A simple trick to apply (to remove the regulator itself from the fault-problem) would be to connect a jumper wire to the generator FIELD terminal of the regulator...directly to GrouND, thereby bypassing the regulator. Do this with a significant electrical load on-line, such as turning ON your navigation and taxi lights (to prevent overcharging your battery, because in this condition your generator is putting out it's maximum effort continuously. Warning: If your generator ARMature wire size (the subject of this thread) is insufficient, then it could become pretty warm after a few minutes. If it blows your gen fues/CB then do not continue this test procedure.) Do not run in this "full ON" condition for more than a few mins.
If grounding the gen FieLD circuit causes the twitching to disappear the
"fault" is likely within the regulator.
Don't panic yet...I italicized the word
"fault" because ...original-style vibrating points regulators, when working perfectly, should not cause "twitching" Amp indications. But an otherwise serviceable regulator which as slightly sticking contacts or slightly mis-adjusted VR springs might occasionally be "late" in recognizing voltage requirements and may momentarily induce an over-current situation, ...which it then recognizes, and removes the excess current by interruption.
While this might be noticeable...it would not ordinarily be considered a "fault"....but only a characteristic of the type regulator when slightly worn or out of adjustment. It would not require any action whatsoever unless it drove you nuts because you fixated on it.
(The
"fix" would be to replace the regulator.)
If, by grounding the gen field circuit, the twitching continues...then the fault is more serious and may need further investigation. Generator brushes or commutator should be inspected each 100 hours and replaced when they are reduced in prescribed length, i.e. about 1/2". Brush tension should be 25-ounces. Use a cheap postal spring-scale. (Commutator condition/repairs are beyond the scope of repair in the field, But it won't hurt to see if the mica between the commutator bars are still undercut, as they should not protrude above the bars nor should they be even with those bars. The spaces between bars may become filled with brush-carbon and can be cleaned out with a sharpened end of a hacksaw blade...but again, that's
not for the average guy...it's a repair station's job !)
What DOES stand out in my mind is the possibility of generator BEARING wear. Once a generator's bearings wear beyond limits they allow the armature to "bounce" or "wobble" and that can cause the brushes to completely un-seat momentarily. Installations such as ours, where the generator is driven directly by accy-gears, are particularly worrisome with regard to bearing wear because of the vibrations that can be passed back to the engine accy-section. (This is the major reason a rubber-shock-bushing is incorporated in this installation...to prevent generator failure from causing engine gear-train failure. If your gen rubber drive-hub ever fails...it's a good idea to have the generator rebuilt/re-certified prior to returning it back to service.) It is virtually impossible to assess generator bearing condition without removing the generator...at which point one might as well replace the bearings anyway since the work to do so would then be so easy.
But you CAN at least look at the bearing-ends with a dental mirror to see if any obvious faults lie there. Look for metal-bits at the bearing-ends and discolored bearing-ways, or blistered paint indicating excess heat. If the armature can be moved radially by hand such that any movement is visible...then the bearings are definitely shot...and you should consider yourself lucky to have discovered it before they completely let-loose!
Most authorities recommend generator bench-inspections at 500 hours, but that is largely ignored by most operators. All generators should be removed at 1,000 hours and rebuilt, regardless, in my opinion, because they typically fail shortly thereafter from lack of mx.
