Why do some alternators have a clutch pulley?
An Overrunning Alternator Pulley (OAP) has a one-way clutch mechanism inside the hub that allows the belt to turn the alternator in one direction, but allows the alternator to free-wheel and spin at its own speed when the engine suddenly decelerates.
What’s the difference between un-clutched and clutched alternator pulleys?
A 99% test is to look at the pulley and see if there is a black, plastic cap on the end. Clutched pulleys will have a cap while un-clutched pulleys typically will not. On the alternator above the end of the pulley is covered by a black cap, thus it is a clutched-type pulley.
How do you rotate an alternator pulley in a car?
You’ll need to start by taking the serpentine belt off so that you can rotate the pulley independently of the engine. Once the belt is off, you’ll need to find a way to counter-hold the alternator internals. The easiest way is to use the cooling fins on the opposite side.
What happens when an alternator pulley goes bad?
A failed pulley will no longer clutch properly. The action of slowing down the alternator forcefully puts a lot of extra stress on the accessory/serpentine belt system.
What happens to the alternator when you shift gears?
When you shift from a lower gear to a higher gear your engine drops hundreds of RPMs in under a second. The alternator, however, is spinning at the higher speed. This would normally mean that the engine would effectively SLOW DOWN the alternator as it shifted gears and lowered RPMs.
A 99% test is to look at the pulley and see if there is a black, plastic cap on the end. Clutched pulleys will have a cap while un-clutched pulleys typically will not. On the alternator above the end of the pulley is covered by a black cap, thus it is a clutched-type pulley.
When does an overrunning alternator pulley open?
Contrary to a rigid wheel the overrunning alternator pulley opens in overhauling direction. The alternator mass and their influences are decoupled from the accessory drive. In addition, the overrunning alternator pulley decouples the alternator’s inertial torque during a significant engine speed deceleration such as changing gears.
How do you replace an alternator pulley on a car?
How to replace an alternator pulley. Replacing the alternator pulley involves counter-holding the alternator shaft while loosening the pulley securing hut. This typically requires a special alternator pulley bit set which can vary between models.
When you shift from a lower gear to a higher gear your engine drops hundreds of RPMs in under a second. The alternator, however, is spinning at the higher speed. This would normally mean that the engine would effectively SLOW DOWN the alternator as it shifted gears and lowered RPMs.