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WorksheetsACR-206 Final Exam Review
Total questions: 139
Worksheet time: 1hrs 10mins
The __________ typically disables the A/C system if pressures fall below 10 psi (69 kPa).
Low-pressure switch
TXV (thermal expansion valve)
Heater control
High-pressure relief
Which of the following is the most common source of abnormal noises arising from the air conditioner?
Evaporator
Compressor
Accumulator
Muffler
Which of the following is the first step in the diagnostic process for air-conditioning systems?
System pressure test
Diagnosis of faults
Performance testing
Check for codes in the computer
A __________ is connected to the air-conditioning refrigerant ports before the performance test begins.
Thermometer
Manifold pressure gauge set
Micron gauge
Safety switch
Which of the following works very well for testing discharged systems or for pre-checking for a leak after repairs have been made and before recharging the system?
Fluorescent dye
Oxygen
Compressed Air
Nitrogen
Which of the following is NOT a method of leak testing? Select one:
Vacuum testing
Electronic leak detection
Dye testing
Nitrogen testing
Flushing with __________ may be necessary for some components, as this removes moisture-laden oil and some contaminated oil. Select one:
Nitrogen
Compressed air
Refrigerant gas
Lubrication oil
If nitrogen testing is the leak test method to be performed, what step would you proceed to next? Select one:
Diagnosing
Charging
Evacuation
Reclaiming
What is the act of removing the refrigerant called? Select one:
Reclaiming
Flushing
Recharging
Recycling
The type of refrigerant must remain the same because cross-contamination will create a(n) __________. Select one:
Hazardous substance
Strong enough magnetic pull
Inefficient cooling system
Increased energy consumption
System malfunction
When cleaning a condenser, shop air or a water hose may be used to remove the debris, but be careful to not fold over the __________.
Fins
Blades
Coils
Tubes
The __________ is normally inspected when high-side pressures are too high and the system is not cooling well.
Condenser
Evaporator
Compressor
Expansion Valve
When cleaning the condenser, what, aside from the shop air, can be used to remove the debris?
Water hose
Drain tube
Oil filter
Nitrogen purging
Clogs in the drain tube should be removed by __________ the drain tube. Select one:
Blowing air into
Spraying water into
Flushing refrigerant gas through
Passing nitrogen gas through
Using a vacuum pump
Which of the following is used to determine what the high- and low-side pressures should be at a given outside temperature and humidity in a properly functioning system? Select one:
Reclaim/recycle machine
PT chart
Anemometer
Micron gauge
What gauge is used in conjunction with the mechanical pressure gauge on your air-conditioning machine? Select one:
Micron
Vacuum
Manifold
High-side
What detector is sometimes called a "sniffer?" Select one:
Dye leak detector
Carbon monoxide detector
Electronic leak detector
Sealant detector
An air-conditioning compressor pulley or bearing may need service when which of the following is detected from the bearing as the engine is running?
Loss of pressure
Vibration
Noise
Leakage
Which of the following is considered electrical friction?
Voltage
Resistance
Amperage
Current
An open circuit has what type of resistance?
Infinite resistance
Zero resistance
Low resistance
Variable resistance
Which of the following mathematical equations is obtained when Watt’s and Ohm’s laws are combined?
Power = Voltage × Amperage
Power = Voltage / Resistance
Voltage = Power × Amperage
Voltage = Amperage / Power
What is generally an unwanted by-product of resistance?
Amperage drops
Light
Heat
Low amperage
Which of these faults in the circuit would result in the circuit becoming intermittent?
Fuse blown
Loose connections
Unintended path for current flow
Unintended ground
How are the power supply, circuit protection, and control device typically connected in a combination circuit?
Series
Parallel
Wye formation
Delta formation
All of the following are classifications of circuit malfunction, EXCEPT:
Opened
Closed
Shorted
High resistance
__________ circuit breakers can be a non-cycling type that reset by removing power from the circuit.
Type 1
Type 2
Type 3
Type 4
What mechanism is used to ensure that a pressure-sensitive switch latches into position regardless of the operator speed?
