Tools Required

1. Before proper load testing, the battery must be in a fully charged state in order to obtain an accurate test. Load testing requires the use of battery side terminal adapters, GM P/N 12303040 , in order to ensure good connections.
2. Use the J 39200 , in order to measure voltage across the battery terminals. With all loads off, and the green dot showing in the hydrometer, voltage should be 12 V or higher. Unless the battery has just been discharged (such as by a load test or cranking the engine), replace the battery if the voltage is below 12 V. Refer to Battery Replacement in Engine Electrical.
3. With the J 39200 still attached, connect a battery load tester across the battery terminals.
4. If the battery has been charging, apply a 300 ampere load for 15 seconds in order to remove the surface charge from the battery. Remove the load. (Do not complete this step if the battery has not been recently charged).
5. Wait 15 seconds in order to let the battery recover. Apply the specified load located on the battery label or listed in the battery specifications table. Refer to Battery Usage .

Read the voltage after 15 seconds, then remove the load.

6. If the voltage does not drop below the minimum value, the battery is good and should be returned to service. Refer to Battery Temperature Versus Voltage Drop in Engine Electrical. The battery temperature must be estimated by feel and by the temperature the battery has been exposed to for the proceeding few hours.
7. If the voltage drops below the minimum value listed, replace the battery. Refer to Battery Replacement in Engine Electrical.