ASE Electrical and Electronic Systems 3 — Questions and Answers
Question 1: A fully rested battery shows an open-circuit voltage of 12.4 volts. Its approximate state of charge is:
- 100%
- 75% (Correct answer)
- 50%
- 25%
Correct answer: 75%
About 12.6 V is full charge and 12.4 V corresponds to roughly 75% state of charge.
Question 2: During a battery load test at 70°F (21°C) using half the CCA rating for 15 seconds, voltage should not fall below:
- 10.5 volts
- 11.5 volts
- 8.5 volts
- 9.6 volts (Correct answer)
Correct answer: 9.6 volts
A good battery maintains at least 9.6 V at 70°F during a 15-second half-CCA load test.
Question 3: With the battery disconnected, resistance measured between CAN High and CAN Low at DLC pins 6 and 14 on a healthy high-speed CAN bus should be about:
- 120 ohms
- 60 ohms (Correct answer)
- 240 ohms
- 0 ohms
Correct answer: 60 ohms
Two 120-ohm terminating resistors in parallel produce about 60 ohms total.
Question 4: A fuse blows instantly every time a circuit is switched on. The most likely cause is:
- An open in the circuit
- High resistance at the load
- A short to ground before the load (Correct answer)
- A corroded ground at the load
Correct answer: A short to ground before the load
A short to ground ahead of the load bypasses its resistance, causing excessive current that blows the fuse.
Question 5: A starter cranks slowly while drawing much higher than specified current. Which is the most likely cause?
- Shorted starter armature or engine mechanical binding (Correct answer)
- Open solenoid hold-in winding
- High resistance in the battery cables
- An open field coil
Correct answer: Shorted starter armature or engine mechanical binding
High current with slow cranking points to excessive load such as a shorted armature or a tight engine.
Question 6: Which starter solenoid winding is effectively de-energized once the solenoid's main contacts close?
- Hold-in winding
- Pull-in winding (Correct answer)
- Field winding
- Armature winding
Correct answer: Pull-in winding
Once the contacts close, both ends of the pull-in winding see equal voltage, so only the hold-in winding keeps the plunger engaged.
Question 7: An engine coolant temperature sensor is a negative temperature coefficient (NTC) thermistor. As coolant temperature rises, its resistance:
- Increases
- Decreases (Correct answer)
- Stays the same
- Drops to zero then returns
Correct answer: Decreases
NTC thermistors lose resistance as temperature increases.
ASE Electrical and Electronic Systems 3
A fully rested battery shows an open-circuit voltage of 12.4 volts.
Its approximate state of charge is: