AC final
All of the following could reduce electrical circuit current flow except:
A Power wire that is shorted to a ground path
The shims shown in the illustration are used to: (see Image)
Adjust the air gap
An odor from the evaporator may be caused by all of the following, except:
All of the above
If the crankshaft pulley turns clockwise (cw), all of the following statements about the illustration below are true, except: (look at image)
The water pump turns clockwise
All of the following statements about injecting a dye solution into the air-conditioning system are true, except:
They dye affects the overall performance of the system
All of the following statements about engine cooling systems are true EXCEPT:
b. It is ok for a technician to install a thermostat with a low temperature rating than the original thermostat.
All of the following are processes by which heat moves, except:
b. Latent
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. A only
Vacuum pump efficiency is being discussed.Technician A says that vacuum pump efficiency is greatest at sea level.Technician B says that altitude has little or no effect on vacuum pump efficiency.Who is correct?
a. A only
What is the state of the refrigerant in line 4?Technician A says that it is high-pressure vapor.Technician B says that it is high-pressure liquid.Who is correct? (see image below)
a. A only
Check My Work A photodiodes can be used to detect minute amounts of:
a. Light
Voltage is defined as electrical pressure and is measured in:
a. Volts
A relay is an electromagnetic switch that allows a small amount of current to control:
b. A large current
If a thermostat fails in the open position, all of the following will occur, except:
b. A loss of engine coolant.
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?
b. A misadjusted front blend door
Check My Work Technician A says that the component identified by A is a receiver-drier.Technician B says that the component identified by D is a condenser.Who is correct? (see image)
b. B only
What component is shown as C?Technician A says that it is an accumulator.Technician B says that it is a receiver-drier.Who is correct? (see image below)
b. B only
What is the purpose of the desiccant?Technician A says it is to clean the refrigerant.Technician B says it is to dry the refrigerant.Who is correct?
b. B only
What type of heat transfer requires air movement?
b. Convection
Ohm's law defines the relationship between all of the following except:
b. Corrosion
The blower motor in the figure below has blower motor speeds M2, M3, and High, but does not run in either LOW or M1. Which of the faults listed below could be the cause? (see image)
b. Faulty resistor block
Check My Work The concern in the world community has shifted from the threat of ozone-depleting chemicals to a concern over which of the following?
b. Global warming
A vehicle is driven for 15-20 miles and the vehicle's passenger compartment blower motor continues to blow cold air. What is the most likely cause of this condition?
b. Partially restricted heater core
The electronic variable displacement compressor is based on what type of compressor design?
b. Swash plate compressor design
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?
b. The resistor block assembly is faulty.
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?
b. The system is functioning normally.
All of the following are the function of the radiator pressure cap except:
b. To lower the freeze point of the coolant.
When the cooling system is placed under pressure, for each pound per square inch (psi) of cooling system pressure, the boiling point of the coolant is increased by:
c. 3°F
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?
c. A dirty cabin air filter
The metering device changes high-pressure liquid to:
c. A low-pressure liquid
During a system performance test, the low-side gauge reading and the high-side gauge reading are about the same. Which of the following is the most likely cause?
c. A malfunctioning compressor
Current is defined as the flow of electrons and is measured in:
c. Amperes
Fluorescent leak detector scanner solution is being discussed:Technician A says once introduced into the system, it cannot be removed.Technician B says a ultraviolet light is required for detecting a leak. Who is correct?
c. 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?
c. Both A and B
Technician A says that O-rings designated for R-12 service need not 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?
c. Both A and B
Technician A says that a sight glass is often found in an R-12 system.Technician B says that a sight glass is seldom found in an R-134a system.Who is correct?
c. Both A and B
Technician A says that service ports may be a source of leaks.Technician B says that hose connections are sometimes a source of leaks.Who is correct?
c. Both A and B
During a system performance test, the low-side gauge is reading a vacuum. Which of the following is the most likely cause?
