HET 4 ELECTRICAL Flashcards
ELECTRICAL REVIEW AND NEW (193 cards)
1
Q
When finding electrical faults where should a tech look first?
A
Source - confirm voltage and connection
2
Q
How often should wiring be secured?
A
1.8m or 6Ft
3
Q
What size gauge of wire should be used when doing repairs?
A
OEM gauge
4
Q
What is the component called on a relay from point 85 to 86?
A
Actuator winding
5
Q
In a Parallel circuit what should total resistance be?
A
Less than the smallest resistance
6
Q
In Series circuit how can you find total resistance?
A
The sum of all resistance
7
Q
What are the two most common electrical faults?
A
Open or High Resistance
8
Q
What does MALT stand for?
A
Material
Area
Length
Temperature
9
Q
What effect can too long of wires have on a system?
A
Increase resistance
10
Q
What are the two types of grounds?
A
Chassis ground (frame)
or
Dedicated ground
11
Q
Can ALL circuits be soldered for repairs?
A
No, solder is not recommended on digital circuits
12
Q
What are some type of repairs for wiring?
A
Western union splice
crimp with Butt connector
crimp with Splice connector
solder all
13
Q
How much insulation should be removed when doing crimp style wire repairs?
A
5/16” or 7.5mm
190404b pg16
14
Q
Is series or parallel circuits the most common for lighting circuits?
A
Parallel
15
Q
Why should you let circuits warm up before testing?
A
It can affect your reading
16
Q
Operator complains that the light is not as bright as usual. The tech finds source voltage drop across the light. Is the operators complaint valid?
A
No, that is as bright as it will be with source voltage
17
Q
If you have a dim light, what could be the problem?
A
A high resistance on ground or power side
18
Q
What should be done to the system before taking resistance readings on a system?
A
De-energize the circuit or remove component
19
Q
What does a high impedance DMM have for resistance?
A
10 Mega Ohms
20
Q
Ohm’s law dictates?
A
that one volt of electrical force is required to cause one ampere of current to flow through one ohm of resistance
21
Q
In a parallel circuit what should be the voltage available through all legs of the system?
A
Source voltage (or the same)
22
Q
What is troubleshooting to find electric faults also referred to?
A
Isolating the fault (failure)
23
Q
When trying to diagnose an electrical fault, using your DMM it is okay to pierce the insulation on the wiring to find the failure?
A
No. DO NOT piece the insulation
ALWAYS connect the probes of the DMM at accessible conductor connections
24
Q
To join multi-strand wire, how much insulation should be removed. (Not a crimp style repair)
A
20mm or 3/4”
190404b pg 12
25
How are electrical schematics drawn?
De-energized and normal position
26
What is the purpose of a relay?
To use a small amount of amps to control a LARGE amount of amps
27
Why do we use relays?
To allow a smaller gauge wire
28
Do electrical schematics show exact location of components?
No
29
When repairing or connecting different gauge wires or multiple wires, what should be used?
A splice clip crimp
30
Voltage can be shown as (E), why?
Stands for Electromotive force
31
Where can high resistance be found in a wire harness that has weather pack or deutsch connectors?
At the connector, if it is corroded or not mated correctly
32
What can be used to help keep connections clean and moisture free?
O-ring seals, dielectric grease or siealant silicon can be used
33
What do manufactures publish to guide the tech through trouble shooting faults?
Flow charts
34
If a component is not working at all what is the probable fault?
Open
35
If two components work at the same time when the operator only turns ONE on what is the probable fault?
A short (shot to voltage)
36
What is the reason for headlight adjustment?
To provide max illumination or provide proper night time views without causing oncoming driver discomfort
37
What is the last step in preparing to do a headlight adjustment?
Shut down the engine, set parking brakes and chock the tires
38
What are the two movements available when adjusting headlamps?
Vertically and laterally
39
Can the headlamps be adjusted on a truck that isn't level?
No, the headlamps will have the most accurate adjustment when the vehicle is level
40
Why should the suspension be checked before aligning head lights?
A sagging suspension can create an unlevel truck
41
What are the gauge types available?
```
LED
LCD
Mechanical Analog
Electric Analog
Vacuum fluorescent information
```
42
Does cold temperatures affect Liquid Crystal Displays?
Yes
43
What are you allowed when testing specific gravity variance between highest and lowest cells specific gravity on batteries?
a) 5
b) .5
c) 0.05
d) 0.0005
0.05 (half)
44
What bias is needed to provide light from LED?
