AC final
O-rings are being discussed. Technician A says that R-134a O-rings are usually black. Technician B says that R-12 O-rings are blue or green. Who is correct?
Neither A nor B
The electromagnetic clutch is being discussed: Technician A says that the clutch will slip if the air gap is too close. Technician B says that the clutch will slip if the belt is close. Who is correct?
Neither A nor B
Technician A says air conditioning is the process of controlling the passenger compartment comfort level. Technician B says the fluid that circulates through an air conditioning system is referred to generically as refrigerant. Who is correct?
Both A and B
Technician A says that it is virtually impossible to insert the seal seat backward when using the appropriate tool. Technician B says that it is almost impossible to remove a seal seat that has been installed backward. Who is correct?
Neither A nor B
Technician A says shop ventilation is not needed when working on new vehicles because new-vehicle emissions are low. Technician B says the shop's ventilation system should be connected to the exhaust pipe if the engine is running. Who is correct?
Technician B only
The electronic variable displacement compressor is based on what type of compressor design?
Swash plate compressor design
Technician A says that when working on a refrigerant system you should work in a well-ventilated area. Technician B says to determine the type of refrigerant used in a system, a refrigerant identifier should be used prior to servicing the vehicles refrigerant system. Who is correct?
Both A and B
A customer complains of the passenger compartment temperature always being too hot, cold, or not changing as the temperature range is changed on the control panel. On an electronic mode door actuator (motor) system all of the following could cause this problem, except:
Faulty actuator
Technician A says that the accumulator is on the high-pressure side of the refrigerant system. Technician B says that the receiver-drier is attached to the evaporator outlet on the refrigerant system. Who is correct?
Neither A nor B
The heat added to a vapor causing it to become warmer is called:
Superheat
The recommended minimum efficiency of a vacuum pump at sea level atmospheric pressure is being discussed: Technician A says that atmospheric pressure has no effect on efficiency. Technician B says that the greater the vacuum achieved, the better the efficiency. Who is correct?
B only
Technician A says that an evaporator is a heat exchanger. Technician B says that a condenser is a heat exchanger. Who is correct?
Both A and B
The following statements regarding the relationships between the cooling system and air-conditioning -system are all true, except:
Ambient air first passes through the radiator, then the condenser.
Pressure switches are being discussed: Technician A says that a test lamp should never be used to test the operation of a pressure switch. Technician B says that at atmospheric pressure a low - pressure switch should be normally closed. Who is correct?
B only
The airflow path in the case/duct system illustrated in Figure 10-52 is being discussed: Technician A says that airflow is also through the heater core in the cooling mode. Technician B says that airflow is also through the evaporator in the heating mode. Who is correct?
B only
All of the following statements about system evacuation are true, except:
If vacuum does not reach 24 to 26 in. Hg (20.3 to 23.5 kPa absolute), evacuate for a longer time
What does the air conditioning compressor do to the system refrigerant?
Increases its pressure
The purpose of the compressor is to
Pump low-pressure vapor to a high-pressure vapor
All of the following statements about a typical air-¬conditioning system set to MAX cooling are true, except:
The heater coolant flow control valve is open
It is necessary to drain the engine coolant before replacing which component?
The heater core
On a vehicle equipped with and automatic temperature control system the blower motor will not function when the vehicle is first started and heat is selected. Which of the following is the most likely cause?
The system is functioning normally
The blower motor does not run when the HEAT mode is first selected and the engine is cold on a vehicle that is equipped with an automatic temperature ¬control system. Which of the following is the most likely cause?
There is an excessive voltage drop at the blower motor
All of the following conditions could cause poor passenger compartment heating system performance EXCEPT
Thermostat stuck in the closed position.
A manifold and gauge set is attached to an operating air conditioner. The low-side gauge reading is too high and the high-side reading is too low. What could be the problem?
defective compressor
On a system that uses an accumulator what type of metering device is used?
fixed orifice tube
If a thermostat fails in the open position, all of the following will occur, EXCEPT:
loss of coolant.