d. A restricted expansion valve
Technician A says that the line or hose that connects the compressor outlet to the condenser inlet is called the discharge line.Technician B says that the line or hose that connects the evaporator outlet to the compressor inlet of a TXV system is called a suction line.Who is correct?
c. Both A and B
Technician A says the compressor is one of the points in the air-conditioning system where there is a separation between a high and a low pressure.Technician B says the metering device is one of the points in the air-conditioning system where there is a separation between a high and a low pressure. Who is correct?
c. Both A and B
What is the state of the refrigerant in line 5?Technician A says that it is low pressure.Technician B says that it is a vapor.Who is correct? (see image)
c. Both A and B
All of the following are true of voltage drops except:
c. Corrosion in a circuit does not cause a voltage drop.
During a refrigerant system performance test the following results are recorded: outside ambient temperature of 90°F, high-side gauge reading of 145 psi, and low pressure gauge reading of 14 psi. What is indicated by these results?
c. Low refrigerant levels
Engine coolant is designed to provide all of the following except:
c. Lower the boiling point of the solution.
The following may be used to maintain in-vehicle temperature, except:
c. Mass airflow sensor
An inoperative vacuum motor could be caused by all of the following, except:
c. Mode door cable misadjustment
When the air-conditioning system is first turned on, a musty odor comes from the vents. What is the most likely cause for this?
c. Mold formation on the evaporator core
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?
c. Refer to the appropriate diagnostic fault chart.
A customer complains of poor air-conditioning cooling performance. During a system performance test, the low-side gauge reading is 50 psig; the high-side gauge reading is 310 psig; and the ambient air temperature is 81°F (27.22°C). What is the least likely cause of the above results?
c. Refrigerant undercharge
A refrigerant retrofit label must contain all of the following except:
c. The amount of R-12 removed from the system
All of the following are common circuit faults except:
c. Voltage drop test.
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?
d. A compressor clutch relay is stuck in the closed position.
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?
d. A disconnected in-car temperature sensor aspirator tube
In a normally operating system, the refrigerant is in different physical states (vapor or liquid) at the various sections of the system. All of the following are physical states the refrigerant would be found in at various specific locations except:
d. A high-pressure liquid at the condenser
All of the follow are true about engine thermostats except:
d. A thermostat may be removed from a system if it is running hot.
Refrigerant system air contamination may be caused by:
d. All of the above
An R-134a thermal expansion valve system contains the proper refrigerant charge. During a system performance test, the low-side gauge reading is 40 psig and the high-side gauge reading is 140 psig with an ambient air temperature of 87°F (30.55°C). Which of the following is the most likely cause of these results?
d. An expansion valve stuck open
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?
d. Compressor clutch air gap too large
During normal air-conditioning system operation, the position of the system mode doors:
d. Depends on the mode selected.
Technician A says the fixed orifice tube can vary the amount of refrigerant allowed to flow to the evaporator.Technician B says the thermostatic expansion valve has a fixed opening and cannot vary the amount of refrigerant allowed to flow to the evaporator.Who is correct?
d. Neither A nor B
Resistance is defined as the opposition to current flow and is measured in:
d. Ohm's
All of the following are forms of heat transfer that take place as it relates to the vehicle air-conditioning system except:
d. Perspiration
In the case and duct system the air distribution mode doors may be operated by all of the following except:
d. Potentiometers
The following statements about a typical system set to MAX cooling are true, except:
d. Return air is from vehicle exterior.
