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