Ch54/55 Test
The high pressure cutout switch disengages the compressor clutch when high-side pressure reaches _____ psi.
350 to 400
The filling level of a refrigerant container should never exceed _____ percent of the container's gross weight rating.
60
Technician A says a CCOT system has an expansion valve and a sight glass. Technician B says a CCOT system has an accumulator. Who is correct?
B only
Which of the following statements best defines the term "evacuation"?
Evacuation is a process that removes all traces of air, moisture, and refrigerant from the system
A liquid will boil at a lower temperature when it is put under pressure.
False
A problem with the HVAC mode control linkage, doors, or motor circuit cannot set a DTC.
False
A thermostatic expansion valve is mounted on the outlet side of the evaporator.
False
Which of the following statements is correct? Refrigerant leaves the compressor as a high-pressure, high-temperature liquid Refrigerant leaves the condenser as a low-pressure, high-temperature liquid Refrigerant returns to the compressor as a low-pressure, high-temperature vapor
None of these answers is correct
Which of the following oils can be used in an R-134a system?
PAG oil
Which of the following statements is NOT correct?
The evaporator changes heated refrigerant to a liquid
Which of the following statements is NOT true about orifice tube systems?
The liquid line from the condenser outlet to the orifice tube should be cool
A malfunctioning engine thermostat can be the cause of poor heater performance.
True
Frost on the outside of the receiver/dryer, but not on the liquid line between the condenser and receiver/dryer indicates ______.
a restriction in the receiver/dryer
A manifold gauge set can be used during A/C system diagnosis.
True
Some cabin air filter elements are impregnated with baking soda and a filter with a biocidal cartridge. Both prevent the growth of bacteria, mold, mildew, algae, and yeast.
True
The heater control valve is often called the water flow valve.
True
The heater core may be plugged if the inlet hose feels hot and the outlet hose feels cool.
True
The high-voltage electrical system of a hybrid vehicle should be shut down and isolated from the vehicle prior to working on the A/C compressor.
True
Technician A says the thermostatic expansion valve and the fixed orifice tube perform the same function. Technician B says heat from the evaporator core surface is lost to the boiling and vaporizing refrigerant. Who is correct?
both A and B
Technician A says there should be a gradual change from hot to warm as you move your hand along the return bends of the condenser from the bottom to the top. Technician B says a restriction in the condenser will be evident by a sudden change in temperature. Who is correct?
both A and B
The blower motor does not run in any fan switch position. A check with a DMM reveals that power is getting to the motor. Technician A says the motor ground is bad. Technician B says the motor is burned out. Who is correct?
both A and B
Heater control valves are operated by a ______.
cable Electric motor vacuum motor
Technician A says refrigerant leaves the compressor as a high-pressure liquid. Technician B says the condenser changes the high-pressure liquid refrigerant into a high-pressure vapor. Who is correct?
neither A nor B
A heating system includes all the following parts EXCEPT:
receiver/dryer
Large amounts of black dust around the clutch plate is an indication of _____.
slipping A/C belt
The largest and coolest line/hose in the A/C system is the ______ line.
suction
The boiling point of a liquid increases as ______.
the pressure applied to it increases
The evaporator is located _____.
under the dash
A vehicle is being diagnosed for poor A/C performance. The engine is started, and when the system is set to MAX A/C, the compressor engages normally. When the temperature control knob is moved from hot to cool, only hot air blows out of the A/C outlets. Technician A says there is a problem with the air duct system or the controls. Technician B says the system is low on refrigerant. Who is correct?
A only
Technician A says European and Japanese manufacturers shipping vehicles to the US will eliminate R-134a A/C systems by 2017. Technician B says the United States will switch to R-22 in 2015. Who is correct?
A only
Technician A says R-12 is a chlorofluorocarbon (CFC) that damages Earth's ozone layer. Technician B says R-134a is a hydrofluorocarbon (HFC) that causes even greater damage. Who is correct?