Moisture removal from a refrigerant system is being discussed. The length of system evacuation time required depends on all of the major factors listed below except:
d. The amount of oil in the system
Air in the cooling system can cause all of the following except:
d. The coolant hoses bursting due to air pressure
Under normal operating conditions all of the following occurs inside the evaporator, except:
d. The refrigerant changes from a vapor to a liquid
The compressor pumps refrigerant as a:
d. vapor
It is necessary to drain the engine coolant before replacing which component?
the heater core
The blower motor does not operate, although there are 12 volts available at motor terminal "A" in the illustration. The most likely problem is: (Look at image)
Loose or defective motor ground wire
The least likely problem associated with a cooling system that had the thermostat removed is:
Loss of coolant
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 term "purge an air-conditioning system" in general terms means to:
Remove the refrigerant from the system
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.
Check My Work Electric cooling fans are being discussed:Technician A says that they are independent of the ignition switch and may start and run without notice at any time.Technician B says that they are generally protected by a shroud and pose no safety problem.Who is correct?
A. A only
Technician A says that a change in temperature from the inlet to the outlet of the thermostatic expansion valve (TXV) is not acceptable.Technician B says that a change in temperature from the inlet to the outlet of a fixed orifice tube (FOT) is acceptable.Who is correct?
B only
Engine overcooling is being discussed:Technician A says that a thermostat stuck open could be the cause of this condition.Technician B says that a missing thermostat could be the cause of this condition.Who is correct?
C. Both A and B
Technician A says that when pressure testing a cooling system, it should hold pressure for 5 minutes.Technician B says that a wet carpet may indicate a heater core leak.Who is correct?
C. Both A and B
What is the main source of ozone-depleting chlorine in the stratosphere?
C. Chlorine contained in chlorofluorocarbons
Technician A says that all orifice tubes are the same size, but they are not interchangeable.Technician B says that all orifice tubes are not the same size, but they are interchangeable.Who is correct?
A only
Technician A says that fluorescent tracer dye is easily detected using an ultraviolet lamp.Technician B says that the dye should be removed from the system after leak detection.Who is correct?
A only
Technician A says that a vacuum pump is used to remove moisture from a system.Technician B says that an air pump is used to remove air from a system.Who is correct?
A. A only
Each type of refrigerant uses a unique set of service fittings that:
Are designed to prevent accidental mixing of refrigerant
Technician A says that the performance test determines if system pressures are proper.Technician B says that the test determines if the system temperatures are proper.Who is correct?
Both A and B
When an air-conditioning system is opened for repairs or service, there is a possibility that __________ will enter system.
Both A and B
The following statements regarding a visual inspection for intermittent faults are all true, except:
Inspect for catastrophic component failure.
Technician A says that if the orifice tube is missing, the low-side pressure will be low.Technician B says that if the orifice tube is plugged with debris, low-side pressure will be high.Who is correct?
Neither A nor B
The purpose of the compressor is to:
Pump low-pressure vapor to a high-pressure vapor
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
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
The illustration below shows: (see image below)
neither A nor B
An odor emitting from the case and duct system may be caused by all of the following, except:
refrigerant gas leak
During initial system evaluation an unknown refrigerant is identified. Which of the following should a technician do?
treat it as a contaminated refrigerant
Technician A says that a manifold and gauge set is one of the primary service tools for the air-conditioning service technician.Technician B says that a manifold and gauge set must be dedicated to the type of refrigerant being serviced.Who is correct?
Both A and B
Technician A says a circuit has an open when there is a complete path for current to flow.Technician B says that an open circuit will not cause a circuit protection device such as a fuse to fail.Who is correct?
B. B only
A leaking evaporator is being replaced on a vehicle.Technician A says that some additional refrigerant oil should be added to the air-conditioning system prior to recharging it.Technician B says that the new O-rings or seals should be coated with clean refrigerant oil.Who is correct?
Both A and B
Check My Work Technician A says that a standing vacuum test may be held to check an air-conditioning system for leaks.Technician B says that a standing vacuum test does not reveal how many leaks there are in the system.Who is correct?
