Mercedes Coupes/Sedans/Wagons 1974-1984 Repair Guide

Alternator

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Since 1968, all Mercedes-Benz cars imported into the United States use 12 volt alternators, sometimes in conjunction with the transistorized (electronic) ignition system.

PRECAUTIONS



Some precautions that should be taken into consideration when working on this, or any other, AC charging system are as follows:

  1. Never switch battery polarity.
  2.  
  3. When installing a battery, always connect the grounded terminal first.
  4.  
  5. Never disconnect the battery while the engine is running.
  6.  
  7. If the molded connector is disconnected from the alternator, do not ground the hot wire.
  8.  
  9. Never run the alternator with the main output cable disconnected.
  10.  
  11. Never electric weld around the car without disconnecting the alternator.
  12.  
  13. Never apply any voltage in excess of battery voltage during testing.
  14.  
  15. Never "jump" a battery for starting purposes with more than 12 volts.
  16.  

REMOVAL & INSTALLATION



See Figures 1 through 5

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Fig. Fig. 1: To remove the alternator, disengage the electrical connections ...



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Fig. Fig. 2: ... then loosen the adjusting bolt and disconnect the drive belt



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Fig. Fig. 3: Using a ratchet, socket and a back-up wrench, loosen ...



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Fig. Fig. 4: ... then remove the mounting bolt



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Fig. Fig. 5: Remove the alternator from the engine

The alternator is located on the left or right-hand side, usually down low. Because of the location, it is sometimes easier to remove the alternator from below the vehicle. The following is a general procedure for all models.

  1. Locate the alternator and disconnect and tag all wires.
  2.  
  3. Loosen the adjusting (pivot) bolt or the adjusting mechanism and swing the alternator in toward the engine.
  4.  
  5. Remove the drive belt from the alternator pulley.
  6.  
  7. The alternator can now be removed from its mounting bracket or the bracket and alternator can be removed from the engine.
  8.  
  9. Installation is the reverse of removal.
  10.  
  11. Re-tension all of the drive belts that were loosened. See General Information And Maintenance .
  12.  

BELT TENSION ADJUSTMENT



All alternator drive belts should be tensioned to the specified deflection under thumb pressure at the middle of its longest span. See General Information And Maintenance for exact drive belt adjustment procedures.

The 190D utilizes a single V-belt with automatic tensioning. No adjustment is necessary.

 
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