I ended having to rewire mine with a 6 pin connector. To keep the wires neat, at other's suggestion, I have a piece of shrink wrap tubing over the wires, but DO NOT actually shrink apply heat and shrink the tubing. You want it to stay flexible. I think I still have the whistle and bell backwards. The idea of the extra wires was the ability to later add a cutoff switch for the smoke unit back in the tender. I never got around to it but the capability is now there.
This failure is pretty common with this engine.
