Deck 35: Heavy-Duty Heating, ventilation, and Air Conditioning Systems

Question 1

A container of R-134a has a pressure of 70 psig.What is its approximate temperature?

A) 70 degrees Fahrenheit
B) 85 degrees Fahrenheit
C) 95 degrees Fahrenheit
D) 105 degrees Fahrenheit

Answer 1

A

Question 2

What would happen to liquid refrigerant if exposed to ambient temperatures under no pressure?

A) boil to a vapor
B) freeze to a solid
C) condense to a liquid
D) molecularly decompose

Answer 2

A

Question 3

Both the high-side and the low-side gauge readings are abnormally low.Which of the following could cause this condition?

A) system low on refrigerant
B) moisture in the system
C) obstruction in the system
D) all of the above

Answer 3

A

Question 4

At which stage in a typical refrigeration cycle does low-pressure liquid become a low-pressure gas?

A) compression stage
B) condensation stage
C) expansion stage
D) evaporation stage

Question 5

If the low-side pressure is too high and the high-side pressure is too low,what is the most likely cause?

A) damaged compressor
B) moisture in the system
C) blend-air door stuck
D) 80/20 door stuck

Question 6

While examining a R-134a system through the sight glass,the refrigerant appears to be cloudy.Which of the following would probably be the cause?

A) low refrigerant level
B) high refrigerant level
C) contamination caused by desiccant breakdown
D) undercharge of oil in the system

Question 7

In which stage of a typical refrigeration cycle does high-pressure gas change state to become a high-pressure liquid?

A) compression stage
B) condensation stage
C) expansion stage
D) evaporation stage

Question 8

Which of the following terms is used as a metric measurement of heat energy?

A) BTUs
B) joules
C) watts
D) farads

Question 9

Which of the following terms is used as the U.S.standard measurement of heat energy to rate A/C specifications?

A) BTU's
B) joules
C) calories
D) watts

Question 10

How is the A/C compressor effective cycle managed in truck air conditioning systems?

A) electronically
B) thermostat
C) centrifugal clutch
D) all of the above

Question 11

When should a stem-type service valve be front-seated?

A) during normal operation
B) when taking gauge readings
C) whenever the compressor has to be isolated
D) all of the above

Question 12

Which of the following refrigerants is commonly used in current trucks?

A) R-12
B) R-22
C) R-134a
D) propane

Question 13

When is the only time that both hand valves of a manifold gauge set should be open at the same time?

A) when reading both pressures
B) during system evacuation
C) during system charging
D) never open both at the same time

Question 14

Which of the following is NOT a function of a receiver/dryer in an air conditioning system?

A) filters particles from liquid refrigerant
B) removes moisture from liquid refrigerant
C) receives low-pressure gas from the evaporator
D) stores liquid refrigerant until it is needed at the evaporator

Question 15

Which air conditioning component functions to separate the high- and low-pressure sides of the system?

A) expansion valve
B) condenser
C) evaporator
D) receiver dryer

Question 16

Which of the following statements is true?

A) heat travels from a cooler area to a warmer area
B) when liquids evaporate,heat is released
C) when a gas condenses to a liquid,heat is absorbed
D) when a liquid boils,heat is absorbed

Question 17

Which of the following components functions to protect an A/C system from either under-pressure or over-pressure?

A) binary switch
B) trinary switch
C) TXV
D) Both A and B

Question 18

Which of the following air conditioning components is located in the truck cab?

A) compressor
B) condenser
C) evaporator
D) all of the above

Question 19

Which of the following failures would NOT result in both the high- and low-side pressures to read too high?

A) damaged compressor
B) system overcharged
C) large amount of air in the system
D) overcharge of oil

Question 20

Which of the following best describes the principle of latent heat of vaporization?

A) the heat energy required to change a liquid to a vapor without raising its temperature
B) the heat released from a vapor as it changes to a liquid without changing its temperature

Question 21

Which refrigerant is most commonly used in current reefer trailers?

A) R-12
B) R-22
C) R-134a
D) propane

Question 22

Technician A says that all matter on earth contains some heat energy.Technician B says that a substance with no heat energy would have a temperature of minus 459 Fahrenheit or absolute zero.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 23

How many states of matter are identifiable under normal atmospheric conditions?