A only
Technician A says hybrid vehicles use electrically driven high voltage A/C compressors. Technician B says the compressors for hybrids use the same refrigerant oil as regular vehicles. Who is correct?
A only
Technician A says in most cases, problems with the heating system are problems with the engine's cooling system. Technician B says a restricted heater return hose can cause excess heat in the passenger compartment. Who is correct?
A only
Technician A says the refrigerant oil container should not be opened until it is time to use it and should be capped immediately after use. Technician B says after the system has been opened, compressed air should be used to flush dirt, moisture, and old refrigerant oil out of the system. Who is correct?
A only
Technician A uses the ohmmeter function of a DMM [digital multimeter] to test the resistor block for opens. Technician B tests the resistor block with a lab scope. Who is correct?
A only
Thermal expansion valves are being discussed. Technician A says the TEV regulates the refrigerant flow to the evaporator by balancing the inlet flow to the outlet temperature. Technician B says the TEV is closed when the temperature at the outlet of the evaporator is high. Who is correct?
A only
Technician A says a hybrid vehicle has a large reservoir of liquid refrigerant to keep the passenger compartment cool during long periods when the engine is shut down. Technician B says some hybrid vehicles have electrically driven A/C compressors. Who is correct?
B only
Technician A says the compressor can pump both liquids and vapor. Technician B says the compressor is driven off the crankshaft by a belt. Who is correct?
B only
Technician A says the oil level of the compressor should be checked every year. Technician B says the system should be charged only after it has been completely evacuated. Who is correct?
B only
Technician A says the presence of oil around a fitting of an air-conditioning line may indicate an oil leak but not a refrigerant leak. Technician B says using an electronic leak detector is the best way to find the source of a refrigerant leak. Who is correct?
B only
Technician A says the receiver/drier is located on the low [pressure] side of the A/C system. Technician B says the accumulator is located on the low side of the system. Who is correct?
B only
Technician A says when the pressure applied to a liquid is increased, the boiling point decreases. Technician B says when the pressure on a liquid is suddenly released, heat energy is absorbed into the liquid. Who is correct?
B only
The owner of a car complains of a whistle or hiss only after the engine is shut down and only when the air-conditioning has been running. Technician A says there is a broken or leaking vacuum hose inside the dash. Technician B says this is a normal noise caused by the pressure of the refrigerant equalizing after the engine is turned off. Who is correct?
B only
All new vehicles sold in the United States must have a cabin air filter or a slot where one can be installed.
False
High relative humidity is more comfortable than low humidity.
False
In an R-134a system, pressure and performance testing are the only ways to identify low refrigerant levels.
False
PAG oil works well with R-12 refrigerant.
False
Refrigerant is a low-pressure liquid as it leaves the condenser.
False
Temperature/pressure charts are not required when manifold gauges are used in A/C performance testing.
False
Which of the following statements concerning evaporators is NOT true?
High-pressure vapor leaves the evaporator at the top
Before 1994, most manufacturers used _____ as a refrigerant.
R-12
Which of the following statements is not correct?
The accumulator is located between the condenser and the receiver/dryer
A manifold gauge set can be used during the evacuation of the A/C system.
True
A manifold gauge set is used to determine both high-side and low-side pressures in the refrigeration system.
True
According to Section 609 of the Federal Clean Air Act, no one repairing or servicing a motorvehicle's A/C system can do so unless that person is properly trained and certified.
True
Aluminum tubing is often used to connect air-conditioning components where flexibility is not required.
True
Most current HVAC systems use electric servomotors to move the various doors.
True
Most vehicles have a cabin filtration system that cleans the air before it enters the passenger compartment.
True
R-134a is a hydrofluorocarbon.
True
Section 609 of the U.S. Clean Air Act of 1990 requires that all service technicians who work on A/C systems must be certified in proper refrigerant recovery and recycling.
