Magazine for the auto service professional
Issue link: http://asp.epubxp.com/i/392413
54 | September/October 2014 Alternator decouplers Servicing these vibration-reducing pulleys By Bob Weber C hevrolet dealer technical service bul- letin 99-06-04-029A stated: Condition: Some customers may comment on an intermittent accessory drive rumble noise when performing a garage shift and/or during parking lot maneuvers, such as turning the steering wheel to the lock position. This noise may also occur when turning on the air conditioning at idle conditions. Cause: Engine idle speed may drop below 600 rpm while performing a garage shift, turning the steering wheel to the lock posi- tion, or turning on the air conditioning. This noise may be amplifed by a large rate of change in engine rpm. This condition can also be aggravated by different low engine rpm driving conditions. Correction: A new generator with decou- pler pulley and reduced damping accessory drive tensioner was implemented for all Corvettes with automatic transmissions at 2001 SOP (start of production). The genera- tor with decoupler pulley was used only on Corvettes equipped with an automatic transmission. The reduced damping acces- sory drive tensioner is used on all 2001 Corvettes. That was then, this is now. Fourteen years later, we are seeing more vehicles coming from the factory with alternator overdrive decouplers (AODs). Meanwhile, millions of the decouplers have been in service, wear- ing out and showing up for replacement. Car, and many light truck, interiors have become havens from the outside world. Some argue that it has become too much so and reached the point of drivers ignoring Connections The illustration above shows the evolution of automotive charging systems. Courtesy of Litens Automotive