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Heavy Equipment Technician Period 4 > HET 4 ELECTRICAL > Flashcards

HET 4 ELECTRICAL Flashcards

ELECTRICAL REVIEW AND NEW

1
Q

When finding electrical faults where should a tech look first?

A

Source - confirm voltage and connection

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2
Q

How often should wiring be secured?

A

1.8m or 6Ft

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3
Q

What size gauge of wire should be used when doing repairs?

A

OEM gauge

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4
Q

What is the component called on a relay from point 85 to 86?

A

Actuator winding

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5
Q

In a Parallel circuit what should total resistance be?

A

Less than the smallest resistance

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6
Q

In Series circuit how can you find total resistance?

A

The sum of all resistance

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7
Q

What are the two most common electrical faults?

A

Open or High Resistance

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8
Q

What does MALT stand for?

A

Material
Area
Length
Temperature

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9
Q

What effect can too long of wires have on a system?

A

Increase resistance

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10
Q

What are the two types of grounds?

A

Chassis ground (frame)
or
Dedicated ground

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11
Q

Can ALL circuits be soldered for repairs?

A

No, solder is not recommended on digital circuits

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12
Q

What are some type of repairs for wiring?

A

Western union splice
crimp with Butt connector
crimp with Splice connector
solder all

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13
Q

How much insulation should be removed when doing crimp style wire repairs?

A

5/16” or 7.5mm

190404b pg16

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14
Q

Is series or parallel circuits the most common for lighting circuits?

A

Parallel

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15
Q

Why should you let circuits warm up before testing?

A

It can affect your reading

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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

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17
Q

If you have a dim light, what could be the problem?

A

A high resistance on ground or power side

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18
Q

What should be done to the system before taking resistance readings on a system?

A

De-energize the circuit or remove component

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19
Q

What does a high impedance DMM have for resistance?

A

10 Mega Ohms

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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

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21
Q

In a parallel circuit what should be the voltage available through all legs of the system?

A

Source voltage (or the same)

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22
Q

What is troubleshooting to find electric faults also referred to?

A

Isolating the fault (failure)

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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

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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

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25
Q

How are electrical schematics drawn?

A

De-energized and normal position

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26
Q

What is the purpose of a relay?

A

To use a small amount of amps to control a LARGE amount of amps

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27
Q

Why do we use relays?

A

To allow a smaller gauge wire

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28
Q

Do electrical schematics show exact location of components?

A

No

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29
Q

When repairing or connecting different gauge wires or multiple wires, what should be used?

A

A splice clip crimp

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30
Q

Voltage can be shown as (E), why?

A

Stands for Electromotive force

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31
Q

Where can high resistance be found in a wire harness that has weather pack or deutsch connectors?

A

At the connector, if it is corroded or not mated correctly

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32
Q

What can be used to help keep connections clean and moisture free?

A

O-ring seals, dielectric grease or siealant silicon can be used

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33
Q

What do manufactures publish to guide the tech through trouble shooting faults?

A

Flow charts

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34
Q

If a component is not working at all what is the probable fault?

A

Open

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35
Q

If two components work at the same time when the operator only turns ONE on what is the probable fault?

A

A short (shot to voltage)

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36
Q

What is the reason for headlight adjustment?

A

To provide max illumination or provide proper night time views without causing oncoming driver discomfort

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37
Q

What is the last step in preparing to do a headlight adjustment?

A

Shut down the engine, set parking brakes and chock the tires

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38
Q

What are the two movements available when adjusting headlamps?

A

Vertically and laterally

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39
Q

Can the headlamps be adjusted on a truck that isn’t level?

A

No, the headlamps will have the most accurate adjustment when the vehicle is level

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40
Q

Why should the suspension be checked before aligning head lights?

A

A sagging suspension can create an unlevel truck

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41
Q

What are the gauge types available?

A 
LED
LCD
Mechanical Analog
Electric Analog
Vacuum fluorescent information
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42
Q

Does cold temperatures affect Liquid Crystal Displays?

A

Yes

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43
Q

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

A

0.05 (half)

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44
Q

What bias is needed to provide light from LED?

A

Forward bias

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45
Q

Do you need back lights in an LED gauge?

A

No the LED gives off the light needed

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46
Q

Does LCD gauges need a back lamp available?

A

Yes or you cannot read the gauge in the dark

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47
Q

What do the numbers/letters look like in a vacuum fluorescent display?

A

Pixels, tiny dots of light

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48
Q

Do vacuum fluorescent gauges need to be illuminated from behind?

A

No

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49
Q

What does multiplexing reduce?

A

Complexity, Cost, Weight, and Size of wiring harness

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50
Q

What are the common communication data buses?

A

J-1708/1587 AND J-1939

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51
Q

What do modules do with inputs and outputs?

