.