An undercharged system will show which of the following gauge readings?
low side, low; high side, low
The metering device changes high-pressure liquid into a
low-pressure liquid
Refrigerant enters the compressor as a
low-pressure vapor.
Under normal operating conditions all of the following occurs inside the evaporator, EXCEPT:
The refrigerant changes from a vapor to a liquid.
When the air conditioning system is operating all of the following happens inside the evaporator, EXCEPT:
the refrigerant changes from a vapor to a liquid.
Evaporation is being discussed. Technician A says heat is lost when evaporation occurs. Technician B says the rate of evaporation is not affected by air movement. Who is correct?
B only
To measure and adjust compressor clutch air gap, a _______________ feeler gauge should be used.
nonmetallic
When retrofitting, the proper R-134a charge of ¬refrigerant is about _______________ of the original R-12 refrigerant charge.
90 percent
The least likely cause of an inoperative vacuum motor is:
A defective check valve
A vehicle is brought into the shop with a complaint of weak airflow from all the dash vents. Which of the following is the most likely cause?
A dirty cabin air filter
The temperature fluctuates between hot and cold on a vehicle equipped with an automatic temperature -control system. Which of the following is the most likely cause?
A disconnected in-car temperature sensor aspirator tube
The rear evaporator duct is cooling properly on a vehicle with a rear heating and cooling system, but the front evaporator duct temperature is too warm. What is the most likely cause of this condition?
A misadjusted front blend door
Technician A says that a shutoff-type service valve has a front-seated position. Technician B says that a Schrader-type service valve has a front-seated position. Who is correct?
A only
All of the following statements are true, except:
A refrigerant identifier will identify R-134a at any purity.
An odor from the evaporator may be caused by all of the following, except:
All of the above
When the air-conditioning switch is turned to the OFF position, the compressor clutch stays engaged. Which of the following is the most likely cause?
An electronic thermostat is out of specification
A rattling noise is heard when the engine is running and the air conditioning is off. Technician A says this noise may be caused by too narrow gap between the compressor's armature and rotor. Technician B says a quick accurate test is to see if the clutch is the source is to switch on the air conditioning to see if the noise stops. Who is correct?
Both A and B
If the compressor cycles while charging: Technician A says to place a jumper across the temperature switch. Technician B says to place a jumper across the low-pressure switch. Who is correct?
Both A and B
Refrigerant contamination is being discussed. Technician A says that R-12 with a 5 percent trace of R-22 is considered contaminated. Technician B says that R-12 with a 5 percent trace of R-134a is considered contaminated.
Both A and B
Technician A says a sun load sensor may be tested by placing a dark piece of cloth over sensor while observing data values on a scan tool. Technician B says an infrared temperature sensor may be tested by alternately placing a cold damp towel and a hot damp towel in front of the sensor while observing data values on a scan tool. Who is correct?
Both A and B
Technician A says mode doors may be vacuum operated. Technician B says mode doors may be electrically operated. Who is correct?
Both A and B
Technician A says that O-rings designated for R-12 service do not need to be changed for retrofit. Technician B says that O-rings designated for R-134a service may also be used for R-12 service. Who is correct?
Both A and B
Technician A says that POE is compatible with R-134a. Technician B says that PAG oil is compatible with R-134a. Who is correct?
Both A and B
Technician A says that a slight amount of conditioned air is made available at the defroster duct outlet at all times to prevent windshield fogging. Technician B says that a positive in-vehicle ¬pressure is maintained at all times to prevent exhaust gas infiltration.
Both A and B
Technician A says that the new refrigerant installed must be identified on the retrofit label. Technician B says that the shop that performed the A/C system retrofit must be identified on the retrofit label.
Both A and B
Which of the following desiccants should be used with HFC-134a refrigerant?
Both B and C
An inoperative vacuum motor could be caused by all of the following, except
Mode door cable misadjustment
A technician finds an air-conditioning clutch will not engage. Upon initial testing the compressor is receiving both proper power and ground at the compressor clutch electrical connector; in addition the compressor input shaft turns freely by hand. Which of the following is the most likely cause?
