I am trying to re-hook up the interlock on a bunton 48" walk behind. The previous owner had replaced the engine and not hooked up the kill switches to the new engine. I've located the wiring diagram and all seems fine with the interlock switches. The question I have is about the safety module. when I unscrew it from the frame, I have an non-grounded circuit. However, it will remain un-grounded no matter what I do with the interlock switches. When I screw it onto the frame, I get an open circuit if I get a clean connection between the metal braket on the module and the frame. In this case the circuit is always grounded no matter what I do. Question is about the module. Does the ground from this system come from the metal box of the module itself? If so, it seems like I might have a bad safety module. The part number for it is PL6025, which I can not find a reference too anywhere. Anyone have any idea where I might find a cross-reference for this part? The mower model is Bunton BHC-48. Thanks.