Which of the following is the most common source of abnormal noises arising from the air conditioner?

Which of the following is the first step in the diagnostic process for air-conditioning systems?

A __________ is connected to the air-conditioning refrigerant ports before the performance test begins.

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?

Which of the following is NOT a method of leak testing? Select one:

Flushing with __________ may be necessary for some components, as this removes moisture-laden oil and some contaminated oil. Select one:

If nitrogen testing is the leak test method to be performed, what step would you proceed to next? Select one:

What is the act of removing the refrigerant called? Select one:

The type of refrigerant must remain the same because cross-contamination will create a(n) __________. Select one:

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 __________.

The __________ is normally inspected when high-side pressures are too high and the system is not cooling well.

When cleaning the condenser, what, aside from the shop air, can be used to remove the debris?

Technician A says to determine that the drain tube is clogged by allowing the A/C system to run while observing the drain tube for water drops. Technician B says the drain tube is housed next to the condenser. Who is correct?

Technician A says that the cabin air filter is a lifetime filter that requires cleaning, but not replacement. Technician B says the cabin air filter should be replaced typically twice per year. Who is correct?

Clogs in the drain tube should be removed by __________ the drain tube. Select one:

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:

What gauge is used in conjunction with the mechanical pressure gauge on your air-conditioning machine? Select one:

What detector is sometimes called a "sniffer?" Select one:

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?

Which of the following is considered electrical friction?

Technician A says that if one branch of the circuit is broken, current continues to flow in the other branches in parallel connection. Technician B says if one branch of the circuit is broken, the current flow will be stopped. Who is correct?

Technician A says a more complex circuit than a series circuit arrangement is a parallel circuit. Technician B says that on paper, the schematic diagram of a parallel circuit resembles a ladder. Who is correct?

Technician A says a wiper motor circuit is a common example of a combination circuit. Technician B says that, typically, the power and control circuits are in parallel, but the loads are in series. Who is correct?

An open circuit has what type of resistance?

Which of the following mathematical equations is obtained when Watt’s and Ohm’s laws are combined?

Technician A says operating at 12 volts in comparison to using 24 volts gives an electrical system greater reliability. Technician B says that compared to a 24-volt system, the size of components can be reduced for a 12-volt system. Who is correct?

What is generally an unwanted by-product of resistance?

Which of these faults in the circuit would result in the circuit becoming intermittent?

How are the power supply, circuit protection, and control device typically connected in a combination circuit?

Technician A says that when a circuit defect is caused by an opening in the electrical pathway, excessive current can flow. Technician B says a grounded circuit will not cause a fuse to burn. Who is correct?

Technician A states that a type 3 circuit breaker remains tripped until the operator manually resets it. Technician B states that type 3 circuit breakers are automatically resetting breakers. Who is correct?

All of the following are classifications of circuit malfunction, EXCEPT:

__________ circuit breakers can be a non-cycling type that reset by removing power from the circuit.

What mechanism is used to ensure that a pressure-sensitive switch latches into position regardless of the operator speed?

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?

Calculate the voltage of a circuit that is rated as 1.5 amps and has a resistance of 2 ohms across it.

Which of these statements about PPTC fuses is NOT true?

During the test of a circuit protection device, the power is available only to the circuit protection device and not to the load. Technician A states that this is an indication of an open fuse. Technician B states that this is an indication of a good fuse. Who is correct?

Which of these mathematical statements describes Watt’s law? Select one:

According to conventional electrical theory, which way does electricity move in most commercial vehicle chassis? Select one:

Consider an atom with 28 protons and 29 electrons. It could be accurately described as: Select one:

Consider the principle of Joules heating. Which of the following units of electrical measurement changes when amperage increases through a circuit? Select one:

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:

Technician A says AC circuits are used in virtually all chassis circuits because a battery can easily store and supply AC current. Technician B says DC current is used to power hybrid drive electric motors. Who is correct?