Compressor clutch air gap too large
During normal air-conditioning system operation, the position of the system mode doors:
Depends on the mode selected
When should the cabin air filter be replaced if the vehicle is operated in dusty or high pollution conditions?
Every 15,000 miles
Which of the following is the best description of a pressure switch designated NC?
It is held closed during normal pressure conditions.
What affect does the receiver dryer have on the refrigerant?
It stores some liquid refrigerant.
The retrofit label's background color for R-134a refrigerant is:
Light blue
All of the following are removed from an air-¬conditioning system during evacuation, except:
Lubricant
The following may be used to maintain in-vehicle ¬temperature, except:
Mass airflow sensor
After stabilizing the air-conditioning system, the engine speed is returned to normal. Technician A says this is to reduce airflow across the condenser. Technician B says this is to increase the cooling capacity of the evaporator. Who is correct?
Neither A nor B
Replacement of hoses during retrofit procedures is being discussed. Technician A says hoses need not be replaced unless they are the old-style nonbarrier type. Technician B says hoses need not be replaced unless they are equipped with the old-style O-rings and fittings. Who is correct?
Neither A nor B
Technician A says that a DOT 39 cylinder may be used to temporarily store contaminated refrigerant. Technician B says that, if they are used, DOT 39s must be marked "CONTAMINATED REFRIGERANT" for identification. Who is correct?
Neither A nor B
Which of the following refrigerants may be vented
Neither A or B
Which of the following is not a tool used by the air-conditioning system technician
OBD-5 scanner
During normal comfort control operation with the windows closed, harmful gases are not allowed to enter the vehicle because:
Of a slight in-vehicle positive pressure
A vehicle's automatic temperature control system does not hold the temperature set on the temperature -control assembly. What operation should the technician perform first?
Refer to the appropriate diagnostic fault chart
An odor emitting from the case and duct system may be caused by all of the following, except
Refrigerant gas leak
All of the following may need to be performed as part of a retrofit procedure from R-12 to R-134a refrigerant, except
Replace all air conditioning system hoses with ¬barrier hoses
On an automatic temperature control system that will not hold the temperature set at the control panel, what should the technician do first?
Replace the climate control panel
The following statements about a typical system set to MAX cooling are true, except:
Return air is from vehicle exterior
Electric motor-driven air-conditioning compressors used on hybrid vehicles are based on what compressor design?
Scroll compressor design
Before installation: Technician A says that refrigerant system O-rings should be coated with new refrigerant oil. Technician B says refrigerant system O-rings can be coated with a gasket sealant. Who is correct?
Technician A only
Technician A says cleaning the fresh air inlet should be part of a periodic preventative maintenance schedule. Technician B says debris in the fresh air intake can contaminate the refrigerant. Who is correct?
Technician A only
Technician A says that the electronic leak detector probe should be held directly against a suspected leak area during a leak test. Technician B says that the electronic leak detector requires routine calibration and probe tip inspection and maintenance. Who is correct?
Technician B only
After retrofitting a vehicles air conditioning system from R-12 to R-134a a retrofit label should be affixed under the hood containing the following information, except:
Technicians name and address
A refrigerant retrofit label must contain all of the following except
The amount of R-12 removed from the system
The compressor changes a low-pressure vapor to
a high-pressure vapor.
A vehicle returns to the shop for a repeat failure of the compressor system due to compressor clutch slippage and overheating. Which of the following is the most likely cause?
High resistance in the compressor clutch electrical circuit
The shims shown in the illustration are used to
Adjust the air gap
Electrical testing is being discussed: Technician A says that an analog ohmmeter should not be used to test an electronic circuit. Technician B says that a digital ohmmeter may be used to test any electrical or electronic circuit. Who is correct?
A only
Technician A says an in-car temperature sensor may be tested by measuring its resistance at 70˚F and 80˚F. Technician B says an ambient ¬temperature sensor may be tested by measuring its amperage at 70˚F and 80˚F. Who is correct?
