Kelly,
Boy, since I've given all my EMD technical publications to Mike Manwiller, CMO at the Heber Valley RR in Utah, I'll have to try memory.
1) Since it sounds like a main generator excitation issue, you might try checking the battery field excitation circuitry. Pay close attention to the tips on the battery field contactor.
2) Make sure that all connections are tight on the load regulator, the commutator on the LR is clean, and the brushes are good.
3) Since the problem appears intermittent, it will probably take awhile to chase the cause down, until the problem finally stays consistent.
Keep us posted.
