Tools Required
ST-1201 GM P/N 12303040
Battery Side Terminal Adapters (Pair)
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 inoperative. The leakage
can be caused by tipping or overcharging the battery. |
• | Check for faulty battery terminals. |
- Do not load test a frozen battery. A frozen battery must be replaced.
Refer to
Battery Replacement
.
- Connect a voltmeter and a battery load tester to the battery terminals.
- If the battery has just
been charged or used in a vehicle:
- Apply a 300 ampere load for 15 seconds to remove surface
charge from the battery.
- Remove the load.
- Wait 15 seconds in order to let the battery recover.
- Apply the load specified on the battery label.
- After 15 seconds read the voltage.
- 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.
- If the voltage does not drop below the minimum voltage, the battery
is good and can be returned to service . Refer to
Battery Temperature Versus Voltage Drop
. Replace the battery when 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 one
of the following: |
• | 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.