System Test
- Check condition of fuse link, battery terminals, battery cables, connections and belt tension. Make any required corrections. Ensure battery is in good condition and is fully charged.
- Connect voltmeter to battery posts. Record voltmeter indication as base voltage. Start engine and operate at 1500 RPM with no electrical load. Read voltmeter when voltage stabilizes. If there is no voltage increase, or voltage increase is less than .5 volt over base voltage, go to step 4). If voltage increase is no greater than 2.0 volts, go to next step. If voltage increase is greater than 2.0 volts, go to step 12).
- Load alternator by switching heater/air conditioner blower motor to high speed and headlights to high beam. Increase engine speed to 2000 RPM. Voltmeter should indicate at least .5 volt higher than base voltage. If voltage increase is within specification, alternator operation is normal. If voltage increase is less than .5 volt higher than base voltage, go to next step.
- Unplug connector from voltage regulator. Measure resistance between harness connector "F" terminal and ground. If resistance is greater than 3 ohms, go to next step. If resistance is less than 3 ohms, check for grounded field wire to alternator or for shorted alternator field. See BENCH TESTING .
- Connect jumper wire between "A" and "F" terminals at harness connector. See Fig 1. Increase engine speed to 2000 RPM. If voltage increase is less than .5 volt, go to next step. If voltage increase is greater than .5 volt (vehicles with warning light), go to step 8). If voltage increase is greater than .5 volt (vehicles with ammeter), go to step 9).
- Remove jumper wire from regulator connector. Connect fused jumper wire between alternator BAT and FLD terminals. See Fig 2. Increase engine speed to 2000 RPM. If voltage increase is less than .5 volt, go to next step. If voltage increase is greater than .5 volt, repair defective "A" or "F" circuit wiring.
Courtesy of FORD MOTOR CO.
Courtesy of FORD MOTOR CO.
- Stop engine. Measure voltage at alternator BAT terminal. If voltage is equal to base voltage, service alternator. If voltage is not equal to base voltage, repair circuit between alternator and battery.
- Turn off all loads. Turn ignition off. Connect jumper between "A" and "F" terminals at voltage regulator harness. Start and idle engine. If voltage at regulator harness connector "S" terminal is not approximately 1/2 base voltage, go to step 10). If voltage is approximately 1/2 base voltage, replace voltage regulator. If voltage at "I" terminal is not approximately battery voltage, repair defective "I" circuit between indicator light and alternator.
- Turn off all loads. With ignition on, but engine not running, measure voltage at "I" terminal at regulator harness connector. If voltage is approximately battery voltage, replace voltage regulator. If voltage is not approximately battery voltage, repair defective "I" circuitry.
- With engine idling, measure voltage at voltage regulator harness connector "S" terminal. If voltage is approximately 1/2 base voltage, replace voltage regulator. If voltage is approximately zero, go to next step.
- With engine idling, measure voltage at alternator "S" terminal. If voltage is approximately 1/2 base voltage, repair wire between alternator "S" terminal and voltage regulator harness connector. If voltage is not approximately 1/2 base voltage, service alternator.
- Connect jumper wire between regulator base and alternator frame. If overvoltage condition still exists, go to next step. If overvoltage condition is eliminated, repair voltage regulator ground.
- Unplug regulator harness connector. If condition is corrected, replace regulator. If overvoltage condition is still present with regulator disconnected, repair short in wiring harness between alternator and regulator ("A" and "F" circuits).