A Circuit 35 (OG/LB)
WARNING: This page is about a different car, the 2005 Ford RV Cutaway, 2005 Ford Econoline, 2005 Ford E450 Super Duty, and 2005 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
The A (battery sense) circuit 35 (OG/LB) is used to sense the battery voltage. This voltage is used by the regulator to determine the generator output. This circuit is used to supply current to the generator field (rotor). The amount of current supplied to the rotor determines the generator output.