Forward bias
45
Do you need back lights in an LED gauge?
No the LED gives off the light needed
46
Does LCD gauges need a back lamp available?
Yes or you cannot read the gauge in the dark
47
What do the numbers/letters look like in a vacuum fluorescent display?
Pixels, tiny dots of light
48
Do vacuum fluorescent gauges need to be illuminated from behind?
No
49
What does multiplexing reduce?
Complexity, Cost, Weight, and Size of wiring harness
50
What are the common communication data buses?
J-1708/1587 AND J-1939
51
What do modules do with inputs and outputs?
Receive Inputs
and
Control Outputs
52
What are some circuits that for safety are on constant power?
```
Headlamps
Tail lamps
brake lights
clearance/marker lights
cab/sleeper lights
electric horn
7 PIN trailer receptacle
ignition switch
```
53
What are the two types of common circuit breaks?
Type I - auto reset (cycling)
| Type II - manual reset/repair
54
Describe the third type of circuit breaker
Type III - push button type
55
What size fusible link should be used?
4 gauge size Smaller than what it is protecting
ie. on an 8 gauge wired circuit, use a 12 gauge fusible link
56
In a light circuit with a Type I circuit breaker, what could be causing a "flashing" light?
A short to ground, allowing a higher than normal current causing the circuit breaker to open
57
How many volts are lowered with the terminal block in the daytime running light circuit?
2 or 3 volts
58
What does a terminal block need due to heat created by lowering voltage?
Aluminium heat sink
59
The daytime running light terminal block can be referred to as?
a module
60
When can Night running lights be used?
When the high beams are ON
61
What colours are clearance/marker lights?
Amber or Red depending on location
62
What is used in the dash panel lights to control the light intensity? (2 options)
Series connected rheostat
| PWM - Digital signal
63
What should a tech be caution about when mounting a rheostat in a system?
Creates heat when reducing system voltage
64
Constant power terminal can also be called?
Powered at all times terminal
65
If there is damage to the cladding sheath on a optic fibres, what is the repair?
Cannot be repaired, must be replaced
66
In a system with LEDs can electromechanical flashers be used?
No, there isn't enough current draw
67
What controls a vehicles back up lights?
Transmission-mounted switch
or
ECU
68
Describe Solenoid
An electromagnetic device - changes electrical energy into linear movement
69
What are the three categories of solenoids?
Discrete
Proportional
Latching
70
Does the return spring in a discrete solenoid hold the plunger in a relaxed position or in a fully extended position?
Relaxed
71
What are the two positions of a discrete solenoid?
Fully Retracted
or
Fully Extended
72
What could result if the sleep door is left unlatched for a long period of time? (uses a discrete solenoid)
It could overheat and melt insulation
| Making the solenoid useless
73
A proportional solenoid has how many positions?
infinite
74
If the voltage increases in a proportional solenoid what happens to the magnetic field?
Also INCREASES
75
What controls the voltage signal to a proportional solenoid?
ECU
76
What controls a latching solenoid?
Current-reversing circuit
77
Describe self-induction
Producing a voltage in the coil circuit when current flow stops
78
How can switch contact arcing be prevented?
Install a high value resistor in parallel with the solenoid coil
or
Clamping diode (self-discharge diode)
79
What does a DC motor use to produce a rotary mechanical motion?
Electricity and magnetism
80
A conductor that is bent into a U shape is also called?
An Armature
81
in a DC motor what do the stationary brushes that contact the split rings connect to?
Cables to a battery
82
A device that produces electricity from rotary mechanical motion is a?
Generator
83
The voltage that a dc motor produces is called a?
Counter Electromotive Force (CEMF)
84
If you reverse polarity in a PM motor, what will happen?
Reverse the direction of rotation
85
A shunt motor can be referred to as?
Parallel wound direct current motor
86
True or False
| A shunt motor can regulate its own speed?
TRUE
87
Where are parallel wound direct current motors used?
Fan Blower Motor
| -Where uniform speed and low starting torque are wanted
88
Field wound motors can change direction of rotation with no special features?
NO you need to add extra switches and make internal motor wiring connections
89
What must be done to a DC motor to reduce speed?
Resistors connected in series
90
If a DC motor has two shunt windings, one high resistance and one low, how many speed options can be made?
High, Medium and Low
91
If a component is on 100% of the time what is its duty cycle?
100% duty cycle
92
If a component is off 20% of the time what is its duty cycle?
