Test B: Warning Indicator On With Engine Running, System Is Not Charging

1. Measure voltage between ground and generator terminal B+ (Black/Orange wire) at component side. If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Black/Orange wire between generator and battery junction box. See WIRING DIAGRAMS . Retest for normal system operation.
2. Disconnect generator 3-pin harness connector. Measure voltage between ground and generator harness connector terminal "A" (Yellow/White wire). See Fig 1. If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Yellow/White wire between generator and battery junction box. See WIRING DIAGRAMS . Reconnect generator 3-pin harness connector and retest for normal system operation.
3. Start engine. Measure voltage between ground and generator harness connector terminal "I" (Light Green/Red wire). See Fig 1. If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Light Green/Red wire between generator and instrument panel. See WIRING DIAGRAMS . Retest for normal system operation.
4. Start engine. With engine running, turn on headlights and rear defogger, turn blower motor to high speed. Increase engine speed to 2000 RPM. Connect DVOM positive lead to positive battery terminal and negative lead to generator harness connector terminal B+. If voltage is less than .5 volt, replace generator. See GENERATOR  under REMOVAL & INSTALLATION. If voltage is more than .5 volt, repair open or high resistance in Black/Orange wire between generator and battery junction box. See WIRING DIAGRAMS . Retest for normal system operation.

Fig 1: Identifying Generator 3-Pin Harness Connector Terminals

Courtesy of FORD MOTOR CO.