- With ignition on and engine off, measure voltage between generator terminal B+, Black/Orange wire (Yellow/White wire on F250 Super-Duty and F350 Pickups) and ground. see scheme 1 If battery voltage is present, go to next step. If battery voltage is not present, repair Black/Orange wire or Yellow/White wire. See «WIRING DIAGRAMS»(ref-4600-S40626016452000070600000).
- Inspect generator for clean and tight connections. Repair or service connections as necessary. If connections are okay, test generator. See «AMPERAGE OUTPUT TEST»(ref-4600-S26129575762000070600000) and «VOLTAGE OUTPUT TEST»(ref-4600-S09547343692000070600000) under ON-VEHICLE TESTING.
Scheme 4
- Inspect appropriate fuses. See «CHARGING SYSTEM FUSE APPLICATION»(ref-4600-S34338846952000070600000) table. Replace as necessary. If fuses are okay, go to next step.
- Measure voltage between generator terminal "F" screw and ground. see scheme 3 If battery voltage is not present, go to next step. If battery voltage is present, go to step 4.
- Disconnect generator 3-pin and 1-pin connectors. Remove voltage regulator and brush holder. See «VOLTAGE REGULATOR»(ref-4600-S30350462772000070600000) under REMOVAL & INSTALLATION. Measure resistance between each generator slip ring and ground. (Scheme 4) If resistance is greater than 1000 ohms between both slip rings and ground, replace voltage regulator. If resistance between one or both slip rings and ground is less than 1000 ohms, replace generator. See «GENERATOR»(ref-4600-S16613135012000070600000) under REMOVAL & INSTALLATION.
- Start engine. Measure voltage between generator terminal B+ and ground. Increase engine speed while observing charge indicator light and voltmeter. If voltage is greater than 15 volts or indicator flickers, repair generator circuits "A" or "I". See «WIRING DIAGRAMS»(ref-4600-S40626016452000070600000). If voltage is 15 volts or less and indicator does not flicker, replace generator. See «GENERATOR»(ref-4600-S16613135012000070600000) under REMOVAL & INSTALLATION.