A

Receive Inputs
and
Control Outputs

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52
Q

What are some circuits that for safety are on constant power?

A 
Headlamps
Tail lamps
brake lights
clearance/marker lights
cab/sleeper lights
electric horn
7 PIN trailer receptacle
ignition switch
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53
Q

What are the two types of common circuit breaks?

A

Type I - auto reset (cycling)

Type II - manual reset/repair

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54
Q

Describe the third type of circuit breaker

A

Type III - push button type

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55
Q

What size fusible link should be used?

A

4 gauge size Smaller than what it is protecting

ie. on an 8 gauge wired circuit, use a 12 gauge fusible link

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56
Q

In a light circuit with a Type I circuit breaker, what could be causing a “flashing” light?

A

A short to ground, allowing a higher than normal current causing the circuit breaker to open

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57
Q

How many volts are lowered with the terminal block in the daytime running light circuit?

A

2 or 3 volts

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58
Q

What does a terminal block need due to heat created by lowering voltage?

A

Aluminium heat sink

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59
Q

The daytime running light terminal block can be referred to as?

A

a module

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60
Q

When can Night running lights be used?

A

When the high beams are ON

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61
Q

What colours are clearance/marker lights?

A

Amber or Red depending on location

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62
Q

What is used in the dash panel lights to control the light intensity? (2 options)

A

Series connected rheostat

PWM - Digital signal

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63
Q

What should a tech be caution about when mounting a rheostat in a system?

A

Creates heat when reducing system voltage

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64
Q

Constant power terminal can also be called?

A

Powered at all times terminal

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65
Q

If there is damage to the cladding sheath on a optic fibres, what is the repair?

A

Cannot be repaired, must be replaced

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66
Q

In a system with LEDs can electromechanical flashers be used?

A

No, there isn’t enough current draw

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67
Q

What controls a vehicles back up lights?

A

Transmission-mounted switch
or
ECU

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68
Q

Describe Solenoid

A

An electromagnetic device - changes electrical energy into linear movement

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69
Q

What are the three categories of solenoids?

A

Discrete
Proportional
Latching

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70
Q

Does the return spring in a discrete solenoid hold the plunger in a relaxed position or in a fully extended position?

A

Relaxed

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71
Q

What are the two positions of a discrete solenoid?

A

Fully Retracted
or
Fully Extended

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72
Q

What could result if the sleep door is left unlatched for a long period of time? (uses a discrete solenoid)

A

It could overheat and melt insulation

Making the solenoid useless

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73
Q

A proportional solenoid has how many positions?

A

infinite

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74
Q

If the voltage increases in a proportional solenoid what happens to the magnetic field?

A

Also INCREASES

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75
Q

What controls the voltage signal to a proportional solenoid?

A

ECU

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76
Q

What controls a latching solenoid?

A

Current-reversing circuit

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77
Q

Describe self-induction

A

Producing a voltage in the coil circuit when current flow stops

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78
Q

How can switch contact arcing be prevented?

A

Install a high value resistor in parallel with the solenoid coil
or
Clamping diode (self-discharge diode)

79
Q

What does a DC motor use to produce a rotary mechanical motion?

A

Electricity and magnetism

80
Q

A conductor that is bent into a U shape is also called?

A

An Armature

81
Q

in a DC motor what do the stationary brushes that contact the split rings connect to?

A

Cables to a battery

82
Q

A device that produces electricity from rotary mechanical motion is a?

A

Generator

83
Q

The voltage that a dc motor produces is called a?

A

Counter Electromotive Force (CEMF)

84
Q

If you reverse polarity in a PM motor, what will happen?

A

Reverse the direction of rotation

85
Q

A shunt motor can be referred to as?

A

Parallel wound direct current motor

86
Q

True or False

A shunt motor can regulate its own speed?

A

TRUE

87
Q

Where are parallel wound direct current motors used?

A

Fan Blower Motor

-Where uniform speed and low starting torque are wanted

88
Q

Field wound motors can change direction of rotation with no special features?

A

NO you need to add extra switches and make internal motor wiring connections

89
Q

What must be done to a DC motor to reduce speed?

A

Resistors connected in series

90
Q

If a DC motor has two shunt windings, one high resistance and one low, how many speed options can be made?

A

High, Medium and Low

91
Q

If a component is on 100% of the time what is its duty cycle?

A

100% duty cycle

92
Q

If a component is off 20% of the time what is its duty cycle?

A

80% duty cycle

93
Q

How many ways can cruise control be shut off, as per CMVSA?

A

Truck Braking, Clutch Position and dash mounted switch

in an auto trans vehicle there might only be two

94
Q

What does a battery isolation switch help prevent?

A

Discharging of the battery while the truck is parked

95
Q

What must a tech do when bypassing the battery isolation switch?

A

Install fuses on both the negative and positive leads to protect the wiring harness

96
Q

What can be used to reduce or eliminate interference or static noise?