Technician A says AC's main advantage is that it can be transmitted farther distances with less resistance and little voltage drop. Technician B says the term resistance is used with AC circuits as well as DC circuits. Who is correct?

Technician A says electronic circuits use less amperage and often process electrical signals rather than perform the work of lighting, heating, and mechanical movement. Technician B says electrical circuits usually conduct higher amounts of current through heavier conductors and commonly operate high current flow devices, such as solenoids, relays, motors, lights, and more. Who is correct?

Technician A says metals typically have lots of easily moved electrons, which make them good conductors. Technician B says liquids cannot function as a conductor. Who is correct?

Technician A says that Ohm's Law predicts increased circuit resistance as voltage increases. Technician B says Ohm's Law predicts both amperage and voltage in a circuit vary depending on circuit resistance. Who is correct?

Technician A says that Ohm's Law predicts that a conductor's resistance increases when amperage increases. Technician B says that Joule's Law predicts a small amount of resistance in a circuit becomes much greater when amperage increases. Who is correct?

Technician A says that the resistance of a circuit or load determines the amount of amperage flowing through it. Technician B says that the voltage in a circuit determines its resistance. Who is correct?

Technician A says the forces of electrostatic repulsion and attraction move electrons through a circuit. Technician B says the movement of electrons and protons from one atom to another is called electricity. Who is correct?

Technician A says there are two theories of current flow: the electron theory and the conventional theory. Technician B says it is only important to remember that current flow is described by both concepts. Who is correct?

Technician A says today's electrical system components are no longer separated into distinct systems. Technician B says networking electrical system components add new vehicle features that can enhance safety, performance, and passenger comfort. Who is correct?

The concept of amperage refers best to the following:

Which measurement of electrical flow measures electron movement in number of electrons past a single point in a circuit per second of time?

Which of the following descriptions best describes the electrical term, polarity?

Which of the following electrical terms is most closely associated with "electrical friction"?

Which of the following terms best describes the electrical pressure that causes current to flow in a circuit?

Which of the following types of matter are expected to have the fewest electrons in the outer valence orbital?

A circuit that has a current flow of 2 amps and resistance of 12 ohms would have a voltage of __________.

Electrical circuits use _________ conductors, while electronic circuits use __________ conductors.

Electronic circuits use __________ amperage and often __________ electrical signals. Select one:

Electronic circuits use electricity flowing through __________. Select one:

If an atom has more electrons than it does protons, it is called __________. Select one:

It was observed that a wire that conducts electricity had broken wires under the insulation. Technician A says that its resistance would be greater than what it was earlier (before the damage of the wire). Technician B says that the wire’s resistance would be less than what it was before the occurrence of the damage. Who is correct? Select one:

Technician A says that electrical circuits usually conduct lower amounts of current and electronic circuits operate with higher amounts of current. Technician B says electrical circuits conduct higher amounts of current and electronic circuits conduct lower amounts of current. Who is correct? Select one:

Technician A says that electronic circuits consist of integrated circuits. Technician B says electrical circuits consist of integrated circuits. Who is correct?

The speed of electron travel through a conductor from atom to atom is known as _________.

__________ is the term used that describes the number of electrons moving in a circuit.

__________ is the unit for measuring electrical power.

Technician A says all matter is made up of atoms. Technician B says atoms are made up of electrons and protons only. Who is correct?

Technician A says that amperage describes the average speed of one or many electrons moving in an electric circuit. Technician B says that amperage is the quantity of electrons passing through a circuit. Who is correct?

Technician A says that test instruments, such as Amp/Volt/Resistance (AVR) machines, are designed presuming current flow is conventional. Technician B says that such instruments use electron theory. Who is correct?

What is the unit for AC frequency called?

Which of the following uses a single driver in a lead truck and has multiple driverless trucks that follow the lead truck?

Which of these electrical components protects electrical circuits from heating and burning caused by excessive amperage?

Which of these electrical terms is very much similar to the mechanical term "friction"?

Which of these instances causes the flow of electricity?

Which of these statements is false about direct current (DC)?

