When faced with an illuminated charge light diagnosis on most late-model vehicles, do not automatically assume the problem is inside the alternator and potentially unserviceable. The problem could be the pulley and belt drive system. Neglecting to test and diagnose the pulley can lead to unnecessary replacement.
Almost every late model car or truck is equipped with an overrunning alternator pulley (OAP) or an overrunning alternator decoupler (OAD). An OAP is a one-way clutch like a socket wrench that turns in one direction and locks when turned the other direction. An OAD operates in the same manner, but has a special clutch and spring that absorbs vibration to smooth out vibrations in the drive belt system. Regardless of the type, the pulley should be checked before condemning and removing the alternator.
These new pulleys allow the alternator to “free-wheel” or “overrun” when the belt suddenly slows down. This prevents the belt from slipping and reduces vibration. Best of all, the system need less tension and even a narrower belt can be used. This can result in a 1.5% to 2% fuel economy improvement. However, these pulleys have a limited lifespan due to how they operate internally.
OADs and OAPs behave the same, except the OAD will have a “spring feel” because of the internal spring. Testing can be performed on the vehicle with the belt attached.
Questions? Call us at 718-615-0705.
Visit us on the web at baydiagnostic.com
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