Normal Operation
WARNING: This page is about a different car, the 2006 Ford F550 Super Duty, 2006 Ford F450 Super Duty, and 2006 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The trailer tow battery charge relay coil receives voltage from the central junction box (CJB) fuse 27 (15A) through circuit 295 (LB/PK) when the ignition switch is in the RUN position. Ground for the trailer tow battery charge relay coil is supplied through circuit 57 (BK). The CJB fuse 107 (20A) supplies voltage to the trailer tow battery charge relay. When the trailer tow battery charge relay is energized, the voltage is routed to the trailer tow connector through circuit 49 (OG).