Electronics, Circuits, Protection

What is the advantage of putting a relay in a headlight circuit?

it protects the circuit

it reduces headlight failure

there is less current flow at the switch

there is more current flow at the switch

Correct! Wrong!

Which of the following symbols indicate an item that shows a normally closed switch?

A

B

C

D

Show hint

Correct! Wrong!

Which of the following symbols indicate an item that shows a resistor?

A

B

C

D

Show hint

Correct! Wrong!

Which symbols below indicate the symbol for a diode?

A

B

C

D

Show hint

Correct! Wrong!

Which of the symbols below indicate the symbol for a relay?

A

B

C

D

Show hint

Correct! Wrong!

A short can be considered to be "copper to copper" in a circuit.

True

False

Correct! Wrong!

Which of the symbols below indicate the symbol for a wire splice?

A

B

C

D

Show hint

Correct! Wrong!

Which of the symbols below indicate the symbol for a simple coil?

A

B

C

D

Show hint

Correct! Wrong!

While testing a solenoid coil, an ohmmeter reads an infinite or O.L. reading on the auto range setting. What is likely to be the problem?

Short to ground

Shorted

Grounded

Open

Correct! Wrong!

Technician A says that circuit protection devices open when the current in the circuit falls below a predetermined level. Technician B says excessive current results from a decrease in the circuit''s resistance. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

Total current in a parallel lighting circuit will divide between branches according to:

branch voltage

branch resistance

conductor size

conductor material

Correct! Wrong!

When testing a magnetic pick-up coil (opens, shorts and grounds), what should your meter be set to?

ohms

amps

volts

diode test

Correct! Wrong!

Ohmmeter readings while testing a good diode should read:

continually in both directions

infinity in both directions

infinity in one direction and a low resistance in the other

500 ohms in both directions

Correct! Wrong!

When checking the signal lights on a pick-up truck, a technician finds that the left turn signal works fine but the right side lights comes on but do not flash. A possible problem with the system might be:

faulty flasher

poor ground on one of the signal light bulbs

short in the wiring to one of the right signal lights

grounded flasher

Correct! Wrong!

To paraphase Ohm''s Law, it states that:

current increases as resistance increases

current decreases as voltage increases

current increases as resistance decreases

voltage increases as current increases

Correct! Wrong!

A technician is diagnosing a tractor trailer units lighting system. After turning on the marker light and head switches, he notices that none of the marker lights are working, only the head lights are on. The logical first place to look for the problem would be to check:

the marker light switch

the fuse in the marker light circuit

to see if there is power at the trailer light cord

the battery connections

Correct! Wrong!

A technician needs to check for voltage in an electrical circuit. Technician A says a 12-volt test light is used by attaching one lead to a known good voltage source, then probing various points along a circuit. Technician B says one lead of the test light should be grounded, and the other used to prove various points along a circuit. Who is right?

Technician A

Technician B

Both A and B

Neither A nor B

Correct! Wrong!

On a vehicle with a 12-volt system, a switched circuit feeds a pair of 50-watt auxiliary lights. What size of fuse would be required to protect the circuit and provide a 15% cushion for surges?

5 amp fuse

10 amp fuse

15 amp fuse

15 amp circuit breaker

Correct! Wrong!

When using a voltmeter to perform a voltage drop test in a circuit, the leads should be connected in what way?

To the battery terminals

From the positive battery terminal to ground

In series with the circuit being tested

In parallel with the circuit being tested

Correct! Wrong!

The blower motor in a truck is running very slowly. An ammeter shows a low current flow. This could be caused by:

high resistance in the circuit.

low resistance in the circuit.

an overcharged battery.

a shorted blower motor.

Correct! Wrong!

The taillight bulbs are inoperative and the tail light fuse burned out. A 12-volt test light is installed in place of the fuse, the test light comes on, but the taillight bulb remains out. When the connector near the bulb is disconnected, the 12-volt test light remains on. What may be the problem?

the circuit may be grounded between the fuse and the disconnected connector.

the circuit may be open between the disconnected connector and the bulb.

the test light is connected to the wrong fuse socket.

the circuit cannot be tested by placing two bulbs in series.