A only
Technician A says that a thermostat is used for temperature control in some systems. Technician B says that a low-pressure control is used for temperature control in some systems. Who is correct?
Both A and B
Technician A says that a trouble code may be displayed on some master control heads. Technician B says that there are provisions for ¬connecting an external scan tool on some systems. Who is correct?
Both A and B
A refrigerant identifier will do all of the following except:
Display the percentage of water vapor (H2O)
All of the following alternate refrigerants are approved for automotive use, except
Duracool 12a
All of the following air-conditioning system sensors are varying resistive sensors except
Infrared Temperature Sensor
The following statements regarding a visual inspection for intermittent faults are all true, except:
Inspect for catastrophic component failure.
When the air-conditioning system is first turned on, a musty odor comes from the vents. What is the most likely cause for this
Mold formation on the evaporator core
Technician A says that a check valve prevents vacuum flow in either direction. Technician B says that a check valve permits vacuum flow in either direction. Who is correct?
Neither A nor B
Technician A says that a red label is required to identify R-134a in an automotive air-conditioning system. Technician B says that a yellow label is used to identify R-12 in an automotive air-conditioning system. Who is correct?
Neither A nor B
The blower motor on a four-speed switched system only functions on the high-speed setting. Which of the following is the most likely cause?
The blower motor ground is faulty
During a refrigerant system performance test it is noticed that both high-side and low-side pressure readings are about the same. Which of the following could be the possible cause?
A faulty compressor clutch.
If the compressor oil has been drained and it shows signs of metallic particles, all of the following should be done, except:
A full charge of heavier refrigeration oil should be added after flushing
Technician A says that up to 20 percent of fresh air provides a means to maintain a positive in-vehicle pressure when the windows are closed. Technician B says this positive pressure is necessary to provide a proper balance of air pressure within the air delivery system. Who is correct
A only
The compressor clutch circuit is being tested. Technician A says if the compressor clutch coil voltage drop is equal to source voltage (battery) then the clutch coil is defective. Technician B says if the test lamp does not light when connected across the clutch's harness terminals, then the problem is probably a shorted clutch coil. Who is correct?
A only
A technician is checking refrigerant system pressures. Both high- and low-side service ports are located on the A/C compressor. When the compressor is engaged, the high-side pressure instantly goes over 375 psig. What is the most likely cause of this condition?
A restricted discharge hose.
An R-134a expansion valve system that is properly charged has the following gauge readings, high-side 150 psig and low-side 42 psig and the ambient air temperature is 85°F. Which of the following is the most likely cause?
A stuck open expansion valve
On a vehicle equipped with front and rear A/C dual evaporator system, the front evaporator cools properly, but the rear evaporator is warm. Which of the following is the most likely cause?
A stuck open rear expansion valve.
All of the follow are true about engine thermostats EXCEPT:
A thermostat should be removed from a system if it is running hot
Technician A says that a vacuum reserve tank helps maintain a vacuum in the system at all times only when the engine is running. Technician B says that the check valve prevents ¬vacuum loss when the engine is stopped. Who is correct?
B only
A leaking evaporator is being replaced. Technician A says the new o-rings should be coated with clean refrigerant oil. Technician B says the some refrigerant oil should be added to the system prior to recharging the system. Who is correct?
Both A and B
Charging the system is being discussed. Technician A says the refrigerant must be weighed (or metered) to obtain a proper charge. Technician B says overcharging the system will reduce its cooling efficiency. Who is correct?
Both A and B
During a routine fluid level inspection a radiator is found to be low on coolant. Technician A says that a faulty radiator cap could be the cause. Technician B says that a cracked radiator to recovery tank hose could be the cause. Who is correct?
Both A and B
Dye leak detectors are being discussed. Technician A says injection dye may be visible after a few days of system operation if a leak is present. Technician B says a special lamp is required to locate a small leak with fluorescent dye. Who is correct?
