GM/Detroit 6.5L – BATTERY TESTING

Tools Required:
GM P/N 12303040 (or equivalent) Battery Terminal Adapters J 39200 Digital Multimeter
The following procedure should be used for testing batteries (figure 3):

1. VISUAL INSPECTION
• Check for obvious damage, such as a cracked or broken case or cover, that could permit loss of electrolyte. If obvious damage is noted, replace the battery. Determine the cause of the damage and correct as needed. If not, proceed to step 2.
2. HYDROMETER CHECK (figure 4)
A. GREEN DOT VISIBLE – Go to step 3
B. DARK; GREEN DOT NOT VISIBLE
• Charge the battery as outlined under “Bat­tery Charging,” then proceed to step 3.

C. CLEAR OR YELLOW
• If the hydrometer is clear or light yellow, the battery is low on electrolyte and should be replaced.
3. LOAD TEST
• Load testing requires the use of battery side terminal adapters (figure 5), (GM P/N 12303040 or equivalent) to ensure good connections. Do not load test a frozen battery. Replace it.
A. Use J 39200 digital multimeter to measure volt­age across the terminals. With all loads off, and the green dot showing in the hydrometer, volt­age should be 12 volts or higher. Unless the battery has just been discharged (such as by load test or cranking the engine), replace the battery if the voltage is below 12 volts.
B. With J 39200 still attached, connect a battery load tester across the battery terminals.

C. If the battery has been charging, apply a 300 ampere load for 15 seconds to remove the sur­face charge from the battery. Remove load. (Do not complete this step if the battery has not been recently charged.)
D. Wait 15 seconds to let the battery recover.
Apply the specified load located on the battery label or listed in “Specifications.” Read the volt­age after 15 seconds, then remove the load.
E. If the voltage does not drop below the minimum value listed in figure 7, the battery is good and should be returned to service. (The battery tem­perature must be estimated by feel and by the temperature the battery has been exposed to for the proceeding few hours.)
F. If voltage drops below the minimum value list­ed, replace the battery.

 

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