Slow-acting mechanism
Spring-loaded mechanism
Momentary-contact mechanism
Over-center mechanism
Which of the following statements is true when the lead of a test light or common lead of the voltmeter is connected to chassis ground?
A good fuse shows a very high resistance.
A blown fuse has 0 volts on one side of the fuse.
A good fuse has battery voltage on only one side of the fuse.
A blown fuse has the same voltage on both sides.
Calculate the voltage of a circuit that is rated as 1.5 amps and has a resistance of 2 ohms across it.
3.5 V
0.5 V
3 V
0.75 V
Which of these statements about PPTC fuses is NOT true?
They are also known as resettable fuses.
They are thermistor-like electronic devices.
Resistance in the devices suddenly increases to thousands of ohms.
Current trip ratings for PPTC devices range from 20 mA to 50 mA.
Which of these mathematical statements describes Watt’s law? Select one:
Power = Voltage × Amperage
Power = Voltage × Resistance
Voltage = Power × Amperage
Voltage = Amperage / Power
According to conventional electrical theory, which way does electricity move in most commercial vehicle chassis? Select one:
From the negative ground, through the load, then back to the battery
From the "hot" insulated wire, through the load, then back to the battery
From negative charge potentials to positive charge potentials
Electrons leave the negative terminal of the battery and return through the positive post
Consider an atom with 28 protons and 29 electrons. It could be accurately described as: Select one:
Aluminum
Negatively charged
Positively charged
Anion
Consider the principle of Joules heating. Which of the following units of electrical measurement changes when amperage increases through a circuit? Select one:
Resistance
Voltage
Farads
Capacitance
Consider two objects with electrical charges. Objects A and B both repel one another. What is the polarity of the charges found on the objects? Select one:
A is positive, B is negative.
A and B are both positive.
A is negative, B is positive.
A is negative, B is neutral.
The concept of amperage refers best to the following:
The speed of electrical impulse
The force of electrical impulse
The quantity of electron movement
The pressure of the electrical impulse
Which measurement of electrical flow measures electron movement in number of electrons past a single point in a circuit per second of time?
Coulomb
Voltage
Resistance
Amperage
Which of the following descriptions best describes the electrical term, polarity?
The electrical pressure in a circuit
The direction of electron movement
The force of electrostatic attraction
The direction of electrostatic repulsion
Which of the following electrical terms is most closely associated with "electrical friction"?
Amperage
Current
Voltage
Resistance
Which of the following terms best describes the electrical pressure that causes current to flow in a circuit?
Resistance
Amperage
Voltage
Current
Which of the following types of matter are expected to have the fewest electrons in the outer valence orbital?
Conductors
Insulators
Semi-conductors
Resisters
A circuit that has a current flow of 2 amps and resistance of 12 ohms would have a voltage of __________.
24 volts
24 watts
6 volts
6 watts
Electrical circuits use _________ conductors, while electronic circuits use __________ conductors.
Longer; shorter
Larger; smaller
Smaller; larger
Electronic circuits use __________ amperage and often __________ electrical signals. Select one:
Less; process
More; amplify
High; distort
Low; filter
Electronic circuits use electricity flowing through __________. Select one:
Transistors
Resistors
Capacitors
Inductors
If an atom has more electrons than it does protons, it is called __________. Select one:
A negative ion
A positive ion
A neutral atom
A proton-rich atom
The speed of electron travel through a conductor from atom to atom is known as _________.
Current
Amplitude
Resistance
Power
Voltage
__________ is the term used that describes the number of electrons moving in a circuit.
Resistance
Current
Voltage
Power
Amperage
__________ is the unit for measuring electrical power.
Watts
Volts
Ohms
Amperes
What is the unit for AC frequency called?
Ohm
Hertz
Voltage
Watt
Which of the following uses a single driver in a lead truck and has multiple driverless trucks that follow the lead truck?
Radar system
Platooning
Lidar
Cruise control
Which of these electrical components protects electrical circuits from heating and burning caused by excessive amperage?