__________ has a mandate to have radar-based collision-avoidance systems in vehicles.

__________ is the term for liquids that conduct electric current.

Technician A says conductors are materials that hold electrons tightly and prevent electron movement. Technician B says because multiple electrons in its outer shell are held loosely by the nucleus, copper makes an excellent conductor. Who is correct?

When a gas conducts electricity, it is said to be in a ___________ state.

Which of the following prevents the flow of electricity?

Which of these statements is NOT true about electric current?

__________ is a term that describes a property of electrical particles that either repels or attracts other electrical particles.

All of the following are examples of telematics, EXCEPT:

In an electric circuit or any electrical device, the push and pull producing the movement of electricity is supplied by __________.

Technician A says increasing sophistication of heavy-duty electrical systems includes radar-based collision-avoidance systems. Technician B says increasing sophistication includes hybrid electric powertrain and telematics. Who is correct?

Technician A states that a proton charge attracts another proton’s charge. Technician B states that an electron charge repels another electron’s charge. Who is correct?

Beginning in 2017, the NHTSA requires __________ on all class 7 and 8 vehicles.

Technician A says that the air conditioning control module receives information from the vehicle data link for chassis air pressure in the air reservoirs to protect the air conditioning system components. Technician B says that the battery voltage is critical to protect air conditioning system components. Who is correct?

Air conditioning systems absorb heat from a cab interior through a(n) __________.

Air conditioning systems transfer heat to the atmosphere using a(n) __________.

Although refrigerants are relatively safe, they are considered to be __________.

Hydrofluoro-olefin (HFO)-based refrigerant has a GWP that is __________% lower than R134a.

A condenser located in the cab removes heat and transfers it to the atmosphere via the evaporator. Who is correct? Select one:

Which of the following is a replacement for Freon? Select one:

Which of the following was produced by reacting carbon tetrachloride with fluorine gas? Select one:

A comfortable vehicle environment reduces driver __________. Select one:

How do the late-model vehicles help maintain a cleaner and dust-free cab interior? Select one:

Moisture condensed on a cold __________ helps remove dirt and other air particulates. Select one:

Technician A says that the safety benefit of air conditioning is its ability to clean and filter air entering the operator compartment. Technician B says that the safety benefit of air conditioning is to remove dust, pollen, and particulate matter from the air. Who is correct?

The air conditioning system can operate to clear the windows with greater efficiency than a heated ___________ alone.

Which measurement of heat best explains the amount of heat from the sun potentially entering the cab?

Which of the following holds true about air conditioning system?

Which of the following is a safety benefit of air conditioning?

___________ is a metric term for the amount of energy required to raise the temperature of 1 gram of water by 1°C.

Heat measured using a thermometer is referred to as __________ heat.

Heating is regulated by circulating engine coolant through an in-cab heat exchanger called a __________.

The heating capacity of a truck’s heating system is between 50,000 and 80,000 BTU/h. Technician A says that the heating capacity in buses exceeds 126,000 BTU/h. Technician B says that the heating capacity of a truck’s heating system is approximately the same as an average heating furnace of a small-sized home. Who is correct?

What is the measuring unit required to change one pound of water to one pound of ice or vice versa?

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?

Which of the following best explains conduction? Select one:

Which of the following holds true about latent heat of fusion? Select one:

Which of the following is one of the rules that summarizes the basic principles of refrigeration? Select one:

Which of the following units can reduce idle time by using an electrically operated compressor? Select one:

Technician A says heat always moves toward a colder object. Technician B says using a refrigerant compressor and a condenser, which is a type of heat exchanger, enables the process of latent heat removal from the refrigerant through condensation. Who is correct? Select one:

Technician A says removing heat from an object or substance is simple, because cold always moves toward a warmer object. Technician B says all that is necessary for cooling is to provide an even warmer substance for cold to flow into. Who is correct? Select one:

The process of evaporating refrigerant is completed by using __________.

Which of the following holds true for latent heat of condensation?