A) one
B) two
C) three
D) four

Question 24

Which of the following is NOT a function of a truck air-conditioning system?

A) removes moisture from cab air
B) removes pollen and particulate from cab air
C) cools cab air
D) conditions underhood ram air

Question 25

What federal legislation controls mobile refrigerant standards,usage,and disposal?

A) Clean Air Act
B) National Highway Traffic Safety Administration
C) Federal Motor Vehicle Safety Standards
D) Highway Traffic Act

Question 26

The amount of heat energy required to raise 1 lb of water by 1 degree Fahrenheit is known as one (1):

A) kilopascal
B) Btu
C) joule
D) horsepower

Question 27

Technician A says that heat is always surrendered by a cold material to a warmer one.Technician B says that 1 Btu is approximately 1000 joules when converted to the metric system.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 28

Which of the following components is a heat exchanger?

A) compressor
B) receiver/dryer
C) condenser
D) thermostat

Question 29

Which of the following best describes the branch of physics known as thermodynamics?

A) behavior of cold
B) behavior of heat
C) study of air-conditioning systems
D) study of heat exchangers

Question 30

What is the heat energy required to change a substance from one state to another,known as?

A) calorific value
B) thermal coefficient
C) latent heat
D) kinetic energy

Question 31

Technician A says that when a mineral oil installed into a R-134a system it will not dissolve into the refrigerant and can clog up circulation.Technician B says that all R-12 systems use mineral oils.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 32

Technician A says that when a substance is frozen to a solid state,heat energy is released.Technician B says that when ice melts,heat energy is released.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 33

If you were to boil a kettle of water while at high altitude,which of the following would be true?

A) water would boil at 212 degrees Fahrenheit
B) water would boil at a lower temperature than 212 degrees Fahrenheit
C) water would boil at a higher temperature than 212 degrees Fahrenheit

Question 34

An ideal refrigerant should be:

A) non-combustible
B) non-toxic
C) have convenient freeze/ boil temperatures
D) all of the above

Question 35

Which of the following is true of the refrigerant exiting the condenser in an A/C circuit?

A) exits cooler than it entered and in a gaseous state
B) exits warmer than it entered and in a gaseous state
C) exits cooler than it entered and in a liquid state
D) exits warmer than it entered and in a gaseous state

Question 36

Technician A says that after retrofitting an R-12 truck A/C system to R-134a,the system can be serviced using R-12 service equipment.Technician B says that a more powerful vacuum pump is required to evacuate a HFC-134a system.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 37

What color is an R-134a refrigerant container?

A) white
B) light blue
C) cream
D) light pink

Question 38

Technician A says that ozone (O₃)in the upper atmosphere is caused by CFCs and harms the environment.Technician B says that CFCs leach oxygen atoms from ozone (O₃)reducing it to O_2. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 39

Where is the coldest point in a properly functioning A/C circuit?

A) compressor
B) condenser
C) evaporator
D) expansion valve

Question 40

What color is an R-12 refrigerant container?

A) white
B) light blue
C) cream
D) light pink

Question 41

What type of compressor clutch is likely used on a current A/C compressor?

A) stationary coil type clutch
B) rotating coil type clutch
C) centrifugal type clutch
D) wet type clutch

Question 42

Technician A says that both R-12 and R-134a refrigerants are lighter than air when in a gaseous state.Technician B says that using an electronic leak detector is not always the best way of sourcing a leak because its sensitivity can make identifying the location difficult.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 43

What is the rule of thumb for adding oil to a truck A/C system after replacing one of its major components?

A) add 1 oz per component
B) add 2 oz per component
C) add 4 oz per component
D) add 1 lb per component

Question 44

Technician A says that bubbles can be seen through the sight glass on an R-134a system even when it is operating normally.Technician B says that many R-134a truck A/C systems are no longer fitted with sight glasses.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 45

Which of the following describes the term subcooling in an A/C system?