True
Which of the following cannot cause excessive heat?
a water flow control valve not opening fully
A loud squealing noise could be caused by ______.
a worn compressor clutch oil on the compressor clutch a seized compressor
The purpose of the desiccant bag in a receiver/drier or accumulator is to ______.
absorb moisture inside the system
Which of the following may be electrically connected in series with the compressor electromagnetic clutch?
all answers are correct
A subcooler is located ______.
at the bottom of the condenser
Variable displacement compressors are normally _____ compressors with a pivoting wobble plate.
axial
EPA certification is required to _____.
both "service R-12 A/C systems" and "purchase R-12"
A poor heat out of the floor duct condition is being discussed. Technician A says the coolant level in the engine's cooling system may be low. Technician B says the engine's thermostat may be faulty. Who is correct?
both A and B
A vehicle with insufficient heater performance is being discussed. Technician A says the problem could be a stuck-open engine thermostat. Technician B says air could be trapped inside the heater core. Who is correct?
both A and B
A/C parts replacement is being discussed. Technician A says if the system has been open for more than two minutes, the entire system must be completely evacuated and a new accumulator must be installed. Technician B says if the compressor has internal damage the condenser may need to be flushed and the receiver/dryer or accumulator replaced. Who is correct?
both A and B
Technician A says air in the system can cause excessive pressure within the A/C system. Technician B says moisture can cause freeze-up at the expansion valve. Who is correct?
both A and B
Technician A says an A/C system using CO2 [carbon dioxide] for a refrigerant will not contribute to global warming and is environmentally friendly. Technician B says CO2 refrigerant does not need to be recovered and recycled. Who is correct?
both A and B
Technician A says evacuating (pumping down) an air-conditioning system removes air and moisture from the system. Technician B says evacuating (pumping down) an air-conditioning system must be done anytime the system has been opened for repairs. Who is correct?
both A and B
Technician A says hybrid vehicles have an electric water pump to circulate coolant through the heater core when the engine is stopped. Technician B says hybrid vehicles have a hot coolant storage tank to provide heat for the passenger compartment when the engine is shut down. Who is correct?
both A and B
Technician A says if the suction line to the compressor is covered with thick frost, this might indicate that the expansion valve is flooding the evaporator. Technician B says the formation of frost on the outside of a line or component means there is a restriction to the flow of refrigerant. Who is correct?
both A and B
Technician A says pinhole leaks in the evaporator may be caused by acid formed when water and refrigerant are mixed. Technician B says leaks are most often found at hose connections and at the various fittings and joints in the system. Who is correct?
both A and B
Technician A says suction lines connect the accumulator to the compressor. Technician B says discharge lines connect the compressor to the condenser. Who is correct?
both A and B
Technician A says the cabin air filter should be replaced every 12,000 to 15,000 miles (19,300 to 24,140 km) or once a year. Technician B says some cabin air filters have a charcoal layer for odor absorption. Who is correct?
both A and B
Technician A says the magnetic clutch is usually pressure controlled, cycling the compressor on and off to regulate system temperature or pressure. Technician B says the clutch operates continually when the system is turned on. Who is correct?
both A and B
Technician A says the suction line connected to the compressor should be cool to the touch. Technician B says the discharge line from the compressor to the condenser should be hot along its entire length. Who is correct?
both A and B
When replacing a typical A/C system component, the system must be discharged _____.
completely
When is a manifold gauge set used?
discharging charging evacuating
The refrigerant is at its lowest pressure and temperature at the ______.
evaporator orifice [inlet]
Which of the following components is NOT part of a receiver/drier?
expansion valve
Heater cores with electric PTC heater strips are used on what type of vehicle?
hybrid vehicles
The manifold gauge set has an inches-of-mercury [vacuum] scale on the _____ gauge.
low-side
Technician A says the normal operating pressures of R-134a are slightly lower than the pressures of R-12. Technician B says R-134a boils at 134 degrees Fahrenheit. Who is correct?
neither A nor B