Fuse
Resistor
Capacitor
Inductor
Which of these electrical terms is very much similar to the mechanical term "friction"?
Voltage
Amperage
Wattage
Resistance
Which of these instances causes the flow of electricity?
Positive ion placed near neutral ion
Positive ion placed near negative ion
Negative ion placed near negative ion
Negative ion placed near neutral ion
Which of these statements is false about direct current (DC)?
DC flows only in one direction.
DC flows from a negative to a positive.
DC flows when electrons are alternatively pushed and pulled.
DC voltage on a graph produces a straight line.
__________ has a mandate to have radar-based collision-avoidance systems in vehicles.
Europe
North America
Asia
Australia
__________ is the term for liquids that conduct electric current.
Ion
Insulator
Impurity
Electrolytes
When a gas conducts electricity, it is said to be in a ___________ state.
Liquid
Plasma
Solid
Gaseous
Which of the following prevents the flow of electricity?
Nucleus
Conductor
Capacitor
Insulator
Which of these statements is NOT true about electric current?
Electric current is produced by the flow of positive charges.
Electrostatic forces are essential to produce the flow of electrical current.
A proton repels another proton.
Electric current can be converted into different forms of energy.
__________ is a term that describes a property of electrical particles that either repels or attracts other electrical particles.
Electrostatic force
Resistance
Current
Electromagnetism
Voltage
All of the following are examples of telematics, EXCEPT:
Vehicle to vehicle
Vehicle to remote location
Internet, satellite, or cell
Remote fueling
In an electric circuit or any electrical device, the push and pull producing the movement of electricity is supplied by __________.
Electromagnetism
Electrostatic force
Friction
Photoelectric effect
Beginning in 2017, the NHTSA requires __________ on all class 7 and 8 vehicles.
Collision avoidance
Stability control
Telematics
GHG legislation
Air conditioning systems absorb heat from a cab interior through a(n) __________.
Condenser
Evaporator
Compressor
Blower
Air conditioning systems transfer heat to the atmosphere using a(n) __________.
Condenser
Compressor
Evaporator
Filter
Blower
Although refrigerants are relatively safe, they are considered to be __________.
Penetrants
Absorbents
Irritants
Suffocants
Corrosives
Hydrofluoro-olefin (HFO)-based refrigerant has a GWP that is __________% lower than R134a.
89.7
80
33.2
50
99.7
Which of the following is a replacement for Freon? Select one:
R-502
R-22
R-11
R-134a
Which of the following was produced by reacting carbon tetrachloride with fluorine gas? Select one:
HFO
Freon
HCHC
R-135a
A comfortable vehicle environment reduces driver __________. Select one:
Vigor
Fatigue and distraction
Certainty and tranquility
Toughness
How do the late-model vehicles help maintain a cleaner and dust-free cab interior? Select one:
Equipped with an air ventilator located at the cab air inlet
Equipped with an air filter located at the cab air inlet
Equipped with an air compressor located at the cab air inlet
Equipped with an air filter located at the cab air outlet
Moisture condensed on a cold __________ helps remove dirt and other air particulates. Select one:
Evaporator
Condenser
Radiator
Heater
The air conditioning system can operate to clear the windows with greater efficiency than a heated ___________ alone.
Evaporator
Condenser
Defroster
Separator
Which measurement of heat best explains the amount of heat from the sun potentially entering the cab?
Heat load
Planck's law of radiation
One calorie
Kelvin
Which of the following holds true about air conditioning system?
The compressor is located before the heater core.
Before moisture-laden outside air reaches the heater core, the air conditioning system dehumidifies the air.
Warm, wet air is blown over the windows to improve visibility more quickly.
The condenser is positioned in parallel with the heater core airflow.
Which of the following is a safety benefit of air conditioning?
Ability to clean and filter air entering the passenger compartment
Reduces driver vigor
Ability to osmose the air entering the operator compartment
Ability to assimilate dirt
___________ is a metric term for the amount of energy required to raise the temperature of 1 gram of water by 1°C.
Specific heat
Calorie
Joule
Watt
Heat measured using a thermometer is referred to as __________ heat.
