On top of the maintenance-free battery is a built-in temperature compensated hydrometer. Use the hydrometer with the following diagnostic procedure.

When observing the hydrometer, make sure that the battery has a clean top. A light may be required in some poorly lighted areas.

Under normal operation, one of the following 3 indications can be observed:

Green Dot Visible (1)

Any green appearance in the hydrometer is interpreted as a green dot and the battery is ready for testing.

Dark; Green Dot Not Visible (2)

If the green dot cannot be seen, and a cranking complaint exists, proceed to Diagnosis for further testing. Also inspect the charging and electrical systems.

Clear or Light Yellow Dot (3)

A clear or light yellow dot means the fluid level is below the bottom of the hydrometer and is too low for diagnosis. This may have been caused by excessive or prolonged charging, a broken case, excessive tipping or normal battery wear out. A battery in this condition indicates high charging voltages caused by a faulty charging system. Therefore, you must inspect the charging and electrical systems. Replace the battery if a cranking complaint exists and the battery has a yellow or clear hydrometer refer to Battery Replacement .

Use the following procedure in order to test batteries:

Load Test

1. Load testing requires use of battery side terminal adapters (AC Delco part number ST-1201, GM part number 12303040 or equivalent) in order to ensure good connections. Do not load test a frozen battery. Replace the battery instead refre to Battery Replacement .
2. Use a voltmeter in order to check voltage across terminals. With all loads off, and the green dot showing in the hydrometer, voltage should be 12 volts or higher. If voltage is not 12 volts or higher, replace the battery refer to Battery Replacement .
3. With the voltmeter still attached, connect a battery load tester across the battery terminals.

Important: Do not complete the following step if the battery has not been recently charged.

4. If the battery has been on charge, apply a 300 ampere load for 15 seconds in order to remove surface charge from the battery. Remove the load.
5. Wait 15 seconds in order to let the battery recover. Apply the specified load located on the battery label. Read voltage after 15 seconds, then remove the load.

Important: Estimate the battery temperature by feel and by the temperature the battery has been exposed to for the proceeding few hours.

6. If voltage does not drop below the minimum listed, the battery is good. Return the battery to service.
7. If voltage drops below the minimum listed, replace the battery refer to Battery Replacement .