Electrical/Electronic Systems Flashcards

To check the continuity of wires that carry digital signals, which of the following tools can be used?

Answer: Logic probe

A logic probe is specifically designed to detect and display the presence of digital signals (high, low, or pulsing states) in electronic circuits without significantly loading the circuit. While a voltmeter can measure voltage, it is less effective for quickly interpreting the dynamic states or fast pulses characteristic of digital signals. A megger meter measures insulation resistance, and an analog meter is less precise for digital signals.

When using the passenger side control switch, the passenger side power window works properly, but when using the driver's side master control switch, the window only works in the DOWN position. Which of these possibly be the source of the problem?

Answer: An open circuit in the driver’s side master control switch

If the passenger window works correctly from its own switch but only works in the DOWN position from the driver's master control switch, it indicates an issue within the master switch itself. Specifically, the 'UP' contact or circuit for the passenger window within the driver's master switch is likely open or faulty, preventing the 'UP' signal from being sent. The passenger switch's full functionality confirms the motor and associated wiring are otherwise fine.

Which of the following statements regarding a series circuit is correct?

Answer: Highest resistance contains the highest voltage drop

In a series circuit, the current flowing through all components is the same. According to Ohm's Law (V=IR), the voltage drop across a component is directly proportional to its resistance. Therefore, the component with the highest resistance in a series circuit will experience the largest voltage drop across it.

A fully charged 12 volt battery should indicate how much voltage on the open circuit voltage (OCV) test when using a DMM (Digital Multimeter).

Answer: 12.6 volts

A fully charged 12-volt lead-acid battery consists of six individual cells, with each cell producing approximately 2.1 volts when fully charged. Therefore, a fully charged 12-volt battery should indicate around 12.6 volts (6 cells x 2.1 V/cell) when measured with a Digital Multimeter (DMM) during an open-circuit voltage (OCV) test.

Technician X says that if a fusible link in the alternator charging circuit is replaced with system sized wire, the circuit will be unprotected. Technician Y says that if a fusible link in the alternator charging circuit is replaced with system sized wire, the battery will overcharge. Who is right?

Answer: X only

A fusible link is a safety device designed to melt and open a circuit when excessive current flows, protecting other components. If a fusible link is replaced with a standard wire of the same gauge, it loses its protective function. This 'system sized wire' will not melt under overcurrent conditions, leaving the circuit unprotected and vulnerable to damage from excessive current. Technician Y's statement about overcharging is incorrect, as fusible links are for overcurrent protection, not voltage regulation.

When using a DMM voltmeter function to evaluate voltage drop, how should the meter leads be connected?

Answer: Across the circuit or component

To accurately measure voltage drop across a circuit or a specific component, the DMM voltmeter leads must be connected in parallel, or 'across,' the points where the voltage difference is to be measured. This allows the meter to read the potential difference between those two points, indicating how much voltage is being consumed or 'dropped' by that part of the circuit. Connecting in series would measure current, not voltage drop.

Two technicians are discussing a battery's state of charge. Technician X says a specific gravity of 1.225 at 80F indicates that a battery's state of charge is approximately 75%. Technician Y says you can use a hydrometer to check battery state of charge on a maintenance free battery. Who is right?

Answer: X only

Correct answer: X only Technician X is correct and Technician Y is wrong because maintenance free batteries do not have openings to check the specific gravity of the electrolyte with a hydrometer.

A starter solenoid clicks but the starter does not crank the engine. Technician X says that burned solenoid contacts could be the cause. Technician Y says that a poor battery cable connection could be the cause. Who is right?

Answer: Both X and Y

Correct answer: Both X and Y Both technicians are correct.

When linked to both sides of the rotor, an analog ohmmeter needle will not move. What does the rotor winding indicate?

Answer: It is open

Correct answer: It is open This ohmmeter is showing infinite resistance or infinity. This is what happens when the needle doesn’t move. With the rotor winding shows, the circuit is open.

When a technician performs a load test on a battery, the battery voltage falls below specifications. Which of the following actions is the MOST LIKELY to be taken?

Answer: Replace the battery

Correct answer: Replace the battery The battery was tested under load and failed.

The following could cause high starter current draw, EXCEPT:

Answer: a failed starter relay

Correct answer: a failed starter relay A failed starter relay could not be the cause of high starter current draw.

Technician X states that a short circuit to ground in a circuit decreases resistance. Technician Y states that a short circuit increases current flow. Who is correct?

Answer: Both technicians

Correct answer: Both technicians Both technicians are correct. There’s little or no resistance with a short to ground. It’s also true that the current flow increases when resistance decreases.

Two technicians are discussing testing a battery using an electronic conductance or continuity tester. Technician X says some of these testers can load test a battery. Technician Y says you need to make sure that the ignition switch and all accessories are off. Who is right?

Answer: Y only

Correct answer: Y only Technician X is wrong because this device cannot apply a load. It checks battery conductance.

On an automatic transmission vehicle, the starter does not crank and the solenoid does not click. Any of these could be the source of the problem. EXCEPT

Answer: an open solenoid hold-in winding

Correct answer: an open solenoid hold-in winding An open solenoid hold-in winding could not be the cause of the problem.

You discover the current draw is higher than specified while performing a starter current draw test. The battery voltages and cranking speed appear to be lower than the manufacturer's specifications. What's the source of your issue?

Answer: Worn bushings in the starter motor

Correct answer: Worn bushings in the starter motor As the motor turns slower, it draws more amperage. Worn bushings cause the motor to turn slower than it should. This leads to a high current draw.

Two technicians are discussing an alternator with zero output. Technician X says the field circuit may have an open circuit. Technician Y says the fusible link may be open from the battery to the alternator. Who is right?

Answer: Both X and Y

Correct answer: Both X and Y Both statements are correct.

The oil pressure light stays on whenever the engine is running. The oil pressure has been checked and is at specification. Technician X says that a ground in the circuit between the indicator light and the pressure switch could be the cause. Technician Y says that an open in the pressure switch could be the cause. Who is right?

Answer: X only

Correct answer: X only Technician X is correct. A ground in the circuit between the indicator light and the pressure switch could be the cause why the oil pressure light stays on whenever the engine is running.

Technician X states that a loose serpentine alternative drive belt might lead to overcharging. Technician Y states that undersized wiring between the battery and alternator might cause undercharging. Who is correct?

Answer: Technician Y

Correct answer: Technician Y Tech X is incorrect because undercharging is the result of a slipping belt. Tech Y is right because the undersize wiring leads to undercharging. This is caused by higher resistance.

A low-output alternator is being full-fielded to determine the cause. Which of the following is the LEAST likely result of full-fielding the alternator?

Answer: Low battery voltage level

Correct answer: Low battery voltage level Full fielding removes the regulator from controlling field current allowing the alternator to go to full output and is unlikely to produce a low battery voltage. This action normally produces high current and voltage. P (Power) = I (Current) x E (Voltage) and is least likely to occur.

With the engine running and based in the charging system shown. What will be the digital multimeter (DMM) will display?

Answer: charging circuit voltage drop

Correct answer: charging circuit voltage drop In the charging system shown, the digital multimeter (DMM) will display the charging circuit voltage drop.