A) additional cooling of refrigerant at the lower portion of condenser after it liquidizes
B) additional cooling of refrigerant at the lower portion of condenser after it vaporizes
C) any refrigerant temperatures that are lower than 0 degrees Fahrenheit

Question 46

Technician A says that a compressor receives low pressure liquid refrigerant and discharges high pressure gas.Technician B says that an orifice tube or TXV separates the high pressure and low pressure sections of an A/C circuit.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 47

Technician A says that suction lines in an A/C system can be easily identified because they are usually warm to touch.Technician B says that discharge lines are usually cool to touch and of larger diameter than suction hoses.

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 48

Which of the following is a key advantage of a swashplate type A/C compressor?

A) much lower cost
B) greater longevity
C) consumes less power to drive it compared with an equivalent sized piston compressor
D) easier to troubleshoot system problems

Question 49

What type of gloves should NEVER be worn when servicing A/C systems?

A) rubber gloves
B) leather gloves
C) cotton gloves
D) vinyl gloves

Question 50

Which of the following best explains why a vacuum has to be pulled for a considerable time period when evacuating an A/C system?

A) vacuum pump first lowers the boil point of moisture,then extracts it
B) vacuum pump takes longer to pull out liquid moisture
C) vacuum is less effective than pressure at expelling moisture

Question 51

Technician A says that an A/C system pressure relief valve can be set to trip at values of 400 psi or higher.Technician B says that if a system pressure relief valve trips,the high-pressure cut-off switch must have failed.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 52

Technician A says that a muffler is usually located on the discharge side of a compressor.Technician B says that a muffler can sometimes be located on the intake side of a compressor.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 53

What is the most sensitive type of refrigerant leak detector?

A) soapsuds
B) flame type propane
C) phosphor dye and ultra-violet light
D) electronic

Question 54

Which of the following types of compressors are used in truck A/C systems?

A) swashplate
B) crank-actuated piston
C) rotary vane
D) all of the above

Question 55

A cylinder of nitrogen shows a gauge pressure of 2000 psi.What should the pressure be reduced to before purging a truck A/C system

A) 1000 psi
B) 400 psi
C) 300 psi
D) 200 psi

Question 56

If it were possible to connect a 1-pound disposable refrigerant can to the high side of an A/C system,what would most likely result?

A) contents of the can would immediately be sucked into the system
B) refrigerant on high side would be pulled into the can
C) can might explode
D) high side hoses would explode

Question 57

What must be done with an A/C system before replacing any system component?

A) vent the refrigerant to atmosphere
B) recover all refrigerant to an A/C station
C) equalize low side and high side pressures
D) ensure there is sufficient refrigerant to recharge the system

Question 58

When the blend air door on a truck A/C system is allowing both air conditioned and heated air to mix,how is the system being operated?

A) defrost mode
B) default mode
C) maximum cooling
D) maximum heating

Question 59

What happens when refrigerant leaking from an AC circuit comes into contact with an open flame?

A) it contaminates
B) it may combust
C) poisonous phosgene gas may result
D) all of the above

Question 60

Which of the following accurately describes the function of the fusible plug used in an A/C system?

A) provides a measure of fire safety in the event of an underhood fire
B) melts and releases engine coolant if temperature exceeds 245 degrees Fahrenheit
C) melts and releases refrigerant if temperature exceeds 230 degrees Fahrenheit
D) provides a measure of explosion protection when ambient temperatures climb to 115° F

Question 61

What fuel is usually used in a current truck supplemental coolant heater?

A) gasoline
B) propane
C) kerosene
D) diesel fuel

Question 62

When a current truck uses an electronically controlled A/C system,which of the following is usually true?

A) networked to J1939 data bus
B) controller is SA 25/MID 190
C) A/C compressor clutch is an ECU output
D) all of the above

Question 63

Technician A says that a cause of both high low- and high-side A/C system pressure readings,is an overcharged refrigerant condition.Technician B says that a cause of high low-side and high,high-side A/C system pressures is a system that is heavily over-charged with oil.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 64

Technician A says that a truck A/C electronic control unit is usually networked to the chassis data bus in todays trucks.Technician B says that the thermostat is an output device for the A/C controller.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 65

What are the advantages of a truck diesel powered auxiliary power unit (APU)?

A) generate up to 4000 watts of electricity
B) consume much less fuel than operating the truck engine
C) can oparate both the cab/bunk heating and cooling systems when the truck is stationary
D) all of the above