Both A and B
Reciprocating compressors are being discussed. Technician A says that the suction valve is opened to allow refrigerant vapor to enter due to a differential in pressure above and below the valve. Technician B says that the discharge valve is opened to allow refrigerant vapor to leave due to a differential in pressure above and below the valve. Who is correct?
Both A and B
Refrigerant analyzers or identifiers are being discussed. Technician A says if the analyzer displays "R-134a," then the refrigerant is 98 percent pure. Technician B says if "HC" is displayed, then the refrigerant is flammable. Who is correct?
Both A and B
Technician A says UV radiation inhibits the human body's immune system and causes skin tissue damage. Technician B says the release of CFCs into the atmosphere could help increase the greenhouse effect. Who is correct?
Both A and B
Technician A says a block or ladder diagrams are used to aid in troubleshooting air-conditioning duct system faults. Technician B says the use of test lights is not recommended for under dash service. Who is correct?
Both A and B
Technician A says a defective radiator cap vacuum valve may cause hoses to collapse. Technician B says a defective pressure valve may cause coolant boil over and loss. Who is correct?
Both A and B
Technician A says in an H-block valve the temperature sensing sleeve (bulb) is internally located in the outlet port of the valve. Technician B says the operation and function of the H-valve, or block valve, are essentially the same as the thermostatic expansion valve (TXV). Who is correct?
Both A and B
Technician A says latent heat cannot be felt. Technician B says latent heat cannot be measured with a thermometer. Who is correct?
Both A and B
Technician A says latent heat is hidden heat. Technician B says latent heat is required for a change of state. Who is correct?
Both A and B
Technician A says some coolants are ethylene glycol. Technician B says some coolants are propylene glycol. Who is correct?
Both A and B
Technician A says that serpentine belts made of EPDM resist cracking and instead exhibit wear to the belt ribs similar to tire wear and that a depth gauge should be used to assess belt wear. Technician B says that as a neoprene serpentine belt ages and wears that cracks will form on the belt ribs and that if there are more than 3 cracks in a 3 inch span the belt should be replaced. Who is correct?
Both A and B
Technician A says that the seal cavity may be flushed with clean refrigeration oil. Technician B says that the seal cavity may be flushed with clean mineral spirits. Both agree that the residue must be disposed of in a proper manner. Who is correct?
Both A and B
Technician A says the air conditioning system is designed to remove heat from the passenger compartment. Technician B says the air conditioning system is designed to transfer heat absorbed to the outside air. Who is correct?
Both A and B
Technician A says the compressor is the dividing line of the refrigeration system, low- to high-side. Technician B says the metering device is the dividing line of the refrigeration system, high- to low-side. Who is correct?
Both A and B
Technician A says there is a direct relationship between the pressure and temperature of a refrigerant. Technician B says pure refrigerant temperature-pressure relationships in a contaminated system are not valid. Who is correct?
Both A and B
Technician A says when a musty odor develops the odor causing mold and mildew must be eradicated. Technician B says that a liquid antimicrobial ¬deodorizer and disinfectant is used to eliminate odors in duct systems. Who is correct?
Both A and B
The Clean Air Act is being discussed. Technician A says the Montreal Protocol is one of the results of the Clean Air Act. Technician B says it gave the EPA authority to control refrigerants in order to protect the environment. Who is correct?
Both A and B
The function of a scroll compressor is being discussed. Technician A says that its function is to create a low pressure condition in the system. Technician B says that its function is to increase the temperature and pressure of refrigerant vapor. Who is correct?
Both A and B
The methods used to drive a compressor are being discussed: Technician A says that automotive air-conditioner compressors have an electromagnetic clutch. Technician B says that a serpentine belt system is often used to drive a compressor clutch. Who is correct?
Both A and B
There are signs of oil spray on the compressor clutch hub and nearby underhood areas. Technician A says that a leaking compressor shaft seal could be the cause. Technician B says that a faulty compressor clutch bearing could be the cause. Who is correct?
Both A and B
technician A says that the A/C system may be charge through the LOW side when the system is operating. Technician B says that the A/C system may be charged through the HIGH side when the system is off. Who is correct?
