AUT - 120 Final Exam
How many volts are present in a fully charged 12-volt battery?
12.6
What is the current in a 12-volt circuit with a 6-ohm resistor connected series?
2 amps
If the field of a 100 amp, pulse width modulated AC generator [PCM controlled] is fed a 30% duty cycle, how much current will be produced at the generator output terminal?
30 amps
When the starter spins but does NOT crank the engine, which of the following may be a cause?
a defective starter drive
Checking for excessive resistance in the starting circuit is being discussed. Technician A says connecting a voltmeter across the ground cable from the battery to the ground connection of the cable is the preferred method. Technician B says connecting an ohmmeter across the positive battery cable after it has been removed from the vehicle is the preferred method. Who is correct?
a only
Technician A disconnects the battery ground cable prior to replacing a fusible link. Technician B uses a fusible link that is larger [lower gauge number] than the circuit it protects. Who is correct?
a only
Technician A says diodes are semiconductors. Technician B says diodes function as electronic circuit relays. Who is correct?
a only
Technician A says electrical circuit resistance causes voltage drop. Technician B says high-resistance problems cause an increase in current flow. Who is correct?
a only
Technician A says transistors are semiconductors. Technician B says transistors function as one-way valves for current flow. Who is correct?
a only
If a ground circuit test reveals a voltage drop of more than 0.2 volt, the problem may be a ______.
all answers correct
Slip rings and brushes ______.
all answers correct
When depowering the high-voltage battery system of a hybrid vehicle, _____.
all answers correct
A cranking current test is performed, and the amperage is found to be less than specification. Technician A says the starter is bad and it should be replaced. Technician B insists on testing the resistance of the cables, grounds, and connections. Who is correct?
b only
Lab scopes are being discussed. Technician A says a lab scope can be used to measure resistance. Technician B says that a lab scope can be used to measure frequency by dividing the length of a cycle into 1. Who is correct?
b only
Technician A says permanent magnet starter motors are more robust than electromagnetic field type motors and can better withstand being dropped. Technician B says permanent magnet motors can produce more torque using less electric current. Who is correct?
b only
The voltage applied to the _____ of a transistor controls the flow of electric current through the transistor.
base
A vehicle is being diagnosed for a "no crank" problem. When the ignition switch is turned to the start position, a clicking [buzzing] noise is heard at the starter but the engine does not crank over. Technician A says the problem could be a weak battery. Technician B says the problem could be an open in the hold-in winding. Who is correct?
both a and b
OBDII technology is being discussed. Technician A says the OBDII system has the ability to store a freeze frame[snapshot] of the operating conditions that existed when the fault occurred. Technician B says vehicle identification must be transmitted automatically to the scan tool. Who is correct?
both a and b
Technician A checks a starter's field coils for opens by connecting an ohmmeter between the coil's power feed wire and the field coil brush lead. Technician B checks a starter's field coil for a short to ground by connecting an ohmmeter from the field coil brush lead and the starter housing. Who is correct?
both a and b
Technician A says N-type semiconductors have loose, or excess, electrons. Technician B says P-type semiconductors are positively charged materials. Who is correct?
both a and b
Technician A says a DC generator is similar in construction to an electric motor. Technician B says DC generator shave limited output, especially at low speeds. Who is correct?
both a and b
Technician A says increasing the strength of the magnetic field in an AC generator increases the voltage output. Technician B says the voltage regulator controls the strength of the rotor's magnetic field. Who is correct?
both a and b
Technician A says late model cars use maxifuses instead of fusible links. Technician B says fusible links are normally found in the engine compartment near the battery. Who is correct?
both a and b
Technician A says lead in the lead peroxide of the positive plates combines with sulfate to form lead sulfate (PbSO4)as a battery discharges. Technician B says lead sulfate forms on the negative plates as a battery discharges. Who is correct?
both a and b
Technician A says moving magnetic fields are a source of electrical energy in an automobile. Technician B says chemical reaction is a source of electrical energy in an automobile. Who is correct?
both a and b
Technician A says static electricity can generate more than 25,000 volts and can damage electronic components. Technician B says to avoid touching bare metal contacts because oils from the skin can cause corrosion and poor electrical contact. Who is correct?
both a and b
Technician A says the amount of electricity produced by an AC generator depends on the strength of the magnetic field. Technician B says it depends on the speed at which the magnetic field moves past the wires. Who is correct?
both a and b
Technician A says the charging system is needed to keep the battery fully charged and recharge the battery after starting. Technician B say the charging system supplies all the vehicle's electrical current needs after the engine starts. Who is correct?
both a and b
Technician A says the starter solenoid mounts directly on top of the starter motor. Technician B says the starter solenoid pushes the starter drive pinion into mesh with the flywheel teeth. Who is correct?
both a and b
Technician A uses a current output test to check AC generator output. Technician B uses a voltage output test to check output. Who is correct?
both a and b
The function of a resistor in an electrical circuit is to limit _____.
current (amperes)
What is the best tool to use to find the cause of an intermittent problem in a low-voltage DC circuit?
digital storage oscilloscope
The alternating current produced by the AC generator is rectified into DC (direct current) through the use of ______.
diodes
Air cooling or liquid cooling is required in an AC generator to maintain the temperature of the _____.
diodes (rectifier)
On a PCM-controlled AC generator, system voltage is controlled by varying the _____ of the current applied to the field coil.
duty cycle
Which of the following is NOT a common cause for premature battery failure?
excessive engine restarting
What is the first step when removing an old battery?
inspect and clean the area
A technician is testing a connector in a circuit with a voltmeter. With the power on in the circuit, the meter reads 12volts when the leads are placed on each side of the connector. This indicates that the connector _____
is open
_____ allows control modules to share sensor and output status information without the need for additional sensors or wiring
multiplexing
An engine cranks slowly. Technician A says a possible cause of the problem is low resistance in the starter circuit connections. Technician B says a possible cause is an open in the starter field coil circuit. Who is correct?
neither a nor b
What is the name of the formula E = I x R?
ohm's law
The device that prevents the engine from turning the armature of the starter motor is the ______.
overrunning clutch
All the following are used as circuit protection EXCEPT:
relay
When a diode is _____ current cannot flow through it.
reversed biased
A _____ is an electromagnet with a movable core that converts electrical current into mechanical movement.
solenoid
The pull-in winding and hold-in winding are part of the _____.
starter solenoid
The four basic functions of a computer are input, output, processing, and _____.
storage
When checking AC generator output using an oscilloscope, the correct pattern resembles ______.
the rounded tops of a picket fence
DMMs that can measure temperature use a _____ adapter that is placed on or near the object to be checked
thermocouple
The best way to test battery cables and terminal for excessive resistance is by _____ testing.
voltage drop
