News & Info


Substitution of Alternator Pulley Device

It appears that the worldwide electrical rebuilding industry still has not learned that cutting corners may have serious consequences and end up costing the owner more in the long run.

VW Europe has just recently issued a technical service bulletin for their dealerships regarding the substitution of solid alternator pulleys for one-way clutch pulleys. The swapping in of the cheaper solid pulley in a belt drive system that has been designed with a one-way clutch pulley or Litens® OAD™ pulley may cause the tensioner to break apart. The tensioner failing is directly related to the increased vibration levels within the belt drive system once the solid pulley is substituted. Bottom line is, you should always check to see if the alternator you are rebuilding requires a one-way clutch or a Litens® OAD™ pulley. Use only what the manufacturer has designed for the system.

The tensioner will also fail if the one-way clutch is installed but is worn out, so a functional check of the one way clutch is absolutely necessary.  A worn out one-way clutch or Litens® OAD™ pulley can seize and act just like a solid pulley. The consequences of this failure mode are high torsional vibrations in the accessory drive which will cause the tensioner to exhibit increased movement. This increased movement will cause the tensioner to have decreased service life and premature failure will eventually occur.

The picture shows the Litens® ADT 950434 (VW 038 903 315C) for 1.9L SDI and TDI (MY 1995 to 2006). The accessory drive for this application has been designed with an INA one-way clutch as the alternator pulley.  Having the one way clutch installed and working correctly ensures proper functionality of the drive. The VW P/N for the one-way clutch for the Bosch alternator is 028 903 119T and 028 903 119AC for the Valeo alternator. The tensioner shown in the picture has a broken bracket. The broken bracket is directly related to the high vibration levels in the serpentine belt drive caused by the customer either substituting a solid alternator pulley or a worn out one way clutch. One-way clutches as well as Litens® OAD™ pulleys are constantly taking the vibration abuse within the accessory drive system. These pulleys are both considered parts that wear and certainly have to be checked on a regular basis.  It is considered best to change the one way clutch, belt and tensioner all at the same time as these components are all designed to have about the same service life.