Both A and B
Check My Work Technician A says that the air-conditioning system can be charged from the low side while the system is running.Technician B says that the air-conditioning system can be charged from the high side while the system is not running.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
The blower motor does not operate. The voltage at point F on the illustration is 0 volts. The most likely cause of this problem is a defective:
10-ampere fuse
After a repair that required opening the refrigerant system the system should be evacuated (pumped down) for a minimum of how many minutes?
30 Minutes
If a poor electrical connection is suspected, which is the most effective test to perform?
A voltage drop test at the connector
Before installation:Technician A says refrigerant system O-rings can be coated with a gasket sealant.Technician B says that refrigerant system O-rings should be coated with new refrigerant oil.Who is correct?
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?
B only
Technician A says that when testing for a refrigerant leak, the electronic leak detector probe should be held against the suspected leak area.Technician B says that the electronic leak detector requires routine calibration and probe tip maintenance.Who is correct?
B only
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
The tank on a radiator has ruptured:Technician A says that a thermostat that is stuck in the open position could be the cause.Technician B says that a faulty radiator cap could be the cause.Who is correct?
B only
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 both hand valves must be closed to read service pressures.Technician B says there is a common passage on a manifold and gauge set.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.Who is correct?
Both A and B
Technician A says that a system is contaminated if it contains more than 2 percent of a foreign substance.Technician B says that air is considered a contaminant if it exceeds 2 percent of the system capacity.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
Technician A says that desiccant is found in the receiver-drier.Technician B says that desiccant is found in the accumulator.Who is correct?
Both A and B
Cooling system service is being discussed:Technician A says that ethylene glycol antifreeze must be disposed of in a manner prescribed by the Environmental Protection Agency (EPA) and local ordinances.Technician B says that after hoses have been replaced, clamp tension should be rechecked after the cooling system has been allowed to thermocycle.Who is correct?
C. Both A and B
Technician A says that chlorine (Cl), an ingredient of CFC refrigerants, is harming the ozone layer. Technician B says that the ozone layer is important for protection from ultraviolet (UV) radiation. Who is correct?
C. Both A and B
Before attempting to service an automotive air-conditioning system consider all of the following except:
Can customer afford the repair?
An overheating condition is being discussed:Technician A says that replacing the thermostat with one of a lower temperature rating will reduce the coolant temperature.Technician B says that replacing the pressure cap with one of a lower rating will reduce the coolant temperature.
D. Neither A nor B
Coolant loss is being discussed:Technician A says that a missing thermostat could be the problem. Technician B says a heater control valve stuck open may be the problem.Who is correct?
D. Neither A nor B
Technician A says that an R-12 manifold and gauge set may be used on an R-134a system.Technician B says that an R-134a manifold and gauge set may be used on an R-12 system.Who is correct?
D. Nether A nor B
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
During the compression stroke of an air-conditioning compressor, the suction valve is closed by the:
Discharge pressure
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 could cause very low pressures on the low side of a system equipped with an expansion valve?
Expansion valve stuck closed
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
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 fixed orifice tubes are interchangeable in order to tailor system performance.Technician B says that fixed orifice tubes may be located anywhere between the evaporator outlet and the compressor inlet.Who is correct?
Neither A nor B
Technician A says that the low-side gauge may be used on the high side, if necessary.Technician B says that the high-side gauge may be used on the low side, if necessary.Who is correct?
Neither A nor B
Technician A says that the minimum flow test on a TXV is made by wrapping the remote bulb in a warm rag.Technician B says that a maximum flow test may be made on a TXV by immersing the remote bulb in ice water (H2O). Who is correct?
Neither A nor B
An R-134a system has both excessively high low-side and high-side system pressures. Which of the following is the most likely cause?
The refrigerant system is overcharged
Technician A says if a wire or wiring in a circuit has higher than designed resistance, the wire will drop some of the available voltage.Technician B says unwanted resistance will cause current flow to go up in a circuit and the circuit protective fuse will fail.Who is correct?
a. A only
Most vendors will not honor the warranty on a new or rebuilt compressor if the _______________ is not also replaced at the time of service.
accumulator or receiver-drier
The following statements regarding the relationships between the cooling system and air-conditioning system are all true, except:
b. Ambient air first passes through the radiator, then the condenser.
