This is the Pro 12 wiring diagram:
[Linked Image]

Assuming that your wiring is unmodified (a truly heroic assumption when a pre-owned ride-on is involved), your Tecumseh's DC output (red wire) needs to connect to the mower's red wire before the upper diode - in other words, connect the red wire where you previously connected the generator output from the Briggs engine. The Tecumseh's AC output (yellow wire) needs to connect to the mower's white wire after the diode in series with the white wire. The two diodes then both pass rectified current from the AC wire to help charge the battery when the lights are off. The DC wire will only charge the battery, it will not contribute to powering the lights. I don't yet know whether your Tecumseh's green wire is dark green (kill wire, from its coil) or just green. Green wires Not Otherwise Classified from Tecumseh's are usually electrical ground wires. Ground wires need to be grounded, in this case to the mower's frame, or the body of the engine since this is a ride-on, with the engine grounded to the mower through its mountings.

Last edited by grumpy; 25/02/12 08:34 PM. Reason: Correction/clarification