I am waiting for a DP3T switches to wire the Alternator. To simplify the design and provide Over Voltage Protection redundancy, I am setting up a double pole. Switch 1, will control Alternator Field voltage. Position 1 will be OFF, Position 2 (middle) will route the field to the Backup Alternatore. Position 3 (normal on position) will drive the Primary Alternator. This will assure that if the primary alternator fails, I can switch to Alt 2. And if it goes over voltage, I can switch it off (P1), then go to the middle position to energize the Backup Alt.