Technician A says the wire harness, terminals, and connectors of the high-voltage system are identified by red.Technician B says to remove the service plug prior to disconnecting or reconnecting any HV connections or components.Who is correct?
b. B only
Heat transfer is being discussed:Technician A says that heat flows from a hot surface to a surface containing less heat.Technician B says that heat leaves the body by the process of evaporation.Who is correct?
c. Both A and B
Technician A says a voltage drop is the amount of electrical energy that is converted to another form of energy.Technician B says a voltage drop test is the preferred method of testing for unwanted resistance in a circuit when the circuit is under a load (turned on).Who is correct?
c. Both A and B
Technician A says to determine the type of refrigerant used in a system, a refrigerant identifier should be used prior to servicing the vehicle's refrigerant system.Technician B says that when working on a refrigerant system you should work in a well ventilated area.Who is correct?
c. Both A and B
All of the following are factors that affect body comfort except:
c. Concentration
The service valve adapter shown below is turned in the _______________ direction to allow access to the air-conditioning system. (look at image)
clockwise
All of the following may cause a low-pressure gauge to go into a vacuum, except:
clogged screen in the receiver-drier
If the compressor oil has been drained and it shows signs of metallic particles, all of the following should be done, except:
d. A full charge of heavier refrigeration oil should be added after flushing.
All of the following conditions could cause poor passenger compartment heating system performance except:
d. A thermostat stuck in the closed position.
Air conditioning is the process by which air is:
d. All of the above
The equipment shown in the illustration may be used to: (look at image)
d. All of the above
What is a material called that can block the flow of heat?
d. An insulator
What can ultraviolet radiation cause?
d. Both A and B
All of the following statements are true concerning high-voltage system safety, EXCEPT:
d. Disconnect the motor generators prior to turning the ignition off.
A refrigerant identifier will do all of the following except:
d. Display the percentage of water vapor (H2O)
All of the following are removed from an air-conditioning system during evacuation, except:
d. Lubricant
Technician A says the low-side gauge on the manifold gauge set is on the left and has a green housing.Technician B says the high-side gauge on the manifold gauge set is on the left and has a red housing.Who is correct?
d. Neither A nor B
Which of the following refrigerants may be vented?
d. Neither A nor B
Which of the following is not a tool used by the air-conditioning system technician?
d. OBD-5 scanner
The diode shown in the illustration is used to: (see image below)
d. Prevent voltage spikes in the electrical system
The most likely use for an engine coolant temperature switch is to electrically energize the:
Cooling system fan motor
A technician is diagnosing a system with a poor cooling complaint and both the high-side and low-side pressure readings are much higher than normal.Technician A says that this could be the result of leaves or debris blocking air flow through the condenser.Technician B says that the vehicle's air-conditioning system may be undercharged.Who is correct?
A only
Technician A says that a manifold and gauge set must have service shut-off valves within 1 ft. (30 cm) of the hose service end.Technician B says that a recovery/recycling station must have service shut-off valves within 1 ft. (30 cm) of the hose service end.Who is correct?
Both A and B
Technician A says that humidity has an effect on system performance.Technician B says that poor airflow has an effect on system performance.Who is correct?
Both A and B
Technician A says that moisture in the system can cause poor or no cooling.Technician B says that moisture in the system can cause harmful acids.Who is correct?
Both A and B
A slipping compressor clutch may be due to all of the following, except:
Low Refrigerant charge
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
Most air-conditioning systems that have R-134a as the refrigerant also use _______________ as a lubricant.
Polyalkaline glycol
After the refrigerant has been recovered from an air-conditioning system, which of the following should a technician do?
Record the amount of refrigerant oil removed from the system
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
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