An overrunning alternator pulley enables smooth running of the multi-ribbed belt, which helps to protect the components of the front-end auxiliary drive. This also reduces noise and fuel consumption.
A defective overrunning alternator pulley causes strong vibrations in the multi-ribbed belt. This in turn results in the components of the front-end auxiliary drive being subjected to high forces and can lead to a broken belt tensioner.
The INA special tool (part no. 400 0444 10) can be used to carry out professional inspection and replacement of the overrunning alternator pulley.
Incidentally, nowadays an overrunning alternator pulley is installed in one out of every four vehicles.

OAP = Overrunning Alternator Pulley
OAD = Overrunning Alternator Decoupler

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https://aftermarket.schaeffler.com/catalog
INA OAP and OAD Overrunning Alternator Pulleys/Decouplers are available individually or in INA FEAD KITs for vehicles from
Audi, Seat, Skoda, Volkswagen, BMW, Mercedes, Ford, Opel, Hyundai, Kia, Volvo, GM, Citroen, Renault, Fiat, Alfa, etc. (Complete list in Schaeffler Aftermarket catalog)

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