For 1990-2009 cars

#### Tools Required

ST-1201 GM P/N 12303040

Load testing the battery out of the vehicle requires using side terminal battery adapters on the battery to make good connections.

Before performing the battery load test inspect the battery:

• | Check for a cracked or broken case that permits loss of the electrolyte.

• | Evidence of small amounts of electrolyte leakage around the vent holes does not necessarily indicate the battery is defective. The leakage can be caused by tipping or overcharging the battery.

• | Check for faulty battery terminals.

• | Check the hydrometer. Refer to Battery Hydrometer Displays Dark or Yellow Dot .

1. Do not load test a frozen battery. A frozen battery must be replaced. Refer to Battery Replacement .
2. Connect a voltmeter and a battery load tester to the battery terminals.
3. If the battery has just been charged or used in a vehicle:
4. Apply a 300 ampere load for 15 seconds to remove surface charge from the battery.
5. Remove the load.
6. Wait 15 seconds in order to let the battery recover.
7. Apply the load specified on the battery label.
8. After 15 seconds, read the voltage then remove the load.

Important: The battery temperature must be estimated by the feel and by the temperature the battery has been exposed to for the preceding few hours.

9. The battery is good and can be returned to service If the voltage does not drop below the minimum voltage. Refer to Battery Temperature Versus Voltage Drop . Replace the battery If the voltage is less than the minimum. Refer to Battery Replacement .

### Vehicle Related Conditions

After the battery has been charged or tested and has proven to be a good battery, the cause of the no-start or slow cranking condition must be determined to prevent comebacks. If no obvious cause is evident, the vehicles electrical system should be diagnosed using the following steps:

• | If the battery has passed a load test and the engine still will not turn over or is difficult to start, check the starting system. Refer to Starting System Check .

• | If the starting system inspection reveals no abnormal conditions, but excessive cranking is required to start the vehicle, the cause must be diagnosed and corrected to reduce battery demands. Two possible causes for excessively long cranks are ignition system or fuel problems. Refer to Electronic Ignition (EI) System Diagnosis (Ignition System Check) or Hard Start in Engine Controls - 3.4L.

• | If the battery discharges while the vehicle sits for a few hours or days, the vehicle should be diagnosed for parasitic loads. Simple connection of an ammeter in series with the battery may not find the cause as the condition may not show up when power is restored unless that particular component is repeatedly cycled. Refer to Battery Electrical Drain/Parasitic Load Test .

• | If a battery becomes discharged and no excessive current drain is found, the operation of the charging system should be checked. Refer to Charging System Check .

#### Driver Related Conditions

If no cause is found for a discharged battery and the battery tests good, a light may have been left on; or the driving habits of the owner may be such that, especially with many short trips and repeated starts, the generator does not have enough time to recharge the battery between starts.