Which of the following holds true for latent heat of evaporation?

The liquid does not simply change temperature, but changes state, and much more heat is evacuated by the refrigerant. __________ liquid leaves the condenser.

Consider a rotatory compressor having cylindrical-shaped housings and enclosing multiple pistons. Which of the following is the primary advantage of rotatory piston compressors?

Rotary compressors in trucks will have a displacement of __________ cubic inches. Select one:

Technician A says that mobile HD air conditioning compressors have refrigerant condensers that enable the compressor to easily shut off when compressor operation is not required. Technician B says that mobile HD air conditioning compressors have an electromagnetic clutch that enables the compressor to easily shut off when compressor operation is not required. Who is correct? Select one:

The __________ is one of the principal parts of refrigeration system. Select one:

What are the three basic types of air conditioning compressors that can be used to build pressure exceeding 350 psi? Select one:

What are the two major types of expansion devices used in commercial vehicle air conditioning systems? Select one:

Which of the following holds true for refrigeration systems? Select one:

Which of the following is a primary determinant of the system’s ability to remove heat? Select one:

Which of the following is NOT a common compressor control? Select one:

Technician A says the thermostatic expansion valve controls refrigerant flow by the action of a spring-loaded control valve. Technician B says that usually about an 20 F temperature difference between evaporator inlet and outlet is required to open the valve. Who is correct? Select one:

The condition where excess refrigerant floods the evaporator is called evaporator __________. Select one:

The purpose of the pressure cycling switch is to maintain an evaporator pressure of approximately __________. Select one:

The thermal expansion valve device lowers the pressure of the warm, high-pressure liquid refrigerant entering the __________.

The thermal expansion valve spring is generally adjusted to provide for a temperature differential of __________.

Which of these holds true for H-Valve thermal expansion valve (TXV) operation?

An important component in the cooling action of the evaporator is the __________ located in the evaporator housing.

Technician A says the thermostatic expansion valve meters to ensure all the liquid refrigerant has changed to a vapor by the time it reaches the evaporator outlet. Technician B says if too much refrigerant is allowed to enter, the evaporator floods and this results in poor cooling. Who is correct?

The coldest air temperature from the evaporator is when the blower is operated at its ________ speed.

Which of the following holds true for evaporators? Select one.

Which of the following is NOT correct concerning the evaporator? Select one.

A glass insert at the receiver-dryer outlet allows the technician to detect __________. Select one.

Technician A says accumulators often incorporate an important diagnostic aid—the refrigerant sight glass. Technician B says accumulators collect liquid refrigerant leaving the evaporator and separate vapor from liquid before the refrigerant enters the compressor. Who is correct? Select one.

The __________ is located in the low-pressure side of the system. Select one.

The accumulator has functions similar to the __________.

Which of the following is the primary function of the receiver-dryer?

Refrigerant must dissolve __________ and move it through the system.

The most common refrigerant, R-134a, has a GWP of __________.

What is the application of tetrafluoroethane?

What is the viscosity of the oil used in reciprocating piston compressors?

When released into the atmosphere, HFO-1234yf decomposes, giving it a lifetime of __________.

Which one of these is an ideal refrigerant property? Select one:

Technician A says that the venting of refrigerant to the atmosphere is prohibited by law, so it is necessary to use a high-pressure cutout switch. Technician B says that the venting of refrigerant to the atmosphere is prohibited by law, so it is necessary to use a low-pressure cutout switch. Who is correct? Select one:

Technician A says the thermostatic switch, also called the cold switch, is an condenser temperature-sensing switch. Technician B says there is only one type of thermostatic switch used on commercial vehicles. Who is correct? Select one:

Technician A says the trinary switch is mounted in the low-pressure refrigerant line. Technician B says it is known as a trinary switch because of its three sets of internal contacts. Who is correct? Select one:

The air conditioning controls are necessary to __________. Select one:

What switch has three sets of internal contacts? Select one:

