A Circuit 35 (OG/LB)
WARNING: This page is about a different car, the 2005 Ford Pickup, 2005 Ford F550 Super Duty, 2005 Ford F450 Super Duty, and 2005 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The A circuit or battery sense circuit is used to sense battery voltage. This voltage is used by the regulator to determine generator output.