Magazine for the auto service professional
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60 | September/October 2014 several hours. Be sure to consult your labor guide before giving a quote to the customer. Corvettes and many Toyotas are among the easiest to replace. Chrysler minivans fall somewhere in the middle. However, the Dodge Caliber and its kin (Avenger, Sebring, Compass and Patriot) are among the most diffcult. The air conditioning compressor is in the way and access is from below. Experts recommend replacing the OAD at the frst indication of any noise or vibration on these vehicles. Diagnosis is fairly simple: look, listen and feel Look at the belt while the engine is running. It should not be futtering, but running smoothly throughout its circuit. Look at the belt tensioner. It should not be futtering, dithering or vibrating exces- sively. Look for signs of grease around the pulley indicating a bad seal. If you can get a view inside the alternator, the rotor should continue to spin down when you shut off the engine. If the charging system warning indicator is on, the OAD may be the culprit, not necessarily the alternator. Listen for belt rumble while the engine is running which usually indicates a problem with the OAD. With the transmission in park (neutral for manuals) and the park- ing brake applied, have an assistant rev the engine up to 2,500 to 3,000 rpm then switch off the ignition. The alternator's rotor should coast down for up to 10 sec- onds and if you hear a buzzing sound, the OAD bearing is probably shot. Using the appropriate special tools for the application, hold the pulley stationary and rotate the alternator shaft both ways while noting how it feels. The OAD should rotate smoothly in one direction with a bit of spring-back when you relax. If it will not rotate in either direction, rotates in both directions, or if there is roughness while turning, replace the OAD. Replacing the AOD There are three different ways to replace a clutch pulley and apply to both the alternator overrunning clutch (AOD) and overrunning alternator decoupler (OAD). The frst, and easiest, requires the special tools. This method is the quickest and can be done with the alternator in the vehicle in many cases. Pop the protective cap from the end of the pulley. Some can be pried off. With others, you need to pierce the cap with a pick or small screwdriver and then pry it off. Holding the pulley shaft with the proper tool, rotate the alternator' rotor shaft with a box-end wrench. Once it is free, simply spin off the pulley by hand. Spin the new pulley onto the alternator shaft then install the attachment bolt using the same special Connections Here is a cutaway view of an alternator over- running clutch (AOC) pulley. Illustration courtesy of INA This cutaway view shows an OAD pulley. Note the torsion spring (area in gold color). Illustration courtesy of Litens Automotive