         
General Motors Car and Light Truck Applications If low voltage and low current output is found while testing CS alternators on the vehicle, NEVER apply battery voltage to the “L” terminal of the regulator. The alternator will begin to charge for a few seconds and then stop. The reason is that the voltage applied directly to the “L” terminal burned out the regulator. Some later CS alternators were equipped with an “all silicone voltage regulator” (ASVR). The ASVR regulator is actually a computer chip that runs on low voltages and is extremely sensitive to abnormal or high voltages. It was designed to work with various lamp bulb loads and/or computer interfaces. As a result, methods and techniques of external testing of CS alternators have changed dramatically and old habits and practices should be revised. On most late model vehicles, the power control module (PCM) controls the voltage regulator. If the PCM detects a fault in another vehicle system, it may be calibrated to shut down the alternator operation. The correct approach would be to use a scan tool to determine if the PCM has disabled the alternator operation. Locate the alternator control parameter on the scan tool data list. If the alternator command is “off” or “disabled” refer to the vehicle service guide for that vehicle. If the PCM has disabled the alternator system, check for possible faults in other non- alternator related systems or circuits. Genco installs “ASVR” type regulators manufactured by Taditel, the OE supplier to Delco Remy and Delphi in all remanufactured CS type alternators. Next month we will provide step-by-step instructions for CS alternator on-vehicle diagnostic testing. 
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