Sensible
Latent
Specific
Radiant
Heating is regulated by circulating engine coolant through an in-cab heat exchanger called a __________.
Heat core
Radiator
Condenser
Evaporator
What is the measuring unit required to change one pound of water to one pound of ice or vice versa?
144 BTU
1 BTU
12,000 BTU/h
126,000 BTU/h
Which measurement of heat best describes the quantity of heat required to produce a change of state from a solid to a liquid or a liquid to a gas?
Latent heat
Radiant heat
Specific heat
Sensible heat
Which of the following best explains conduction? Select one:
Conduction takes place when heat is transferred through liquid.
Conduction takes place when heat is transferred through a solid.
Conduction refers to the transfer of heat through a gas.
Conduction takes place through a medium such as a gas or vacuum.
Which of the following holds true about latent heat of fusion? Select one:
The amount of heat a substance must absorb to undergo a temperature change of 1°F
The amount of energy required to raise the temperature of 1 gram of water by 1°C
The process of changing water to ice
Describes the quantity of heat required to produce a change of state from a solid to a liquid
Which of the following is one of the rules that summarizes the basic principles of refrigeration? Select one:
Heat can pass into anything that has more heat.
If there is no change of state, there must be a transfer of heat.
Latent heat of vaporization is used to absorb small amounts of heat inside the cab.
To refrigerate is to remove heat.
Which of the following units can reduce idle time by using an electrically operated compressor? Select one:
Auxiliary air conditioning unit
Cabin air conditioning unit
Latent heat unit
Compressor unit
The process of evaporating refrigerant is completed by using __________.
Removal of heat from refrigerant
Specific heat
Latent heat of evaporation
Latent heat of condensation
Which of the following holds true for latent heat of condensation?
Using a refrigerant compressor and a condenser enables the process of latent heat removal.
Reducing the pressure of the refrigerant causes the refrigerant to cool.
Compressing the gas and sharply increasing its pressure causes the refrigerant to convert into a solid.
If compressed gas is circulated through a condenser, large amounts of specific heat are transferred from the gas to the atmosphere.
Which of the following holds true for latent heat of evaporation?
Reducing the pressure of the refrigerant causes the refrigerant to boil.
Cabin air is the best source of coolant.
Cooler cabin air results from the heat transfer into the condensing refrigerant.
The liquid does not simply change temperature, but changes state, and much more heat is evacuated by the refrigerant. __________ liquid leaves the condenser.
Low-pressure, cold
High-pressure, cold
Low-pressure, warm
High-pressure, warm
Consider a rotatory compressor having cylindrical-shaped housings and enclosing multiple pistons. Which of the following is the primary advantage of rotatory piston compressors?
Minimization of noise
Maximization of vibration
Maximization of harshness (NVH)
Minimization of compressor energy
Rotary compressors in trucks will have a displacement of __________ cubic inches. Select one:
3 to 6
7 to 15
15 to 19
20 to 23
The __________ is one of the principal parts of refrigeration system. Select one:
Condenser
Belt
Switch
Piston
What are the three basic types of air conditioning compressors that can be used to build pressure exceeding 350 psi? Select one:
Piston, centrifugal compressor, and rotatory screw
Piston, rolling piston, and rotatory screw
Piston, rotary vane, and scroll
Piston, centrifugal compressor, and diaphragm
What are the two major types of expansion devices used in commercial vehicle air conditioning systems? Select one:
Thermostatic expansion valve (TXV) and a fixed-orifice tube
Suction valve and a fixed-orifice tube
TVX and a concentric orifice tube
Suction valve and discharge valve
Which of the following holds true for refrigeration systems? Select one:
They add moisture to the air passing through the evaporator.
The compressor is an engine-driven pump that decreases refrigerant pressure.
Air conditioning and refrigeration systems transfer heat from the cab and passenger compartment to the air stream outside the vehicle.
