Overrunning Alternator Pulleys - For a Perfect Run!

30 Januar 2019

The overrunning alternator pulley is a further development of the fixed belt pulley on the alternator. Thanks to its overrunning clutch, it damps the vibrations which are generated by cyclic irregularities in the crankshaft and also enables the engine speed to be reduced rapidly in the event of sudden load changes. An alternative design is the overrunning alternator decoupler which also offers a damping function.

The high quality of the ContiTech overrunning alternator pulleys guarantees perfect performance.

Design and function

An overrunning alternator pulley consists essentially of:

A) Belt pulley
B) Needle bearing
C) Pinch rollers with coupling function
D) Spring (only in case of overrunning alternator decoupler) 

As a result of the coupling function of the overrunning alternator pulley torque is transmitted only in one direction.

Thanks to its integrated spring/damper system, the overrunning alternator decoupler also decouples the multi V-belt from the alternator, thereby enabling it to damp resonance more effectively.


  • Avoidance of vibrations and slip in the whole belt drive
  • Very smooth operation and low noise generation
  • Optimal service life for belt and other belt drive components
  • Precisely matched to ContiTech multi V-belts
  • Belt and overrunning alternator pulley from one source in accustomed ContiTech OE quality


Replacement interval:

Overrunning alternator pulleys are subject to aging and wear and therefore have to be regularly checked and replaced. ContiTech recommends inspecting the operation of the overrunning alternator pulley every 60,000 km and, if in doubt, changing it every 120,000 km.


  • Store in a dry, dust-free and cool place (ideally 15-25°C)
  • Avoid contact with all liquids (oil, water etc.)


  • Faulty overrunning alternator pulleys are often the cause of noise or damage in the belt drive (e.g. tensioner)
  • ContiTech offers the Conti TOOL BOX OAP for fitting
  • Overrunning alternator pulleys can always be identified by their cover cap