I'll throw out a few situations that could be your problem ..... Are your ground connections clean? Your sure the wires to the regulator are on the proper terminals. The new generators ground pularity is the same as the old one. Could there be an inline fuse blown?
My neighbor replaced his Minneapolis-Moline tractor's generator with an automobile altenator but forgot the ground was reversed.
The 3010 diesel, as well as 4010, and early 3020 - 4020 diesels used a unique 24 volt starting/charging system. Are you sure the proper 24 volt starter is being used and you have two 12 volt batteries hooked up in series? If still in origiinal form, the left battery should be positive ground and the left negative ground. If tractor was updated with circuit breaker kit, then it should have a crossover cable between left positive and right negative terminals. If you can post some photos of wiring on generator, regulator, starter, and batteries, I might be able to verify if all is connected properly.
:bash:Sorry, I overlooked the diesel bit in the original post.:mocking: There are two black wires to the regulator. One goes from the "F" post on the regulator to the "F" post on the generator. The other goes from the indicator lamp to the "GEN" post on the regulator. It is a common mistake to put the two blacks together on the same post. The "GEN" post should have a black and a white.