The compressor’s capacity to remove refrigerant
Which of the following is a primary determinant of the system’s ability to remove heat? Select one:
The evaporator’s capacity to add refrigerant
The evaporator’s capacity to remove the clutch
The compressor’s capacity to move refrigerant
The compressor’s capacity to remove refrigerant
Which of the following is NOT a common compressor control? Select one:
Thermostatic switch
Pressure modulator switch
Trinary switch
High-pressure cutout switch
The condition where excess refrigerant floods the evaporator is called evaporator __________. Select one:
Frost
Freezing
Sub-zero
Pressure regulation
The purpose of the pressure cycling switch is to maintain an evaporator pressure of approximately __________. Select one:
29 psi
49 psi
39 psi
59 psi
The thermal expansion valve device lowers the pressure of the warm, high-pressure liquid refrigerant entering the __________.
evaporator
compressor
condenser
receiver
The thermal expansion valve spring is generally adjusted to provide for a temperature differential of __________.
42°F to 14°F
4°F to 16°F
6°F to 18°F
8°F to 20°F
Which of these holds true for H-Valve thermal expansion valve (TXV) operation?
TXV meters the refrigerant into the evaporator at a variable rate.
It maintains the evaporator at low temperature and pressure.
Spring tension acting on the orifice ball regulates the quality of refrigerant flow.
Inlet temperature also can change the position of the linkage.
An important component in the cooling action of the evaporator is the __________ located in the evaporator housing.
Blower fan
Receiver drier
Condenser fan
Driver evaporator module
The coldest air temperature from the evaporator is when the blower is operated at its ________ speed.
Molecular
Slowest
Fastest
Road
Which of the following holds true for evaporators? Select one.
When a gas evaporates, it must radiate a tremendous amount of heat to change state.
The source of heat is cold moist cabin air blowing under the surface of the evaporator.
The evaporator is a heat exchanger located inside the cab or passenger compartment.
The serpentine coil evaporator is constructed from a metal coil mounted parallel to thick heating fins.
Which of the following is NOT correct concerning the evaporator? Select one.
The evaporator is a heat exchanger located inside the cab or passenger compartment containing the chamber where refrigerant boils and converts to a vapor.
The evaporator does not remove moisture from the cabin air.
Like the condenser, the evaporator has a couple of common constructions.
The serpentine coil evaporator is constructed from a metal coil mounted in a series of thin cooling fins.
A glass insert at the receiver-dryer outlet allows the technician to detect __________. Select one.
Undercharged refrigerant
Low heat loads
Potential moisture
Line corrosion
The __________ is located in the low-pressure side of the system. Select one.
Dryer
Accumulator
Compressor
Condenser
The accumulator has functions similar to the __________.
Condenser
Compressor
Evaporator
Receiver dryer
Which of the following is the primary function of the receiver-dryer?
To absorb any moisture in the air conditioning system
To serve as a storage reservoir for refrigerant
The drying agent excludes any potential moisture from the refrigerant.
At higher engine speeds and low heat loads, the receiver-dryer floods with liquid.
Refrigerant must dissolve __________ and move it through the system.
Acidity
Dust
Moisture
Contaminants
Oil
The most common refrigerant, R-134a, has a GWP of __________.
1400
1200
1000
1700
What is the application of tetrafluoroethane?
CFC replacement for low-temperature commercial refrigeration
Automotive and residential refrigeration systems
R-22 CFC replacement
R-12 replacement
What is the viscosity of the oil used in reciprocating piston compressors?
10-30w
15-40w
85-100w
90-120w
When released into the atmosphere, HFO-1234yf decomposes, giving it a lifetime of __________.
11 days
1 year
10 years
100 years
Which one of these is an ideal refrigerant property? Select one:
A high boiling point and freezing point
A high sensible heat and low boiling point
A low freezing point and high sensible heat
A low specific heat and high latent heat
The air conditioning controls are necessary to __________. Select one:
Adjust operator comfort levels in the cab of the vehicle
Expose major components to damage
Increase fuel efficiency
Reduce engine noise
Enhance vehicle speed
What switch has three sets of internal contacts? Select one:
Trinary
Thermostatic
Pressure-cycling
Ambient temperature
When a predetermined low charge is sensed in CCOT (orifice-tube) systems, the ________ switch stops compressor operation. Select one:
Pressure-cycling
Low-pressure cutout
High-pressure cutout
High-pressure fan
Which of the following holds true for the ambient temperature switch? Select one:
It is designed to delay evaporator operation when it senses a very low outside air temperature.
