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Truck electrical circuit fundamentals Flashcards

1
Q

what is a constant power circuit

A

circuits that are connected to the battery terminal of a starter

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2
Q

type 1 circuit breaker

A

cycle OFF when breaker rating is exceeded . breakers automatically cycle back ON once overload is removed from the system

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3
Q

Type 2 circuit breaker

A

equipped with a heat producing resistor and a bimetallic strip that responds to heat by moving away from the heat source

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4
Q

where is a type 1 circuit used

A

headlights

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5
Q

What is the purpose of daytime running lights

A

enhance the visibility of the truck during the day and poor weather conditions

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6
Q

what is the purpose of the daytime running light terminal block or module .

A

lowers system voltage by 2 or 3 v so the daytime running lights are visible but will not blind other drivers . this can also be achieved through a series of terminating resistors

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7
Q

when mounting or changing clearance /marker and tail light systems

A

always refer to government regulations

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8
Q

what Is a rheostat

A

its a heat creating variable resistor .

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9
Q

what is PWM

A

it is a digital signal that turns the circuit voltage on or off

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10
Q

how is PWM DUTY cycle measured

A

as a % value of ON time vs OFF time

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11
Q

is it possible to make some electromechanical flashers operate in LED light circuits

A

yes by adding a terminating resistor . by balancing the resistance in a system by the number of turn signal lights . if you change the number of lights the resistance value must change as well

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12
Q

on some electromechanical flashers have one extra terminal that is labelled as a pilot terminal . what would this terminal be used for

A

in most cases the output from the pilot terminal illuminates a turn signal indicator light circuit

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13
Q

how are backup lights controlled

A

a transmission mounted switch or ECM . they will come on when the driver shifts the vehicle into reverse

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14
Q

in order for the cab interior light circuit to be able to turn OFF what must happen

A

all door switches must be in a closed position

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15
Q

what is a solenoid

A

an electromechanical device that turns electrical energy into linear movement

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16
Q

what is a discrete solenoid

A

it only has two positions fully open or closed

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17
Q

a door latch would use what type of solenoid

A

a discrete solenoid

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18
Q

what is a proportional solenoid

A

a solenoid that can move in an infinite number of positions

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19
Q

what is a latching solenoid

A

is a discrete solenoid that remains fixed at the end of its travel when it is deenergized

