the regulator senses the battery voltage and compares to the alternator voltage and "regulates" toe output to the battery... If you have a corroded wire, it will have an internal resistance which drops the voltage and makes it look like the battery is Dead / low.

I would remove the Gennie, take it to your local rebuilder, and let him run some load tests on the the unit to see if its operating correctly. If so, you probably have a wiring issue somewhere on board the Tractor. If you replaced the VR with two different other VR's (as long as they are the correct VR to work with the Gennie you have) and the same problem exsists, there's a problem somewhere. Have you load tested the Battery? If the Battery has a bad cell, that can cause the same problem. If the Battery ground cable isn't making a good connection with the chassis, that would cause the same issue. The system is searching for a ground. If the Gennie is the issue, it could be something as simple as a bent brush holder grounding inside the Gennie. Or maybe its a little more of an issue like a bad comm plate. Best thing to do is eliminate one component at a time. You'll find the problem. Or maybe the rebuilder will find the problem inside the Gennie if the problem is internal...

Steve@B&B