Ford Mustang/Cougar 1964-1973 Repair Guide

Voltage Regulator



See Figure 1

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Fig. Fig. 1: View of the voltage regulator location

  1. Remove the battery ground cable. On models with the regulator mounted behind the battery, it is necessary to remove the battery hold-down and to move the battery.
  3. Remove the regulator mounting screws.
  5. Disconnect the regulator from the wiring harness.

To install:
  1. Connect the new regulator to the wiring harness.
  3. Mount the regulator to the mounting plate. The radio suppression condenser mounts under one mounting screw, the ground lead under the other mounting screw. Tighten the mounting screws.
  5. If the battery was moved to gain access to the regulator, position the battery and install the hold-down. Connect the battery ground cable and test the system for proper voltage regulation.


See Figure 2

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Fig. Fig. 2: Mechanical voltage regulator adjustments

Erratic operation of the regulator, indicated by erratic movement of the voltmeter pointer during a voltage limiter test, may be caused by dirty or pitted regulator contacts. Vehicle ammeter pointer waver at certain critical engine speeds and electrical loads, is normal. Use a very fine abrasive paper such as silicon carbide, 400 grade, to clean the field relay and the voltage limiter contacts. Wear off the sharp edges of the abrasive by rubbing it against another piece of abrasive paper. Fold the abrasive paper over and pull the paper through the contacts to clean them. Keep all oil or grease from contacting the points. Do not use compressed air to clean the regulator. When adjusting the gap spacing use only hospital-clean feeler gauges.



The difference between the upper stage and lower stage regulation (0.3 V), is determined by the voltage limiter contact and core gaps. Make the gap adjustment with the regulator removed from the car. Bend the lower contact bracket to obtain a 0.017-0.022 inch gap at the lower contacts with the upper contacts closed. Maintain the contacts in alignment.

Adjust the core gap with the upper contacts closed. Loosen the center lockscrew 1 / 4 turn. Use a screwdriver blade in the adjustment slot under the lockscrew. Adjust the core gap for a 0.049-0.056 inch clearance between the armature and the core at the edge of the core closest to the contact points. Tighten the lockscrew and recheck the core gap.


Place a 0.010-0.018 inch feeler gauge on top of the coil core closest to the contact points. Hold the armature down on the gauge. Do not push down on the contact spring arm. Bend the contact post arm until the bottom contact just touches the upper contact.


Final adjustment of the regulator must be made with the regulator at normal operating temperature.

The field relay closing voltage is adjusted by bending the relay frame. To increase the closing voltage, bend the armature frame down. To decrease the closing voltage, bend the frame up.

The voltage limiter is adjusted by bending the voltage limiter spring arm. To increase the voltage setting, bend the adjusting arm downward. To decrease the voltage setting, bend the adjusting arm upward.

Before setting the voltage and before making a final voltage test, the alternator speed must be reduced to zero and the ignition switch opened momentarily, to cycle the regulator.

On some cars the location of the regulator may prevent adjustment on the car. Remove the regulator to an alternator-regulator test stand if adjustment is necessary.


Voltage Limiter

The only adjustment on the transistorized alternator regulator is the voltage limiter adjustment.

Adjustment of the transistor voltage limiter must be made with the regulator at normal operating temperature. Remove the regulator mounting screws and remove the bottom cover from the regulator. The voltage setting may be moved up or down by adjusting the 40 ohm adjustable resistor.

See Figures 3 and 4

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Fig. Fig. 3: Alternator Regulator Specifications

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Fig. Fig. 4: Alternator Regulator Specifications (cont.)