At cold ambient temperatures, this sensing switch closes its electrical contacts.
The ambient temperature switch is a cabin air temperature-sensing switch.
The ambient temperature switch contacts open when a preset temperature is reached, normally 42°F to 70°F.
__________ is when the thermostatic sensor prevents the compressor from operating if it detects an evaporator condition. Select one:
High-pressure cutout
High-pressure reset
Freeze-up protection
Diagnostic cutout
__________ is claimed to eliminate the problems that make the air-conditioning system one of the highest maintenance expense items for most
APADS
CCOT
TXV
NVH
__________ prevents low-voltage compressor clutch burnout.
Compressor lubrication period
High-pressure reset
Voltage stabilizer
Compressor cycle limit
Compressor hold-off period
The thermostat contacts close when the temperature is greater than __________.
38°F
28°F
40°F
37°F
Whenever a system fault is detected, the __________.
Air conditioning protection and diagnostic system (APADS) receives inputs from the vehicle data link
Compressor is not allowed to run
Air conditioning system is turned off
APADS broadcasts diagnostic information over the data bus
Which of the following best explains APADS? Select one:
The unit receives input from two trinary switches and a thermostat.
Operates both air conditioning controls and analog controls
Extends the lifespan of the air conditioning system on medium- and heavy-duty trucks
The output signals are interpreted by control logic.
On late-model vehicles, air door actuators, as well as the blower motor, use (a) ________. Select one:
Brushless DC stepper motor
Temperature bled door
Condensate-free windshield
Blower fan
Which of the following holds true for the vent defrost door? Select one:
Mixes the proportion of inside and outside air drawn into the blower motor
Directs air to the floor
Directs air to vent or defrost ducts
Blends air conditioning and heater core air flow
Which one of the following is a standard mode of air distribution? Select one:
Defrost mode
MIN air conditioning mode
High level mode
Level mode
Which of the following functions of an air conditioning system is directly related to safe vehicle operation? Select one:
It reduces driver fatigue.
It cleans and filters air.
It keeps the operator and passengers comfortable.
It is automatically activated in defrost mode.
Which of the following is the most recent category or type of air conditioning refrigerant? Select one:
Freon
R-134a
HFO
HCHC
Consider a truck with 36,000 BTU cooling capacity. How many tons of air conditioning does this system have? Select one:
1 ton
2 tons
3 tons
4 tons
Which measurement of heat best describes the amount required to produce a change of state?
Latent
Sensible
Radiant
Convection
What would be the equivalent pressure in "psig" units be for a 3-psia measured at sea level?
0 psig
3 psig
-3 psig
17.7 psig
How is lubricating oil circulated in an air conditioning system?
Refrigerant dissolves oil like a solvent and circulates oil.
The compressor pumps oil.
It is stored in each component needing oil for lubrication.
The velocity of refrigerant gas carries oil.
Which of the following statements is correct concerning the TXV expansion device?
The TXV expansion device lowers the pressure of the warm, high-pressure liquid refrigerant entering the evaporator and allows the refrigerant to expand to greater volume.
An orifice in the TXV creates a pressure differential, forming the dividing point in the low side of the air conditioning system.
The high-side pressure and low-side temperature regulate the valve operation.
It must be combined with a high-side pressure switch to regulate evaporator temperature.
How many cylinders does a rotary compressor typically have that is used in a highway tractor?
2-4
4-8
5-10
6-12
Which of the following devices senses evaporator pressure to control the cycling of the air conditioning clutch in a Navistar CCOT system? Select one:
Thermistors
Pressure transducer and high-pressure switch
Cab thermostatic switch
CAN controls