A

Install a series coil (filter choke) OR

parallel-connected capacitor

97
Q

Do permanent magnet direct current motors provide constant or variable torque?

A

Constant torque

98
Q

What are the electromagnets that supply the magnetic field called?

A

Field Coils

99
Q

The iron core the field coils are wound around is called?

A

Pole Shoes

100
Q

How are turn signal flashers connected into the turn signal light circuit?

A

In Series connection

101
Q

List the three types of Solenoids

A

Discrete
Proportional
Latching

102
Q

What makes the latching solenoid very different from the other two solenoid types?

A

The latching solenoid does not return to its normal state by spring pressure. The magnets hold it to one position or the other

103
Q

What does solenoid do with the electrical energy sent to it?

A

Make it into Linear Movement

104
Q

How many positions are available on a discrete solenoid?

A

Only TWO (2)

105
Q

True or False

A discrete solenoid works well with long periods of operation.

A

False

106
Q

How many positions does a proportional solenoid have?

A

Inifinite

107
Q

What allows a proportional solenoid to be used continuously?

A

Fine diameter copper windings

108
Q

True or False

Solenoids need non-permeable cases

A

True

109
Q

What is used to prevent self induction on a solenoid?

A

High value resistor in parallel or clamping diode (self-discharge diode)

110
Q

What does a Direct Current motor use to produce rotary mechanical motion?

A

Electricity and magnetism

111
Q

CEMF stands for?

A

Counter Electromotive force

112
Q

If a field wound DC motor has too much mechanical resistance what will happen?

A

High Current creates high heat and can burn out circuit

113
Q

When replacing a DC motor what should the technician be aware of?

A

Motor must be the correct size to give the correct speed

114
Q

In a DC motor what is used in the circuit to avoid the generation of voltage?

A

Blocking diode

115
Q

Electricity takes what path?

a) path of most resistance
b) path of least resistance

A

Path of least resistance

116
Q

Why are permanent DC motors favorable?

A

Low Maintenance
Reliable
Constant torque
High-load application

117
Q

A permanent magnet DC motor uses what to limit speed?

A

CEMF and load on the motor

118
Q

How is rotation reversed on a PM DC motor?

A

Reverse polarity to the armature

119
Q

True or False

Parallel wound DC motors can regulate their own speed?

A

True

120
Q

What are the three ways to control DC motor speed?

A

Variable electrical resistance
Multiple shunt windings
PWM

121
Q

Indirect gauges can receive a signal in two ways, what are the two signal types?

A

Analog
OR
Digital

122
Q

How are direct acting gauges connected to the component they are monitoring?

A

connected directly to source

123
Q

What are three tyoes of analog gauges?

A

Balancing coil gauge
Stepper motor gauge
Air core Gauge

124
Q

ICU stands for?

A

Instrument control unit

125
Q

What is in a stepper motor gauge that allows it to generate a PWM?

A

Microprocessor

126
Q

What is used to make ONE step into many MICRO steps?

A

a gear reduction

127
Q

Indirectly operated electrical gauges require WHAT to transmit a signal to the dash mounted gauge?

A

Sending units

128
Q

True or False

A positive type coefficient thermistor’s resistance increase as temperature increases

A

TRUE

129
Q

What happens to resistance in a negative type coefficient thermistor as temperature increases?

A

Decreases

130
Q

A thermistor is what kind of resistor?

A

Variable - to temperature

131
Q

Anti-Slosh Module helps with what?

A

Minimizes the gauge pointer fluctuation as liquid moves around in tank

132
Q

True or False

A fuel level sending unit does not need calibration

A

False, may need calibration before or after install

133
Q

What gauges can determine the condition of the trucks electrical system?

A

ammeter and voltmeter

134
Q

Why are fuses used in dash circuits?

A

to avoid dash fires

135
Q

A shunt ammeter uses heavy gauge cable or light gauge cables between the alternator and the battery?

A

Heavy gauge cable

136
Q

With a shunt ammeter what is now possible?

A

cables to the dash gauge can be small gauge

137
Q

Dash Digital ammeters use what? (2 things)

A

hall effect sensor

intergrated circuit amplifier

138
Q

When the alternator is not producing what will the gauge show?

A

Negative - showing the discharge

139
Q

Speedometers indicate what?

A

vehicle speed in Km\h or MPH

140
Q

What are the two speed sensor options on a transmission output shaft?

A

Rotating permanent magnet or Stationary permanent magnet

141
Q

SAE stands for?

A

Society of automotive engineers

142
Q

What does SAE do for electronic control systems?

A

Develop and set the standards

143
Q

Backbone is also referred to as?

A

data bus

144
Q

Nodes have what kind of addresses?

A

Unique address

145
Q

DIP stands for?