Correct! Wrong!

When the driver''s door of the vehicle is opened, the interior lights illuminate, but dimly. The problem is most likely to be:

the headlight switch may be faulty.

a grounding problem to the door jam switch may be the cause.

the variable resistor on the headlight switch is adjusted too low.

the light bulb is starting to fail and is growing more dim as a result.

Correct! Wrong!

When installing new bulbs into sockets, a good idea to prevent possible corrosion of the contact surfaces is by:

cleaning all the surfaces with a wire brush to provide better contact.

coating the surfaces with paint or some other sealant to keep out the air.

coating the prongs and base of a new bulb with dielectric grease.

coating the prongs and base of a new bulb with chassis grease.

Correct! Wrong!

The Western Union splice is a proper and complete repair to a wire harness providing you:

use an ohmmeter to determine if you have resistance at the connections

get enough twists on the wire

Show hint

Correct! Wrong!

A truck is having an intermittent fault with its high beam headlights, occasionally when the floor mounted dimmer switch is activated, the headlights go out. The least likely cause would be:

a faulty headlight dimmer switch.

a loose wiring harness connector.

faulty high beam filaments inside headlamps.

faulty headlight switch.

Show hint

Correct! Wrong!

A problem is encountered with the interior cab lights of a truck. When the bulb is out of the socket and the fuse is in place, everything is fine except the light does not work. Every time that a courtesy light bulb is replaced, the 15 amp fuse protecting that circuit burns out after a few seconds. What is the likely cause?

this could be caused by a short upstream (toward source voltage) from the light.

this could be caused by short downstream (toward circuit ground) from the respective light.

the interior light circuit is overloaded, and the bulb trips the fuse.

the 15 amp fuse should be replaced with a 20 amp fuse.

Correct! Wrong!

The use of Halogen headlight bulbs requires different procedures for installation and use. Which of these do not apply?

never touch the bulb inner protective glass

have a brighter, whiter beam pattern

outlast conventional sealed-beam incandescent headlights

the overall usage cost is up to 50% higher than standard bulbs

Correct! Wrong!

In the figure below, if the clearance light switch has failed, what would happen in the circuit?

relay #1 and relay #2 would not be energized

the stoplights will fail to operate

the trailer clearance lights are not affected

the truck clearance lights are not affected

Show hint

Correct! Wrong!

A single clearance light in a circuit glows dimly. A technician connects a test light to the bulb socket terminal and the test light burns at normal brightness. What is likely to be the problem?

a bad ground to frame at the light could be the cause.

high resistance in the circuit from the battery to the light could be the cause.

the test light uses less amperage and therefore, glows brighter.

the wiring from the light switch was sized too small and is creating high resistance.

Correct! Wrong!

A non-computerized vehicle''s oil pressure warning light fails to come on, even when the engine is shut down. All of the following are possible causes of the problem EXCEPT a:

defective sending unit.

grounded wire from the light to the sending unit.

high-resistance connection between the sending unit and the wiring coming from the warning lamp.

burnt-out warning lamp bulb.

Correct! Wrong!

Which of the following is NOT used when checking a circuit for continuity?

An ohmmeter

An ammeter

A voltmeter

A test lamp

Correct! Wrong!

When using a 12-volt test lamp to test for voltage, all of the following are true EXCEPT:

the test lamp may be connected to the battery ground.

the battery should first be disconnected.

the test lamp may be connected to the chassis ground.

a weatherproof connector should never be back-probed with the test light point.

Correct! Wrong!

Checks are being made to determine the cause of a battery going dead after a few days when the equipment is sitting. Which of these statements is most correct?

a parasitic current draw of 2 amps could cause the battery to discharge.

two amps is a normal draw for a vehicle with an electronic control module.

a battery night switch with high internal resistance could be the cause.

corrosion at the battery cables would cause the batteries to drain.

Correct! Wrong!

Which of these is the LEAST likely cause of a dim headlight?

corrosion on the headlight connector

slightly damaged or broken headlight assembly

alternator output low

high resistance in the wiring to the headlamp assembly

Correct! Wrong!

