B409

The SI generator has fault detection built into the regulator. The generator will pull circuit 225 LO if any of the following conditions occur: shorted field circuit (23), open or shorted circuit 725, drive belt breakage, and over voltage/under voltage conditions.

Circuit 225 normally has 12 volts sourced to the generator to continuously signal the regulator. A short to ground on circuit 225 causes the generator to shut down and B409 to set (engine speed must be greater than 500 RPM).
1. This checks for opens or shorts to ground on circuit 725.
2. This checks circuits 23 and 225 for the fault.

Note on Intermittents
Check circuits 725, 23 and 225 for intermittent opens or shorts to ground.