80% duty cycle
93
How many ways can cruise control be shut off, as per CMVSA?
Truck Braking, Clutch Position and dash mounted switch
| in an auto trans vehicle there might only be two
94
What does a battery isolation switch help prevent?
Discharging of the battery while the truck is parked
95
What must a tech do when bypassing the battery isolation switch?
Install fuses on both the negative and positive leads to protect the wiring harness
96
What can be used to reduce or eliminate interference or static noise?
Install a series coil (filter choke) OR
| parallel-connected capacitor
97
Do permanent magnet direct current motors provide constant or variable torque?
Constant torque
98
What are the electromagnets that supply the magnetic field called?
Field Coils
99
The iron core the field coils are wound around is called?
Pole Shoes
100
How are turn signal flashers connected into the turn signal light circuit?
In Series connection
101
List the three types of Solenoids
Discrete
Proportional
Latching
102
What makes the latching solenoid very different from the other two solenoid types?
The latching solenoid does not return to its normal state by spring pressure. The magnets hold it to one position or the other
103
What does solenoid do with the electrical energy sent to it?
Make it into Linear Movement
104
How many positions are available on a discrete solenoid?
Only TWO (2)
105
True or False
| A discrete solenoid works well with long periods of operation.
False
106
How many positions does a proportional solenoid have?
Inifinite
107
What allows a proportional solenoid to be used continuously?
Fine diameter copper windings
108
True or False
| Solenoids need non-permeable cases
True
109
What is used to prevent self induction on a solenoid?
High value resistor in parallel or clamping diode (self-discharge diode)
110
What does a Direct Current motor use to produce rotary mechanical motion?
Electricity and magnetism
111
CEMF stands for?
Counter Electromotive force
112
If a field wound DC motor has too much mechanical resistance what will happen?
High Current creates high heat and can burn out circuit
113
When replacing a DC motor what should the technician be aware of?
Motor must be the correct size to give the correct speed
114
In a DC motor what is used in the circuit to avoid the generation of voltage?
Blocking diode
115
Electricity takes what path?
a) path of most resistance
b) path of least resistance
Path of least resistance
116
Why are permanent DC motors favorable?
Low Maintenance
Reliable
Constant torque
High-load application
117
A permanent magnet DC motor uses what to limit speed?
CEMF and load on the motor
118
How is rotation reversed on a PM DC motor?
Reverse polarity to the armature
119
True or False
| Parallel wound DC motors can regulate their own speed?
True
120
What are the three ways to control DC motor speed?
Variable electrical resistance
Multiple shunt windings
PWM
121
Indirect gauges can receive a signal in two ways, what are the two signal types?
Analog
OR
Digital
122
How are direct acting gauges connected to the component they are monitoring?
connected directly to source
123
What are three tyoes of analog gauges?
Balancing coil gauge
Stepper motor gauge
Air core Gauge
124
ICU stands for?
Instrument control unit
125
What is in a stepper motor gauge that allows it to generate a PWM?
Microprocessor
126
What is used to make ONE step into many MICRO steps?
a gear reduction
127
Indirectly operated electrical gauges require WHAT to transmit a signal to the dash mounted gauge?
Sending units
128
True or False
| A positive type coefficient thermistor's resistance increase as temperature increases
TRUE
129
What happens to resistance in a negative type coefficient thermistor as temperature increases?
Decreases
130
A thermistor is what kind of resistor?
Variable - to temperature
131
Anti-Slosh Module helps with what?
Minimizes the gauge pointer fluctuation as liquid moves around in tank
132
True or False
| A fuel level sending unit does not need calibration
False, may need calibration before or after install
133
What gauges can determine the condition of the trucks electrical system?
ammeter and voltmeter
134
Why are fuses used in dash circuits?
to avoid dash fires
135
A shunt ammeter uses heavy gauge cable or light gauge cables between the alternator and the battery?
Heavy gauge cable
136
With a shunt ammeter what is now possible?
cables to the dash gauge can be small gauge
137
Dash Digital ammeters use what? (2 things)
hall effect sensor
| intergrated circuit amplifier
138
When the alternator is not producing what will the gauge show?
Negative - showing the discharge
139
Speedometers indicate what?
vehicle speed in Km\h or MPH
140
What are the two speed sensor options on a transmission output shaft?
Rotating permanent magnet or Stationary permanent magnet
141
SAE stands for?
Society of automotive engineers
142
What does SAE do for electronic control systems?
