The exact process for alternator pulley removal can vary from one car to another, so it is important to examine each particular vehicle before beginning. It is sometimes possible to remove an alternator pulley while the alternator itself remains installed in the vehicle, though it usually is necessary to remove the unit first. There are two main types of alternator pulleys, which are either pressed on or secured by a nut and a lock washer. To remove a pressed-on pulley, a puller set is required. The tool needed for most other alternator pulley removal is a pneumatic or electric air gun.
There are many reasons that an alternator pulley might need to be removed, though this operation is most commonly done when replacing the alternator. If the new pulley does not match the old one precisely, it could shred the belt or result in inadequate charging. Any time an alternator is replaced, the pulley on the new unit should be examined closely. The number of grooves on the new pulley should match the old one. They should also be of the same width, because a wider or thinner pulley can result in misalignment, which could either shred a belt or cause it to roll off.
It also can be necessary to remove an alternator pulley if the old one has been damaged. In this case, it might be possible to perform the alternator pulley removal without uninstalling the alternator itself, though modern engine compartments rarely provide enough space. For this time-saving procedure to work, both the removal and installation processes must first be considered. The tools necessary to install an alternator pulley sometimes take up more space than those required to remove one.
One common method of securing an alternator pulley is with a nut and lock washer. The easiest way to perform an alternator pulley removal in this case is usually with an electric or pneumatic air gun that is capable of producing a large amount of torque. The pulley will tend to turn along with the nut, so the tool that is used must have a great deal of initial torque to immediately break the nut loose. Securing the new pulley can be more difficult, because using an air gun in that application makes it difficult to judge whether sufficient tightening force has been applied. If the shaft is keyed with a hex pattern, it might be possible to secure it from turning with a hex bit so that the nut can be tightened with a regular wrench.
Other alternator pulleys are pressed on, in which case a special puller is required. The alternator pulley removal process in this case typically involves placing the specialized puller on the alternator and then turning it until the pulley comes off. This same tool can then be reversed to press on a new pulley and can often be used with power steering pulleys as well. If a regular puller is used instead of the correct tool, it typically will cause damage instead of easily removing the pulley.