ASE4 Engine Electrical Systems 1 — Questions and Answers
Question 1: A technician performs a voltage drop test across a battery cable and finds 0.8 volts with the engine cranking. This indicates:
- Normal resistance for a copper cable
- Excessive resistance in the cable causing a voltage drop concern (Correct answer)
- The battery has insufficient capacity
- The starter motor is drawing too much current
Correct answer: Excessive resistance in the cable causing a voltage drop concern
Acceptable voltage drop across a battery cable should be no more than 0.1–0.2 volts; 0.8 volts indicates significant resistance causing a power loss.
Question 2: What is the purpose of the alternator's voltage regulator?
- To convert AC current to DC current for battery charging
- To maintain charging voltage within a safe range regardless of engine speed (Correct answer)
- To limit maximum alternator output current
- To sense battery temperature for optimal charging
Correct answer: To maintain charging voltage within a safe range regardless of engine speed
The voltage regulator controls alternator field current to maintain output voltage between approximately 13.5–14.7V regardless of RPM or load.
Question 3: A battery load test shows the voltage drops to 9.2 volts under load. This result indicates:
- The battery passed and is serviceable
- The battery failed and should be replaced (Correct answer)
- The alternator is overcharging the battery
- Normal voltage drop under cranking conditions
Correct answer: The battery failed and should be replaced
A battery that drops below approximately 9.6 volts during a load test has failed and cannot supply adequate current for reliable starting.
Question 4: An alternator output test shows only 12.8 volts at 2,000 RPM with lights and accessories on. Normal is 13.5–14.7V. This indicates:
- Normal output — the battery is fully charged
- Low alternator output requiring further diagnosis (Correct answer)
- The battery is being overcharged
- A faulty battery not accepting charge
Correct answer: Low alternator output requiring further diagnosis
Alternator output should be higher than battery voltage to charge it — 12.8V under load at speed indicates insufficient alternator output.
Question 5: A starter motor cranks the engine slowly. Battery tests good. The NEXT step is to:
- Replace the starter motor immediately
- Perform a starter current draw test and voltage drop tests on starter circuits (Correct answer)
- Check the flywheel ring gear for damage
- Replace the battery cables
Correct answer: Perform a starter current draw test and voltage drop tests on starter circuits
Slow cranking with a good battery requires testing starter current draw and voltage drops to distinguish between a faulty starter and high circuit resistance.
Question 6: When checking charging system output, the technician should perform the test with:
- The engine off and key on
- The engine running at 2,000 RPM with a moderate electrical load applied (Correct answer)
- The engine at idle with no loads
- The engine at WOT for maximum alternator output
Correct answer: The engine running at 2,000 RPM with a moderate electrical load applied
Testing at 2,000 RPM with a load applied reflects real-world demand and ensures the alternator is tested under the conditions it must perform.
ASE4 Engine Electrical Systems 1
A technician performs a voltage drop test across a battery cable and finds 0.8 volts with the engine cranking.
This indicates: