Originally Posted by Mickey2

I think Singer had three pin plugs by 1930, at least on 66 and 99s. They are a bit different than the potted motor setup, but I have only seen tree the pin type. The early 99s with original knee lever controller has a bit different wire and plug than the later. I guess the wiring is much the same, but you really have to pay attention to which wire goes where to be paralell with the diagram.