Both A and B
During the compression stroke of an air-conditioning compressor, the suction valve is closed by the:
Discharge pressure
All of the following statements about the air conditioning circuit are true, EXCEPT:
Heat transfer is accomplished by two pressure and two temperature systems
How is heat transfer by convection accomplished?
Heat travels through the surrounding air.
An air-conditioning compressor clutch failed due to overheating. What is the most likely cause of the failure?
High resistance in the compressor
A slipping compressor clutch may be due to all of the following, except:
Low refrigerant charge
What could happen if the evaporator pressure becomes too low?
Moisture will freeze on the evaporator surface restricting air flow.
Most original equipment manufacturers use what type of lubricant in their R-134a systems?
PAG
After a vehicle has been driven for 10-15 miles, the heater still continues to blow cool air. Which of the following is the most likely cause?
Partially blocked heater core
Most air-conditioning systems that have R-134a as the refrigerant also use _______________ as a lubricant
Polyalkaline glycol (PAG)
Once the refrigerant from the air conditioning system has been recovered, which of the following should the technician do?
Record the amount of refrigerant oil removed from the system.
The angle of the swash plate in a variable displacement compressor is controlled by:
Suction pressure differential in the crankcase
Charging the system is being discussed. Technician A says the refrigerant must be weighed (or metered) to obtain a proper charge. Technician B says overcharging the system will reduce its cooling efficiency. Who is correct?
Tech B only
On a refrigerant system there is heavy frost on the expansion valve inlet and low-side pressure is well below normal. Technician A says that the expansion valve stuck in the open position could be the cause. Technician B says that a restricted expansion valve inlet screen could be the cause. Who is correct?
Tech B only
Technician A says you should always disconnect the power source while working on electric cooling fan motors. Technician B says it is safe to work on electric cooling fan motors when the ignition switch is off. Who is correct?
Technician A only
Hydrostatic pressure is being discussed. Technician A says the pressure in a tank will increase as the liquid cools. Technician B says the containment system (tanks and lines) must withstand the changing pressures created as the liquid changes states. Who is correct?
Technician B only
Performance testing on air conditioning is being discussed. Technician A says the engine should be operated at speeds over 3,000 rpm during the test. Technician B says a fan should be used to force air through the condenser and radiator. Who is correct?
Technician B only
Technician A says a receiver-drier is used in systems with a fixed orifice tube. Technician B says the receiver-drier stores reserve refrigerant. Who is correct?
Technician B only
Technician A says that the evacuation process will remove dirt and debris from the refrigerant system. Technician B says that the evacuation process will remove moisture and air from the refrigerant system. Who is correct?
Technician B only
Technician A says the amount of refrigerant flowing through an orifice tube is controlled by a remote sensing bulb. Technician B says the orifice tube is located in the liquid line between the condenser outlet and evaporator inlet. Who is correct?
Technician B only
All of the following statements about variable displacement compressors are true, except:
Variable displacement compressors have a cycling clutch.
While a technician is performing an A/C system performance test, it is determined that the low pressure gauge is reading in the vacuum range. This reading could be caused by:
a restricted expansion valve
Sensible heat can be measured with
a thermometer.
The temperature of superheated refrigerant is
above its boiling point
ank pressure is high and contaminated with non-condensable gas.
accumulator.
O-ring damage could be caused by
all of the above
During routine equipment inspection a technician notices that the R-134a recovery tank pressure is 115 psig at an ambient tank temperature of 85°F. Using the chart below what should the technician conclude?
ank pressure is high and contaminated with non-condensable gas.
An inoperative cooling fan may cause high lead (high-side) pressure at what vehicle speeds?
both A and B
Which of the following could cause very low pressures on the low side of a system equipped with an expansion valve?
expansion valve stuck closed
Where in the system is the receiver dryer located?
on the outlet of the condenser.
An engine coolant temperature switch or sensor is used to directly or indirectly energize the:
radiator fan motor relay.
The compressor pumps refrigerant as a
vapor
The following are automotive air-conditioning system compressor types, except
Centrifugal
