Don’t Ruin ‘Perfectly Good’ CS Generators Courtesy AC Delco Imagine this scenario: A technician is faced with a no-charge condition on a 2000 Aurora, equipped with a CS-series generator. After finding very low volt- age and current output at the generator, he feeds full battery voltage directly into the L-terminal. The generator begins to charge for a few seconds then suddenly stops. The technician concludes that the generator is bad and installs a replace- ment unit. Case closed. Or is it? Here is the plain and ugly truth: the generator was indeed ruined but not because it was defective—the techni- cian killed it. Many CS-series generators returned for warranty are “dead on arrival” as a result of the improper prac- tice of feeding battery voltage directly to the generator L-terminal. This practice typically will ruin a perfectly good CS-series generator almost instantly. Some CS generators are equipped with a new all-silicone voltage regula- tor (ASVR). The ASVR regulator is actually a computer chip. Computer components run on very low voltage and they are quite sensitive to abnor- mally high loads. The ASVR was designed to work with various lamp bulb loads or computer interfaces. As a result, methods and techniques of exter- nal testing of the CS generators have changed dramatically and are extremely important to revise old practices. Because it is important to understand proper charging system operation, always refer to the appropriate vehicle service manual when diagnosing a charging system concern. On most late model vehicle applications, the power- train control module (PCM) is in control of the voltage regulator. If the PCM detects a fault in another vehicle system, the PCM may be calibrated to shut down the generator operation. This result can, in fact, be a perfectly normal condition. The correct approach would be to use a scan tool to determine whether the PCM has disabled the generator operation. Consult service ‘BAT’ TERMINAL (B+) CARBON AMMETER This schematic diagram shows the proper connections for CS generator on-vehicle diagnostic testing. information and repair procedures for the vehicle being repaired. On-Vehicle Testing The following checklist provides a consistent, comprehensive procedure for on-vehicle CS generator testing. The procedure will prevent misdiagnosis and accidental damage to the voltage regulator or generator. All Vehicles Visual Inspection ¢ Check related wiring for poor con- nection, which may cause a short, ground or open condition. ¢ Check for a loose generator belt. ¢ Check the battery’s state of charge and open circuit voltage greater than 12.2 volts. Vehicles w/Charge Indicator Lights (Except Those with PCM or BCM Control Features) Switch ON, engine OFF, light OFF 1. With the ignition switch on, dis- connect the harness connector at the generator. 2. Attach J-41450-B CS generator tester harness to the generator and the battery per directions supplied with tester. Start the engine and run at 2,000 to 2,500 rpm. e If the generator produces more than 50 percent of the rated out- put, the generator is working as designed. Verify the battery state of charge and continue with vehi- cle circuit operation in step 3. ¢ If the generator does not produce sufficient output, replace the gen- erator per existing policy and replacement procedures and ver- ify vehicle circuit operation in step 3. ¢ Stop the engine, turn the ignition key off. 3. Vehicle circuit operation— ¢ Detach harness connector from generator. ¢ Ground the “L” terminal circuit of the harness connector with a 5-amp fused jumper lead. ¢ If light comes on, repair or replace the generator per existing policy and replacement procedures. e If light remains off, the circuit between the terminal and igni- tion switch is open—the open may be the bulb itself or other related harness connections. Engine running at 2,000 to 2,500 rpm, light ON 1. Stop the engine, turn switch to ‘run’ position.