Volkswagen Golf/Jetta/Cabriole 1990-1999

Alternator

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TESTING





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Fig. Many VW alternators are similar to this BOSCH unit



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Fig. Remove the connections from the rear of the alternator

Voltage Test
  1. Make sure the engine is OFF , and turn the headlights on for 15-20 seconds to remove any surface charge from the battery.
  2.  
  3. Using a Digital Volt/Ohm Meter (DVOM) set to volts DC, probe across the battery terminals.
  4.  
  5. Measure the battery voltage.
  6.  
  7. Write down the voltage reading and proceed to the next test.
  8.  

No-Load Test
  1. Connect a tachometer to the engine.
  2.  


CAUTION
Ensure that the transmission is in Park and the emergency brake is set. Blocking a wheel is optional and an added safety measure.

  1. Turn off all electrical loads (radio, blower motor, wipers, etc.)
  2.  
  3. Start the engine and increase engine speed to approximately 1500 rpm.
  4.  
  5. Measure the voltage reading at the battery with the engine holding a steady 1500 rpm. Voltage should have raised at least 0.5 volts, but no more than 2.5 volts.
  6.  
  7. If the voltage does not go up more than 0.5 volts, the alternator is not charging. If the voltage goes up more than 2.5 volts, the alternator is overcharging.
  8.  


NOTE
Usually under and overcharging is caused by a defective alternator, or its related parts (regulator), and replacement will fix the problem; however, faulty wiring and other problems can cause the charging system to malfunction. Further testing, which is not covered by this guide, will reveal the exact component failure. Many automotive parts stores have alternator bench testers available for use by customers. An alternator bench test is the most definitive way to determine the condition of your alternator.

  1. If the voltage is within specifications, proceed to the next test.
  2.  

Load Test
  1. With the engine running, turn on the blower motor and the high beams ( or other electrical accessories to place a load on the charging system).
  2.  
  3. Increase and hold engine speed to 2000 rpm.
  4.  
  5. Measure the voltage reading at the battery.
  6.  
  7. The voltage should increase at least 0.5 volts from the voltage test. If the voltage does not meet specifications, the charging system is malfunctioning.
  8.  


NOTE
Usually under and overcharging is caused by a defective alternator, or its related parts (regulator), and replacement will fix the problem; however, faulty wiring and other problems can cause the charging system to malfunction. Further testing, which is not covered by this guide, will reveal the exact component failure. Many automotive parts stores have alternator bench testers available for use by customers. An alternator bench test is the most definitive way to determine the condition of your alternator.

REMOVAL & INSTALLATION





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Fig. Location of the alternator bolts on a 1994 Jetta 2.0L, 8 valve model

Before purchasing a replacement alternator, read the specification plate on the housing. The number 14V will appear to indicate maximum voltage rating. On the same line will be two more digits followed by the letter A . This is the maximum amperage output. Be sure to purchase an alternator with the same rating. The regulator can be replaced without removing the alternator.

Fox
  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the wiring from the alternator. If necessary, mark the wires with tape or other means to ensure they are connected properly upon installation.
  4.  
  5. Loosen the alternator adjustment bolt, and remove the drive belt from the alternator.
  6.  
  7. Remove the alternator adjustment bolt, followed by the pivot bolt.
  8.  
  9. Carefully lift the alternator from the bracket.
  10.  

To install:

  1. Hold the alternator in position on the mounting bracket, and install the pivot bolt.
  2.  
  3. Install (but do not tighten) the alternator adjustment bolt.
  4.  
  5. Place the alternator drive belt on the pulley.
  6.  
  7. Adjust belt tension and tighten the mounting and adjustment bolts as necessary.
  8.  
  9. Connect the wiring to the alternator. If tape was used to identify the wires, make sure it is removed once the wires are connected.
  10.  
  11. Connect the negative battery cable.
  12.  

All other vehicles


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Fig. Alternator mounting detail-2.0L engines



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Fig. Alternator belt routing-all except VR6, with power steering, no A/C



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Fig. Alternator belt mounting detail-1993-99 diesel engines



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Fig. Diesel engine belt alternator belt routing



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Fig. Alternator belt mounting detail-1994-99 VR6 engines

  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the wiring from the alternator. If necessary, mark the wires with tape or other means to ensure they are connected properly upon installation.
  4.  
  5. Loosen the belt tension, and remove the drive belt from the alternator. On VR6 (AAA) engines only, remove the belt tensioner from the cylinder head.
  6.  
  7. Remove the alternator adjustment bolt, followed by the pivot bolts.
  8.  
  9. Carefully lift the alternator from the bracket.
  10.  

To install:

  1. Hold the alternator in position on the mounting bracket, and install the pivot bolt. On later engines with automatic belt tensioners, install the upper mounting bolt.
  2.  
  3. Install (but do not tighten) the alternator adjustment bolt (earlier models only).
  4.  
  5. Place the alternator drive belt on the pulley.
  6.  
  7. Adjust belt tension and tighten the mounting and adjustment bolts as necessary.
  8.  
  9. Connect the wiring to the alternator. If tape was used to identify the wires, make sure it is removed once the wires are connected.
  10.  
  11. Connect the negative battery cable.
  12.  

 
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