A

Dual in-line package

146
Q

What must be calculated before calibrating the speedometer?

A

Pulse per mile (PPM)

147
Q

The DIP switch’s purpose is what when the speedometer directly receives the speed signal from the speed sensor?

A

Calibrate electronic speedometers

148
Q

PPM is found with what information?

A

M - tire revolutions per mile
Ra - rear axle ration
N - number of chopper teeth on tone ring

149
Q

How many chopper teeth on a tone ring are normal?

A

16 or 11

150
Q

on a J-1939-15/CAN2.0 (on highway/off road) what is the normal speed of the data link?

A

250 kb/s

151
Q

If a system has a twisted pair (unshielded) what is the communication speed most likely to be?

A

less than 10 kb/s

152
Q

A tachometer circuit sometimes connects to what other circuit?

A

Hour meter circuit

153
Q

Baud rate can be defined as?

A

Speed of the data transfer over the network (kb/s)

154
Q

What do twisted pairs of wires that are shielded prevent?

A

Electromagnetic interference EMI

155
Q

Fibre optic cables can communicate at what speeds?

A

1 Mb/s to 10 Mb/s

156
Q

What is the maximum length of a stub?

A

one metre

157
Q

A branch is a segment of data link that branches off the back bone and connects to each ________?

A

Node

158
Q

An ECM can also be considered a ______________ on the data link?

A

Node

159
Q

What connects all the multiplexed components of a vehicle system?

A

Data bus

160
Q

A slower, less reliable network is usually because there is no ________________?

A

Protocol

161
Q

What are the two common protocols in heavy duty vehicles?

A

J1587 and CAN

162
Q

CAN stands for?

A

Controller area network

163
Q

CAN provides a serial communications protocol, meaning?

A

That all the information sent on the network is in sequence

164
Q

True or False

Data links only provide the transmissions of input signals between nodes and diagnostic scan tools?

A

FALSE

inputs and outputs

165
Q

Without topology are control modules created equal or gives priorities?

A

Without topology all modules are created EQUAL

166
Q

Data links that have terminating resistors communicate at what baud rate?

A

250 Kb/s

167
Q

A large diameter shunt winding has what kind of resistance?

A

Low resistance

168
Q

A small diameter shunt winding has high resistance causing what kind of speed?

A

Low speed in the parallel wound DC motor

169
Q

What does cruise control need to function?

A

ECM and operator input

170
Q

How many LEDs can be burnt on a ray before the light is considered bad (failed)?

A

1/4 of LEDS in ray

171
Q

Where in the message frame is the checksum?

A

Appears at the end of the message and is one Byte long

172
Q

Identify the order of a SAE J1939 CAN 2.0B message frame.

A

Arbitration field - Control Field - Data Field - CRC Field -ACK - End of Frame

173
Q

CRC stands for?

A

Circular reference check

174
Q

ACK stands for?

A

Acknowledge field

175
Q

Three consecutive recessive bits make up what in a J1939 message?

A

End of frame portion (terminates message)

176
Q

Is the J1939 communicate at a faster speed or slower speed than the J1587 system?

A

FASTER

177
Q

If a J1939 message is not terminated what phenomenon will result?

A

Standing Waves

178
Q

Reflections can cause major problems within the communications system because?

A

They corrupt the signal of the messages on the data link

179
Q

What ohms value do J1939 resistors have?

A

120 ohms

180
Q

What is the DISADVANTAGE to using LED lights in colder climates than incandescent?

A

incandescent lamps give off heat, melting snow/ice off lamps

181
Q

What is an advantage to using LEDs instead of incandescent lamps? (time)

A

LEDs turn on faster than incandescent

182
Q

What is the purpose of the DRAIN wire on a J1939 system?

A

To reduce EMI, grounds to battery

183
Q

Protocol is what in a multiplex system?

A

Language

184
Q

In a system with Topology, describe priorities

A

Topology has all nodes as equals, priorities are sent in the message

185
Q

How many pins does a J1587/1708 system need?

A

6 PIN

186
Q

How many pins are needed on a J1939 system?

A

9 PIN

187
Q

What is the best way to test a fuel sender unit?

A

Ohmeter - power off

188
Q 
True or False
The bulkhead control module can only control one other module?
A

False, can control many modules

189
Q

What and where are _____ and ______ installed in an alternator circuit to reduce noise and interference?

A

In series coil (filter choke) - noise and interference

In parallel - connected capacitor (on the power lead) - interference (voltage surges)

190
Q

In a dash that has fibre optics supplying light to the gauges, what could cause ALL the gauges to be dark?

A

Source light is out

191
Q

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?

A

The cladding sheath is torn

192
Q

What is frequency of a speed sensor measured in?

A

Hertz

193
Q

What is the amplitude of a speed sensor measured in?

A

Voltage AC

Heavy Equipment Technician Period 4 (13 decks)

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