Develop and set the standards
143
Backbone is also referred to as?
data bus
144
Nodes have what kind of addresses?
Unique address
145
DIP stands for?
Dual in-line package
146
What must be calculated before calibrating the speedometer?
Pulse per mile (PPM)
147
The DIP switch's purpose is what when the speedometer directly receives the speed signal from the speed sensor?
Calibrate electronic speedometers
148
PPM is found with what information?
M - tire revolutions per mile
Ra - rear axle ration
N - number of chopper teeth on tone ring
149
How many chopper teeth on a tone ring are normal?
16 or 11
150
on a J-1939-15/CAN2.0 (on highway/off road) what is the normal speed of the data link?
250 kb/s
151
If a system has a twisted pair (unshielded) what is the communication speed most likely to be?
less than 10 kb/s
152
A tachometer circuit sometimes connects to what other circuit?
Hour meter circuit
153
Baud rate can be defined as?
Speed of the data transfer over the network (kb/s)
154
What do twisted pairs of wires that are shielded prevent?
Electromagnetic interference EMI
155
Fibre optic cables can communicate at what speeds?
1 Mb/s to 10 Mb/s
156
What is the maximum length of a stub?
one metre
157
A branch is a segment of data link that branches off the back bone and connects to each ________?
Node
158
An ECM can also be considered a ______________ on the data link?
Node
159
What connects all the multiplexed components of a vehicle system?
Data bus
160
A slower, less reliable network is usually because there is no ________________?
Protocol
161
What are the two common protocols in heavy duty vehicles?
J1587 and CAN
162
CAN stands for?
Controller area network
163
CAN provides a serial communications protocol, meaning?
That all the information sent on the network is in sequence
164
True or False
| Data links only provide the transmissions of input signals between nodes and diagnostic scan tools?
FALSE
| inputs and outputs
165
Without topology are control modules created equal or gives priorities?
Without topology all modules are created EQUAL
166
Data links that have terminating resistors communicate at what baud rate?
250 Kb/s
167
A large diameter shunt winding has what kind of resistance?
Low resistance
168
A small diameter shunt winding has high resistance causing what kind of speed?
Low speed in the parallel wound DC motor
169
What does cruise control need to function?
ECM and operator input
170
How many LEDs can be burnt on a ray before the light is considered bad (failed)?
1/4 of LEDS in ray
171
Where in the message frame is the checksum?
Appears at the end of the message and is one Byte long
172
Identify the order of a SAE J1939 CAN 2.0B message frame.
Arbitration field - Control Field - Data Field - CRC Field -ACK - End of Frame
173
CRC stands for?
Circular reference check
174
ACK stands for?
Acknowledge field
175
Three consecutive recessive bits make up what in a J1939 message?
End of frame portion (terminates message)
176
Is the J1939 communicate at a faster speed or slower speed than the J1587 system?
FASTER
177
If a J1939 message is not terminated what phenomenon will result?
Standing Waves
178
Reflections can cause major problems within the communications system because?
They corrupt the signal of the messages on the data link
179
What ohms value do J1939 resistors have?
120 ohms
180
What is the DISADVANTAGE to using LED lights in colder climates than incandescent?
incandescent lamps give off heat, melting snow/ice off lamps
181
What is an advantage to using LEDs instead of incandescent lamps? (time)
LEDs turn on faster than incandescent
182
What is the purpose of the DRAIN wire on a J1939 system?
To reduce EMI, grounds to battery
183
Protocol is what in a multiplex system?
Language
184
In a system with Topology, describe priorities
Topology has all nodes as equals, priorities are sent in the message
185
How many pins does a J1587/1708 system need?
6 PIN
186
How many pins are needed on a J1939 system?
9 PIN
187
What is the best way to test a fuel sender unit?
Ohmeter - power off
188
```
True or False
The bulkhead control module can only control one other module?
```
False, can control many modules
189
What and where are _____ and ______ installed in an alternator circuit to reduce noise and interference?
In series coil (filter choke) - noise and interference
| In parallel - connected capacitor (on the power lead) - interference (voltage surges)
190
In a dash that has fibre optics supplying light to the gauges, what could cause ALL the gauges to be dark?
Source light is out
191
In a dash that has fibre optics supplying light to the gauges, what would cause one gauge to be out or dimmer than the rest?
The cladding sheath is torn
192
What is frequency of a speed sensor measured in?
Hertz
193
What is the amplitude of a speed sensor measured in?
Voltage AC
