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
D. When a liquid boils, heat is absorbed
Which of the following best describes the principle of latent heat of vaporization?
A. Heat energy required to change a liquid to a vapor without raising its temperature
B. Heat released from a vapor as it changes to a liquid without changing its temperat
A. Heat energy required to change a liquid to a vapor with our raising its temperature.
At which stage of a typical refrigeration cycle does low pressure liquid become a low pressure gas?
D. Evaporation stage
Which of the following air conditioning components is located in the truck cab?
C. Evaporator
In which stage of a typical refrigeration cycle does high pressure gas change state to become a high pressure liquid?
B. Condensation stage
How is A/C compressor effective cycle managed in truck air conditioning systems?
A.Electronically
B.With a thermostat
C.Centrifugal clutch
D. all of the above
All of the above
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 refriger
Receives low pressure gas from the evaporator.
Which air conditioning component functions to separate the high and low pressure sides of the system?
A. Expansion valve
Which of the following components functions to protect an A/C circuit from either under pressure or over pressure?
A. binary switch
B. trinary switch
While examining an R-12 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. excess o
C. contamination caused by the desiccant breakdown.
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
A. damaged compressor
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
D. all of the above
If the low side pressure is too high and the high side pressure is too low, what is the most likely cause?
Damaged compressor
Which of the following refrigerants is commonly used in current trucks?
C. R-134a
Which of the following is Not a function of a truck air conditioning system?
A. removes moisture from the cab air
B. removes pollen and particulate from cab air
C. cools cab air
D. conditions underhood ram air
D. conditions underhood ram air
Which of the following best describes the branch of physics known as thermodynamics?
A. Behavior of cold
B. Behavior of heat
B. Behavior of heat
Which of the following components is a heat exchanger?
A. compressor
B. receiver/dryer
C. condensor
D. thermostat
C. condensor
The amount of heat energy required to raise 1 lb. of water by i degree F. is known as one?
BTU
What is the heat energy required to change a substance from one state to another, known as?
C. latent heat
Tech A says that when a substance is frozen to a solid state heat energy is released. Tech B says that when ice melts, heat energy is released. Who is correct?
Tech A
An ideal refrigerant should be?
A. non combustable
B. non toxic
C. have convenient freeze/boil temperatures
D. all of the above
D. all of the above
Which refrigerant is most commonly used in current reefer trailers?
B. R-22
Where is the coldest point in a properly functioning A/C circuit?
C. evaporator
If you were to boil a kettle of water while on top of a mountain, what would be true?
B. water would boil at a lower temperature than 212 degrees fahrenheit.
What federal legislation controls mobile refrigerant standards, usage and disposal?
A. clean air act
What color is an R-12 refrigerant container?
A. white
What color is an R-134a refrigerant container?
B. light blue
Which of the following is true of the coolant exiting the condenser in an A/C circuit?
C. exits cooler than it entered and in a liquid state.
Tech A says that a compressor receives low pressure liquid refrigerant and discharges high pressure gas. Tech B says that an office tube or TXV divides the high pressure and low pressure sides of an A/C circuit. Who is correct?
Tech B
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
D. all of the above
Which of the following is a key advantage of a swashplate type A/C compressor?
A. much lower cost
B. greater longevity
C. requires half the power to drive it compared with equivalent sized piston compressor.
D. easier to troubleshoot
C. requires half the power to drive it compared with equivalent sized piston compressor
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
A. stationary coil type clutch
Tech A says that an A/C safety pop off valve can be set to trip values as high as 400 psi. Tech B says that if a safety pop off valve trips,the high pressure cut off switch must have failed. Who is correct?
Both Techs
Which of the following accurately describes the function of the fusible plug used in an A/C system?
C. melts and releases refrigerant if temperature exceeds 230 degrees Fahrenheit.
Tech A says that suction lines in an A/C system can be easily identified because they are usually warm to touch. Tech B says that discharge lines are usually cool to touch and a larger diameter than suction?
