Electrical and Electronic Systems Flashcards

A battery at rest shows 12.4 V open-circuit voltage. Approximately what is its state of charge?

Answer: 75%

12.6 V is about full charge and 12.4 V is roughly 75%.

When checking alternator output with a DMM on AC volts, a ripple reading above about 0.5 V AC most likely indicates:

Answer: A faulty diode in the rectifier

Excessive AC ripple means a diode is failing to rectify AC to DC properly.

With the engine running at about 2,000 rpm and all accessories off, a typical charging system voltage is:

Answer: 13.5–14.8 V

Most charging systems regulate between roughly 13.5 and 14.8 V.

The battery is fully charged and the starter solenoid clicks loudly, but the engine does not crank. What is the most likely cause?

Answer: Worn solenoid contacts or a failed starter motor

A click means the solenoid is getting a signal, so the fault is in the high-current contacts or motor.

During a battery load test at 70°F, a load equal to half the CCA rating is applied for 15 seconds. The battery passes if voltage stays above:

Answer: 9.6 V

A good battery should hold at least 9.6 V at 70°F during the load test.

Which alternator component produces the alternating current that is later rectified?

Answer: Stator

The stator windings have AC induced in them by the spinning rotor's magnetic field.

A vehicle with a manual transmission will not crank unless the clutch pedal is depressed. Which component causes this?

Answer: Clutch pedal position (start) switch

The clutch start switch opens the starter control circuit unless the pedal is pressed.