Restrorob - Thanks for all your efforts. Step 4 of the troubleshooting procedure gives me pause. There is not enough clearance to remove the blower housing without first removing the engine from the mower.
I have done a jumper wire test putting 12v to the connector that feeds the ignition components, thus bypassing the switch and all circuits on the Scag side of the connector. The engine runs so long as I keep power on that. I think this narrows down the problem to the Scag side, and I'm going to jury rig it with a jumper to get some desperately needed mowing done. But the fix still eludes me.
The wires on the Scag side of the connector are all well-protected and there is no visible damage. I have to suspect the problem is in the Scag-side electronic module, part # 483029, which interconnects the ignition switch, safety switches, diode and relay, but really don't want to spend over $100 for a new one unless I'm sure it's bad. I have been unable to find an online service manual for the Turf Tiger. Anyone have any thoughts on how to test the electronic module?