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20
Q

why is a high value resistor installed in parallel with a solenoid

A

to prevent self induced arching when a solenoid is de energized

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21
Q

what is a clamping diode

A

acts as a one way electrical current check valve

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22
Q

DC motors use magnetism and electricity to produce what

A

rotary mechanical motion

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23
Q

what component in a DC motor rotates

A

armature

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24
Q

what is the limiting force of rotational speed of a unloaded DC motor

A

CEMF counter electromotive force

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25
what is CEMF
its the voltage produced by a DC motor when it is turning
26
what are the two types of DC motors
permanent magnet DC motors and field wound DC motors
27
how can you change the direction a PM motor rotates
by changing the polarity of the magnetic field
28
where are parallel wound dc motors used
where uniform speed and low starting torque are desirable, such as fan blower motor
29
what are some methods to allow variable speed motors to rotate at various speeds
. variable electrical resistance . multiple shunt windings . pulse width modulation
30
what is important to remember when mounting voltage-reducing resisters
never mount them near any easily melted or combustible material
31
(CMVSA) stipulates that cruise control systems must have .
three methods of engine speed control disengagement
32
what is the purpose of battery isolation switches
to prevent parasitic drains while the truck is parked
33
what is important to remember when installing a battery isolation switch
install fuses in both positive and negative leads to prevent damage to wiring harness
34
how can you reduce or eliminate interference and static noise
install a series coil (filter choke) or a parallel - connected capacitor to the units power lead - a parallel - connected capacitor can also be used to reduce noise at the source
35
how do the truck positioning system warn the driver of potential collisions
a forward looking mono pulse radar sensor able to detect fixed and moving objects up to 500ft away
36
can you turn off the CWS
no . it is always active at vehicle speeds above 24 kph
37
the tire pressure control system allows the driver to do what
to match appropriate tire pressures to the road conditions and the trucks load and speed
38
what is a stepper motor
an electronic device that only moves a set amount every time it is pulsed with an electronic current
39
even though trucks are equipped with air horn systems they must also be equipped with
an electric horn
40
what are the purpose of park contacts in a windshield wiper circuit
they return the wipers to a per set rest position by supplying current to the motor after it has been turned off allowing the motor to reach the park position
41
what is the purpose of an inverter
to turn 12 v dc power into 110 v ac power . they can be configured to produce 50 to 10000 w of ac power
42
what is the purpose of audible warning devices
to alert the driver of a potential hazard or problem involving various truck operation
43
what prevents all the warning lights from illuminating when only one warning light has been triggered
isolating diodes
44
if the alternator warning indicator light illuminates where would you be able to check to confirm the problem
the R terminal of the alternator will not show a voltage when checked with the unit operating causing the relay to not energize allowing the warning light circuit to stay energized
45
what type of gauge is connected directly into the system they are measuring
direct acting gauges
46
what are a few examples of direct acting gauges
Air pressure - Oil pressure - engine temperature - Speedometer -
47
what type of gauge requires a sending units and can receive analog and digital signals
indirect acting gauge
48
what might cause a indirect gauge to give inaccurate readings
poor or corroded electrical connections
49
what are the three types of analog gauges
. balancing coil . stepper motor . air core
50
electromagnetic gauge or balancing coil will not be affected by
voltages changes
51
how does the stepper motor gauge control the direction of movement
a microprocessor to generate a pulse width modulation signal
52
what type of gauge receives information from the vehicles j1708 and j1939
a digital gauge
53
what is the simplest type of sending unit
diaphragm sending unit
54
where would you find an example of variable resistor
a fuel sending unit
55
what is the purpose of an anti - slosh unit
an electronic filter that minimizes the gauge pointer fluctuation as fuel sloshes around the fuel tank
56
what is a thermistor
a variable resistor whose resistance changes significantly with increase and decrease in temperature
57
what are two types of gauges that can determine the condition of the truck electrical system
. voltmeter and ammeter
58
what would provide the driver with the most accurate information about the condition of the truck electrical system health
ammeter
59
what are the two different methods trucks use to display amperage on a dash mounted gauge
the ammeter circuit - shunt meter
60
what is an advantage of a shunt ammeter
the cables up to the dash gauge are small gauge size and can be protected by fuses preventing dash fire
61
the speed sensor is a
small permanent magnet-style pulse generating sensor
62
what is the first step in the procedure for calibrating the speedometer
calculate the pulse per mile
63
how is a tachometer utilized
by measures and displays the speed and revolution of the truck engine in revolutions per minute
64
what is baud rate
the speed of data transfer over network
65
how is baud rate measured
in kilo bites per second
66
what is the back bone of a network
the method of connection such as wires or fiberoptic cables
67
what is a stub
is a segment of data link that branches off the back bone and connects to each node
68
what is the maximum length a stub can be
1 meter
69
what is a node
a computer or other device that has a unique address
70
what is the vehicle communication data bus
the communication network that connects to all the multiplexed components of a vehicle system
71
what is protocol
a common language for data communication between control modules
72
what is topology
the logic structure of the control modules on the data bus
73
what is multiplexing
the ability to send and receive digital signals over a pair of twisted wires at high speed
74
what networks run at a 9600 baud rate
J1587 and J1708
75
what are the two major disadvantages of J1587/J1708
if one part of the network fails the whole network will fail, the slow communication speed limits the amount of nodes that it can support to 20
76
what is the message identifier
indicates the source address of the transmitting node
77
what is the parameter identifier
indicates what data the following message corresponds
78
what is the checksum
follows the final byte of data it is one byte long and completes the message . if the checksum is zero then the message is valid
79
what color is the J1587/J1708 twisted pair cables
orange and white
80
dose the J1587/J1708 require a terminating resistor
no
81
what is the first step in troubleshooting multiplexing
determine if the system is receiving power
82
the J1939/CAN is capable of communicating at a rate of
250kb/s
83
J1939 is a twisted pair of wires that are usually colored
green and yellow
84
what are the two types of J1939 cables
shielded and unshielded
85
what is the purpose of the drain wire in a shielded J1939 wires
is to prevent internal signals from radiating out and to block outside electromagnetic interference from corrupting the signal
86
how many twists per foot is adequate to provide a clear signal
12
87
both unshielded and shielded J1939 cables must have what at each end
120 ohm resistor
88
with two 120 ohm terminating resistors connected in parallel, the total resistance of the circuit will be
60 ohms
89
a total loss of communication in a J1939 system usually indicates
voltage or hardware problem
90
a partial loss of communication in a J1939 system will usually indicate
data bus device failure
91
when measuring the voltage between the CAN high/low and the ground if you were to obtain a voltage reading lower than 2.0 v or higher than 4.0 v what might this indicate
it is possible that one or more nodes or the bus is faulty | less than 2.0 v check connectors for continuity . for a voltage higher than 4 v check for excessive system voltage
92
if a reading of 120 ohms is obtained when measuring J1939
one if the terminating resistors is removed or is open

HET4 (39 decks)

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