Ford Full-Size Cars 1968-1988 Repair Guide



See Figures 1 and 2

The alternator charging system consists of the alternator, voltage regulator, warning light, battery, and fuse link wire.

A failure of any component of the charging system can cause the entire system to stop functioning. Because of this, the charging system can be very difficult to troubleshoot when problems occur.

When the ignition key is turned on, current flows from the battery, through the charging system indicator light on the instrument panel, to the voltage regulator, and to the alternator. Since the alternator is not producing any current, the alternator warning light comes on. When the engine is started, the alternator begins to produce current and turns the alternator light off. As the alternator begins to generate power, the output is divided between the battery to charge the cells, and the electrical components of the vehicle A voltage regulator is wired into the alternator to prevent it from receiving too much power which could cause serious damage to electrical components in the vehicle. Conversely, if the voltage regulator does not allow the alternator to receive enough current, the battery will not be fully charged and will eventually go dead.

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Fig. Fig. 1: Charging system circuit-rear terminal type

The battery is connected to the alternator at all times, whether the ignition key is turned on or not. If the battery were shorted to ground, the alternator would also be shorted. This could damage the alternator. To prevent this, a fuse link is installed in the wiring between the battery and the alternator on all 1970 and later models. If the battery is shorted, the fuse link is melted, protecting the alternator.

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Fig. Fig. 2: Charging system circuit-side terminal type


Several precautions must be observed with alternators to avoid damaging the unit. They are as follows:

If the battery is removed for any reason, make sure that it is reconnected with the correct polarity. Reversing the battery connections may result in damage to the one-way rectifiers.
When utilizing a booster battery as a starting aid, always connect it as follows: positive to positive, and negative (booster battery) to a good ground on the engine of the car being started.
Never use a fast charger as a booster to start cars with alternating current (AC) circuits.
When charging the battery with a fast charger, always disconnect the car battery cables.
Never attempt to polarize an alternator.
Avoid long soldering times when replacing diodes or transistors. Prolonged heat is damaging to alternators.
Do not use test lamps of more than 12 volts for checking diode continuity.
Do not short across or ground any of the terminals on the alternator.
The polarity of the battery, alternator, and regulator must be matched and considered before making any electrical connections within the system.
Never separate the alternator on an open circuit. Make sure that all connections within the circuit are clean and tight.
Disconnect the battery terminals when performing any service on the electrical system. This will eliminate the possibility of accidental reversal of polarity.
Disconnect the battery ground cable if arc welding is to be done on any part of the car.


Testing of the charging system requires the use of a Sun VAT 40 (or equivalent) charging system tester. Since this is usually not readily available, it is recommended that alternator testing be performed by a reputable repair facility equipped with this equipment.


See Figures 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12

  1. Disconnect the negative battery cable.
  3. Unplug all electrical connections (mark wire locations for correct installation) from the alternator assembly.
  5. Loosen the alternator adjusting bolt(s) and remove the drive belt.
  7. Remove the alternator mounting bolts and spacer (if equipped), and remove the alternator assembly.

To install:
  1. Position the alternator assembly to the brackets and install the attaching bolts and spacer (if equipped).
  3. Fasten all electrical connections to the alternator assembly.
  5. Position the drive belt on the alternator pulley. Adjust the belt tension. Refer to the necessary service procedures in Routine Maintenance .
  7. Connect the negative battery cable.

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Fig. Fig. 3: Alternator harness connections, except 65 ampere Autolite models-1968-72 models

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Fig. Fig. 4: Alternator harness connections, 65 ampere Autolite model-1968-72 models

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Fig. Fig. 5: 1968-72 alternator harness connections-Leece Neville 65 ampere model

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Fig. Fig. 6: Motorcraft side terminal alternator-1972 and later

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Fig. Fig. 7: Motorcraft rear terminal alternator-1973 and later

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Fig. Fig. 8: After the adjusting bolt is loosened, remove the belt from the alternator

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Fig. Fig. 9: If applicable, unclip the wire harness from the back of the alternator

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Fig. Fig. 10: Loosen and remove the wires from the alternator. They should be labeled for ease of installation

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Fig. Fig. 11: Remove the adjusting bolt

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Fig. Fig. 12: Remove the lower pivot bolt, then lift the alternator out of the engine compartment