Neither Techs
Tech A says that a muffler is usually located on the discharge side of the compressor. Tech B says that a muffler can sometimes be located on the intake side of the compressor. Who is correct?
Both Techs
What type of gloves should never be worn when servicing A/C systems?
B. leather gloves
What happens when refrigerant comes into contact with an open flame?
C. poisonous phosgene gas can be formed.
Tech A says that bubbles can be seen through the sight glass on an R-134a system even when it is operating normally. Tech B says that many R-134a truck A/C systems are no longer fitted with glasses. Who is correct?
Both Techs
Tech A says that both R-12 and R134a is lighter then air when in a gaseous state. Tech 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
Tech B only
Why does a vacuum have to be pulled for a considerable time period when evacuating an A/C system?
A. vacuum pump first lowers boil point of moisture then pulls out the moisture vapor.
What MUST be done with an A/C system before replacing any system components?
B. recover all refrigerant to an A/C station
A cylinder of nitrogen shows a gauge pressure of 2000 psi. What must the pressure be reduced to before purging a truck A/C system?
D. 200 psi.
What is the rule of thumb for adding oil to a truck A/C system after replacing one of its major components?
B. add 2 oz. per component
When the blend 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
Tech A says that a cause of high low side and high side A/C system is a slightly overcharged with refrigerant condition. Tech B says that a cause of high low side and high side A/C system pressures is a heavily over charged with oil condition. Who is corr
Both Techs
What fuel is usually used in a current truck supplemental coolant heater?
D. diesel fuel
What are the advantages of struck diesel powered auxiliary power unit?
A. generate up to 4000 watts of electricity
B. consumes 1/4 or less fuel than running the truck engine
C. can run both the cab/bunk heating and cooling systems when the truck is statio
D. all of the above
When the truck uses an electronically controlled A/C system, which of the following is usually true?
A. networked to J1939 data bus
B. controller is MID-190
C. A/C compressor clutch is an ECU output.
D. all of the above
D. all of the above.
Technician A says that ozone (O3) in the upper atmosphere is caused by CFC's and harms the environment. Technician B says that CFC's leach oxygen atoms from ozone (O3) reducing it to (O2). Who is correct?
Tech B only.
Which position on the climate control panel should the driver select to avoid having the air-conditioning compressor turn on?
A. HEAT
B.DEFROST
C.AC
D.Both A and B
A. Heat
What is the function of the desiccant bag inside an accumulator?
It captures and stores moisture
The vehicles thermostat stuck open, what will occur?
No hot air will come out of the vents when heat is selected.
The vehicles thermostat stuck closed, what will occur?
The vehicle will overheat.
Ambient air temp sensor senses what air?
The outside air on the vehicle.
Blend doors are actuated by what?
Vacuum and electricity.
Blower motor resistor is bad on a vehicle, what will occur?
the highest setting will work, the lower settings will not or will stay at full blast when a lower setting is selected.
High and low sides of the AC system read low, what could be the issue?
Low refrigerant charge
Compressor clutch clearance is called?
Air gap.
Why do we pull a vacuum on an AC system?
We pull a vacuum on an A/C system to remove most if not all moisture.
If the compressor fails what other components should you also
compressor we need to replace orifice tube or expansion valve and replace the receiver drier or the accumulator.
A binary switch is?
A low pressure switch
A trinary switch is?
A high pressure switch
A receiver dryer system typically has a sight glass, typically has a sight glass. True or False
True
Both sides on an AC system are reading high, what could be the cause?
To much airing the system, over charge of refrigerant and to much oil was added to the system.
Both sides on the AC system are reading low, what could be the cause?
The system is undercharged, moisture in the system and a blockage in the system.
Low side is high and the high side is low on an AC system, what could be the cause?
The compressor is trash
The smart word for the study of heat and its behavior is called?
Thermodynamics
In the world of semi trucks, what do they call a condenser?
A heat exchanger
What is a BTU (British thermal unit).
The amount of heat energy needed to raise one pound of water one degree Fahrenheit
Where is the coldest point on an AC system?
The evaporator