When a predetermined low charge is sensed in CCOT (orifice-tube) systems, the ________ switch stops compressor operation. Select one:

Which of the following holds true for the ambient temperature switch? Select one:

The correct answer is: It is designed to delay evaporator operation when it senses a very low outside air temperature. Which one of these is used with either the CCOT or TXV metering systems? Select one:

__________ is when the thermostatic sensor prevents the compressor from operating if it detects an evaporator condition. Select one:

__________ is claimed to eliminate the problems that make the air-conditioning system one of the highest maintenance expense items for most

__________ prevents low-voltage compressor clutch burnout.

Technician A says the APADS control system is composed of an electronic control module, four smart pressure switches, and a conventional condenser thermostat. Technician B says the control module operates as the auxiliary air-conditioning system control. Who is correct?

The thermostat contacts close when the temperature is greater than __________.

Whenever a system fault is detected, the __________.

Which of the following best explains APADS? Select one:

On late-model vehicles, air door actuators, as well as the blower motor, use (a) ________. Select one:

When discussing the function of the air distribution system, Technician A says a separate air conditioning request switch is used to enable dehumidification of air when humidity levels in the cab are high. Technician B says as a safety feature, when placed in defrost mode, most systems automatically switch on the air conditioning system to dehumidify airflow to the windshield. Who is correct? Select one:

When discussing the function of the air distribution system, Technician A says actuators for the cab air door controls are operated by brush-type stepper motors providing low power consumption. Technician B says a Hall-effect sensor is built into many motors to provide position feedback to the microcontroller to verify the actuators are correctly positioning. Who is correct? Select one:

Which of the following holds true for the vent defrost door? Select one:

Which one of the following is a standard mode of air distribution? Select one:

Which of the following functions of an air conditioning system is directly related to safe vehicle operation? Select one:

Which of the following is the most recent category or type of air conditioning refrigerant? Select one:

Technician A says that outside air flows over the fins of the condenser transferring heat from the refrigerant, causing it to convert from a gas to a liquid. Technician B says that the condenser compressor pressure helps convert hot gas to a liquid in the condenser. Who is correct? Select one:

Consider a truck with 36,000 BTU cooling capacity. How many tons of air conditioning does this system have? Select one:

Technician A says that the low-pressure cut out switch is connected in series with the compressor clutch electrical circuit. Technician B says that when a low refrigerant charge is sensed, the switch opens and prevents compressor operation. Who is correct?

Technician A says that the thermostatic expansion valve controls refrigerant flow through the action of a variable orifice control valve. Technician B says that approximately a 5° F (15° C) temperature difference between evaporator inlet and outlet is required to open the valve. Who is correct?

Which measurement of heat best describes the amount required to produce a change of state?

What would be the equivalent pressure in "psig" units be for a 3-psia measured at sea level?

Technician A says that the refrigerant HFO-1234YF is currently used in vehicle air conditioning systems. Technician B says that the refrigerant R-143a is used in vehicle air conditioning systems. Who is correct?

Technician A says that air conditioning systems transfer cold from the atmosphere and into the passenger compartment. Technician B says that air conditioning systems dehumidify and clean air passing through the evaporator. Who is correct?

How is lubricating oil circulated in an air conditioning system?

Technician A says that heat energy in an air conditioning system travels from cold to hot. Technician B says that the air conditioning system's condenser removes heat from the cab and transfers it to the atmosphere via the evaporator. Who is correct?

Which of the following statements is correct concerning the TXV expansion device?

How many cylinders does a rotary compressor typically have that is used in a highway tractor?

Which of the following devices senses evaporator pressure to control the cycling of the air conditioning clutch in a Navistar CCOT system? Select one:

99. Technician A says that increasing refrigerant pressure causes its temperature to increase. Technician B says increasing refrigerant pressure causes it to vaporize. Who is correct?

100. Technician A says that reducing refrigerant pressure causes the refrigerant to absorb heat. Technician B says reducing refrigerant pressure causes it to evaporate. Who is correct?