Automotive Service Excellence (ASE) A6 Electrical/Electronic SystemsStarting System Diagnosis and RepairMedium
A technician is performing a current draw test on a starter motor. With the engine cranking normally, the ammeter reads 120 amps. The vehicle is a 4-cylinder engine. What does this reading indicate?
- AExcessive current draw, indicating internal starter motor issues.
- BInsufficient current draw, suggesting high resistance in the battery cables.
- CNormal current draw for this type of engine, indicating the starter is healthy.
- DA discharged battery, causing the low current reading.
Show answer & explanationAnswer & explanation
Correct answer: C. Normal current draw for this type of engine, indicating the starter is healthy.
Normal starter current draw for a 4-cylinder engine typically ranges from 90 to 150 amps, depending on engine size, compression, and temperature. A reading of 120 amps falls within this expected range, indicating the starter motor is functioning correctly and not drawing excessive or insufficient current.
Why the other options are wrong
- A. Excessive current draw for a 4-cylinder would typically be above 150-200 amps, often indicating shorted windings or seized components.
- B. Insufficient current draw would be significantly lower than 90 amps and might indicate high resistance in the battery cables or a weak battery, but 120 amps is not insufficient.
- D. A discharged battery would likely result in either very high current draw (if trying to turn a seized starter) or very low/no current draw (if too weak to engage), but 120 amps with normal cranking is not indicative of a discharged battery.
Starter Current Draw
The amount of electrical current (amps) a starter motor consumes while cranking the engine.
- Varies by engine size, compression, and temperature.
- Typical range for 4-cyl: 90-150A; 6-cyl: 120-180A; 8-cyl: 150-250A.
- High draw indicates internal starter issues; low draw suggests resistance or weak battery.
Memory trick: Amps in the 'Zone' means the starter is 'On'!