In the figure shown below, the backup light circuit fuse keeps blowing. Technician A uses an ohmmeter to check the circuit across the backup light fuse contacts. Technician B uses an ammeter to check the circuit across the backup light fuse contacts. Who is right?

A only

B only

Both A and B

Neither A nor B

Correct! Wrong!

A backup light circuit is grounded between the switch and the bulbs. What would be the result?

this condition will blow the backup light fuse.

the left-hand backup light may work normally while the right-hand backup light is inoperative.

a larger fuse may have to be installed.

this will result in the backup lights being dim.

Correct! Wrong!

All the dash lights on a dash panel do not work. The least likely problem would be:

the rheostat in the headlight switch could be the cause.

a wire from the switch may have lost proper contact.

the fuse to the circuit could be the cause.

the ECM may have an active code and should be scanned.

Correct! Wrong!

A truck that has a fuel dash gauge does not change regardless of the level of fuel in the tank. To determine if the problem is in the dash gauge or the sender, the technician would first:

remove the tank and the gauge sender and test it.

remove the gauge from the dash and test it

drain all the fuel from the tank and watch the dash gauge as the level falls.

find the wire at the sending unit and ground it

Correct! Wrong!

When diagnosing a problem of whether the oil pressure sender is delivering accurate readings to the oil pressure dash gauge, a technician would

check the voltage coming from the sending unit when the vehicle is running.

use an auxiliary gauge to check the oil pressure manually.

check the grounding circuit of the sender.

all of the above

Correct! Wrong!

Which of the following symbols indicate an item that will protect an electrical circuit?

A

B

C

D

Show hint

Correct! Wrong!

What is the function of the pyrometer?

Monitors fuel flow

Indicates the battery's state of charge

Indicates engine speed

Monitors temperature changes

Correct! Wrong!

When checking a mechanical water temperature gauge for an erratic reading, a correct test procedure would be:

use an ohmmeter to check the gauge''s internal resistance.

place the sensing bulb and a good thermometer in heating water.

use a voltmeter to ensure there is correct voltage to the gauge unit.

install a new gauge unit

Correct! Wrong!

It is acceptable to use an ordinary test light on:

electronic circuits and systems such as the instrument cluster.

electrical circuits such as headlamps, horns and power accessories.

sensor harness connectors.

both A and B

Correct! Wrong!

A customer says the electric horn on a truck will not stop blowing. What could be the cause?

welded diaphragm contacts inside the horn.

the horn relay may be faulty

the horn ring is the steering wheel in stuck and is always sending current to the relay

B or C could be the cause

Correct! Wrong!

The vehicle''s electric horn does not work when the horn button is depressed. To test the horn circuit, you would:

use a test lamp to check the power input to the relay

use a DMM to check the power output from the horn relay

use a test lead to ground the relay

any of the above

Correct! Wrong!

A Technician should not use a jumper wire to test:

the operation of relays

the operation of lights

the level of resistance

the operation of circuit breakers

Correct! Wrong!

An engine coolant warning light fails to come on whenever the vehicle''s key is turned on or when the vehicle is started. All of the following are possible causes EXCEPT:

a burned-out coolant warning bulb.

high resistance between the bulb and the sending unit.

grounded wire between the bulb and the sending unit.

faulty sending unit.

Correct! Wrong!

Series circuits have _______________ path for current flow:

one

more than one

a grounded

a shorted

Correct! Wrong!

Current flow is _______________ parts of a series circuit:

the same in all

not the same in all

increased in some

decreased in some

Correct! Wrong!

Each resistor in a series circuit will cause a _______________ drop across itself:

wattage

voltage

amperage

resistance

Correct! Wrong!

What is the advantage of putting a relay in a headlight circuit?

Which of the following symbols indicate an item that shows a normally closed switch?

Which of the following symbols indicate an item that shows a resistor?

Which symbols below indicate the symbol for a diode?

Which of the symbols below indicate the symbol for a relay?

A short can be considered to be "copper to copper" in a circuit.

Which of the symbols below indicate the symbol for a wire splice?

Which of the symbols below indicate the symbol for a simple coil?

