A vehicle exhibits a slow cranking condition, especially when cold. A battery load test shows the battery voltage dropping to 9.0 volts while cranking, with a current draw of 250 amps. The battery is rated at 600 CCA. What is the MOST appropriate next step in diagnosis?
- ACheck for excessive resistance in the starter circuit cables
- BCharge or replace the battery
- CPerform a parasitic draw test
- DReplace the starter motor
Show answer & explanationAnswer & explanation
Correct answer: A. Check for excessive resistance in the starter circuit cables
A healthy battery under load should maintain at least 9.6 volts during cranking. Dropping to 9.0 volts, while close, suggests the battery might be weak, but the current draw of 250 amps is significantly lower than expected for a 600 CCA battery trying to crank a cold engine (which could draw 300-400+ amps). This low current draw with a slow crank points to high resistance in the starter circuit, restricting current flow, rather than an inherently weak battery or starter.
Why the other options are wrong
- B. While 9.0V is on the lower side, the critical clue is the low current draw (250A). If the battery were the only issue, it would likely drop lower under a normal starter current draw, or the current draw would be much higher if the starter was struggling against a good battery. The low current indicates resistance is limiting the flow.
- C. A parasitic draw test is used for battery drain issues when the vehicle is off, not for slow cranking while starting.
- D. A faulty starter motor could cause slow cranking, but the low current draw (250A for a 600 CCA battery under cold conditions) suggests high resistance in the circuit, preventing the starter from drawing its full potential, rather than the starter itself being the primary issue.
Starter Circuit Resistance
Excessive electrical opposition in the path from the battery to the starter motor, limiting current flow.
- Causes slow cranking or no-crank conditions.
- Identified by voltage drop tests and current draw measurements.
- Common culprits include corroded battery terminals, loose cable connections, or damaged cables.
Memory trick: When the engine's slow to start, 'BATTERY', 'CABLES', 'STARTER' are the parts.