What this test is for
Establish whether the 12-volt source can support the next test. A voltage reading alone does not prove battery capacity or charging performance.
Use the procedure to narrow a cause group. The result must be interpreted against the exact vehicle, equipment, and conditions.
- 01PurposeEstablish whether the 12-volt source can support the next test. A voltage reading alone does not prove battery capacity
- 02PrepareDigital multimeter or battery tester / Battery charger when required
- 03MeasurePreserve the condition / Inspect the connection path
- 04InterpretA charged battery after a jump is not the same evidence as a battery that held charge while parked.
- 05ContinueCharging-system test / Voltage-drop test
Follow the sequence, stop when evidence changes the path, and verify the exact vehicle information before acting.
Preserve the operating conditions, equipment setup, and result before moving to the next branch.
Tools and preparation
- Digital multimeter or battery tester
- Battery charger when required
- Eye protection
Procedure and interpretation
Preserve the condition
Record how long the vehicle sat, recent jump starts, temperature, and electrical symptoms before charging or disturbing the terminals.
The starting condition and history are documented.
A charged battery after a jump is not the same evidence as a battery that held charge while parked.
Inspect the connection path
With the vehicle off, inspect terminals, grounds, cables, and signs of heat or corrosion.
Connections are secure, clean, and undamaged.
A connection fault can create low voltage at the load even when the battery itself is serviceable.
Measure under the correct conditions
Use the battery type, tester mode, and test temperature specified by the equipment and vehicle information.
The result falls within the tester's stated condition bands.
A result outside the band supports further battery or connection testing; it does not identify a specific replacement part by itself.
Verify after charging
If the battery was low, charge it using the approved method and repeat the condition test.
The battery retains the expected state after the required rest or test procedure.
Failure to retain charge can redirect the diagnosis toward battery condition, draw, or charging evidence.
Record this test result
Save a bounded result and note to the selected vehicle. This is a personal record, not a verified diagnosis.
Choose a vehicle in My Garage or the vehicle selector first. IAR will not attach a test result to an unknown vehicle.
What to test next
Safety boundary
Battery safety
Prevent reverse polarity and short circuits. Batteries can produce explosive gas, corrosive electrolyte, and very high current.