BMW Coupes and Sedans 1970-1988 Repair Guide

Voltage Regulator

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REMOVAL & INSTALLATION



Depending on the year of the vehicle and the model of alternator used, the voltage regulator will be either an internal type unit where it is attached to the alternator, or an external regulator, in which case it is mounted to the side of one of the fenders in the engine compartment.

External Regulator
  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the multiple connector from the bottom of the regulator.
  4.  
  5. Remove the retaining screws from the regulator.
  6.  

On some regulator installations, there are ground wires attached to the screws securing the regulator in place. When removing the screws, the ground wires will have to be tucked aside.

  1. Lift off the regulator. If you are replacing it with another unit, make sure that the color coding is the same. Regulators with yellow tape or paint contain no radio suppression circuitry, while units with white or green tape or paint contain radio suppression circuitry.
  2.  

To install:
  1. Position the regulator and install the retaining screws. If there were ground wires attached to one or more screws, do not forget to install them.
  2.  
  3. Connect the multiple connector.
  4.  
  5. Connect the negative battery cable.
  6.  

VOLTAGE ADJUSTMENT

The voltage regulators used on most BMW's are non-adjustable. This procedure applies to external voltage regulators installed on 4-cylinder models built through 1975.

Tools required include a voltmeter, an ohmmeter, a tachometer, and test equipment which will permit you to isolate the battery and alternator from the rest of the vehicle's electrical system and a load rheostat to permit loading the system a set the correct voltage amount.

  1. Install a battery post adapter on the positive post of the battery according to the manufacture specifications. Connect the voltmeter across the battery. Hook up the tachometer using instructions provided with the unit. With all electrical accessories turned OFF , and the battery post adaptor switch closed, start the engine.
  2.  
  3. Open the post adapter switch.
  4.  
  5. Adjust the engine speed to 2500 rpm, and load the system with a 1 / 4 ohm resistance. With the voltage reading stabilized, any figure between 13.5 and 14.8 volts is acceptable.
  6.  
  7. If the reading is not within this range, remove the regulator cover and adjust the armature spring tension until the voltmeter reads 14.0 volts.
  8.  
  9. Install the cover and disconnect any equipment used.
  10.  

Integral Regulator

See Figures 1, 2 and 3

On these models, the regulator and carbon brushes are an integral assembly, and the regulator cannot be adjusted.

  1. Disconnect the negative battery cable.
  2.  
  3. Access the regulator assembly from the rear of the alternator.
  4.  

On these type models, the alternator does not have to be detached to remove and install a voltage regulator.



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Fig. Fig. 1: Remove the retaining screws from the rear of the voltage regulator



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Fig. Fig. 2: Carefully lift the regulator out of the alternator



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Fig. Fig. 3: Remove the regulator from the engine compartment

  1. Remove the mounting screws, one located at either end of the unit and slide out the regulator/brush assembly.
  2.  

To install:
  1. Position the regulator/brush assembly into position and secure with the retainer screws.
  2.  

During installation, make sure the brushes are located flat on the slip rings.

  1. Connect the negative battery cable.
  2.  

 
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