Have an AF #21085, 4-6-2 steamer with a 3 wire E-unit. The motor runs fine by itself - but I have no clue how to wire the E-unit. E-unit is a reversing pendulum with 3 wires, center wire is on all the time, activating the E-unit switches between either the right or left wire. Motor is ac powered. I need wiring diagram, etc. Do not have an AF service Manual. Any help would be appreciated.