While testing a solenoid coil, an ohmmeter reads an infinite or O.L. reading on the auto range setting. What is likely to be the problem?

Technician A says that circuit protection devices open when the current in the circuit falls below a predetermined level. Technician B says excessive current results from a decrease in the circuit''s resistance. Who is right?

Total current in a parallel lighting circuit will divide between branches according to:

When testing a magnetic pick-up coil (opens, shorts and grounds), what should your meter be set to?

Ohmmeter readings while testing a good diode should read:

When checking the signal lights on a pick-up truck, a technician finds that the left turn signal works fine but the right side lights comes on but do not flash. A possible problem with the system might be:

To paraphase Ohm''s Law, it states that:

A technician is diagnosing a tractor trailer units lighting system. After turning on the marker light and head switches, he notices that none of the marker lights are working, only the head lights are on. The logical first place to look for the problem would be to check:

On a vehicle with a 12-volt system, a switched circuit feeds a pair of 50-watt auxiliary lights. What size of fuse would be required to protect the circuit and provide a 15% cushion for surges?

When using a voltmeter to perform a voltage drop test in a circuit, the leads should be connected in what way?

The blower motor in a truck is running very slowly. An ammeter shows a low current flow. This could be caused by:

The taillight bulbs are inoperative and the tail light fuse burned out. A 12-volt test light is installed in place of the fuse, the test light comes on, but the taillight bulb remains out. When the connector near the bulb is disconnected, the 12-volt test light remains on. What may be the problem?

When the driver''s door of the vehicle is opened, the interior lights illuminate, but dimly. The problem is most likely to be:

When installing new bulbs into sockets, a good idea to prevent possible corrosion of the contact surfaces is by:

The Western Union splice is a proper and complete repair to a wire harness providing you:

A truck is having an intermittent fault with its high beam headlights, occasionally when the floor mounted dimmer switch is activated, the headlights go out. The least likely cause would be:

The use of Halogen headlight bulbs requires different procedures for installation and use. Which of these do not apply?

In the figure below, if the clearance light switch has failed, what would happen in the circuit?

A single clearance light in a circuit glows dimly. A technician connects a test light to the bulb socket terminal and the test light burns at normal brightness. What is likely to be the problem?

A non-computerized vehicle''s oil pressure warning light fails to come on, even when the engine is shut down. All of the following are possible causes of the problem EXCEPT a:

Which of the following is NOT used when checking a circuit for continuity?

When using a 12-volt test lamp to test for voltage, all of the following are true EXCEPT:

Checks are being made to determine the cause of a battery going dead after a few days when the equipment is sitting. Which of these statements is most correct?

Which of these is the LEAST likely cause of a dim headlight?

In the figure shown below, the backup light circuit fuse keeps blowing. Technician A uses an ohmmeter to check the circuit across the backup light fuse contacts. Technician B uses an ammeter to check the circuit across the backup light fuse contacts. Who is right?

A backup light circuit is grounded between the switch and the bulbs. What would be the result?

All the dash lights on a dash panel do not work. The least likely problem would be:

A truck that has a fuel dash gauge does not change regardless of the level of fuel in the tank. To determine if the problem is in the dash gauge or the sender, the technician would first:

When diagnosing a problem of whether the oil pressure sender is delivering accurate readings to the oil pressure dash gauge, a technician would

Which of the following symbols indicate an item that will protect an electrical circuit?

What is the function of the pyrometer?

When checking a mechanical water temperature gauge for an erratic reading, a correct test procedure would be:

It is acceptable to use an ordinary test light on:

A customer says the electric horn on a truck will not stop blowing. What could be the cause?

The vehicle''s electric horn does not work when the horn button is depressed. To test the horn circuit, you would:

A Technician should not use a jumper wire to test:

An engine coolant warning light fails to come on whenever the vehicle''s key is turned on or when the vehicle is started. All of the following are possible causes EXCEPT:

Series circuits have _______________ path for current flow:

Current flow is _______________ parts of a series circuit:

Each resistor in a series circuit will cause a _______________ drop across itself:

Success!

Heavy-Duty Mechanic - Trucks & Equipment