Need help with a part.  I have the first version on the Williams big boy (o-guage) made in the early 90's.  The harness that connects the tender to the engine is faulty.  It has 4 wires in the connector from the tender leading to the engine.  The reverse unit will cycle but the engine will not move unless the wires are wiggled to a specific spot.  Does anyone know where I can purchase a replacement harness.  Thank you very much for your assistance