section 2 CH 6, 7, 8
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?
both
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
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
During a refrigerant system performance test the following results are recorded: outside ambient temperature of 90 degrees F, high-side gauge reading of 145 psi, and low pressure gauge reading of 14 psi. What is indicated by these results?
. Low refrigerant levels
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
An R-134a thermal expansion valve system contains the proper refrigerant charge. During a system performance test, the low-side gauge reading and the high-side gauge reading are in the high range and the system has poor cooling performance. Which of the following is the most likely cause?
A restricted airflow across the condenser
During a system performance test, the low-side gauge is reading a vacuum. Which of the following is the most likely cause?
A restricted expansion valve
One of the functions of the air-conditioning compressor is to increase the pressure of the refrigerant. Another function of the compressor is to increase: A. The heat (temperature) of the refrigerant B. The volume of the refrigerant C. The vaporization point of the refrigerant D . Pump the liquid refrigerant
A. The heat (temperature) of the refrigerant
(picture) 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?
B Only
(picture) 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?
B only
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
Before attempting to service an automotive air-conditioning system consider all of the following except: A. Listen to customer complaint. B. Does your diagnosis make sense based on customer complaint? C. Can customer afford the repair? D. Do you have the proper tools and equipment to service the system?
C. Can customer afford the repair?
Temperature and pressure comparisons are a standard practice to determine all of the following, except: A. System change levels B. Superheat C. Subheat D. Subcooling
C. Subheat
Refrigerant system air contamination may be caused by: A. Refrigerant system low-side leak. B. Improper system evacuation or insufficient evacuation time. C. Weak evacuation pump. D. All of the above.
D. All of the above.
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: A. The amount of moisture in the system. B. The ambient temperature. C. The efficiency of the vacuum pump. D. The amount of oil in the system.
D. The amount of oil in the system.
To address the issue of small capacity refrigerant systems, the EPA adopted a new SAE standard effective December 2007, covering the accuracy level of future refrigerant recovery, recycling, and recharging equipment. The SAE number for this new standard is:
J2788
The high- and low-side pressures may be normal or slightly less than normal based on ambient air temperature. If the refrigerant system is not functioning as designed, the following items should be checked for proper operation:
Refrigerant system slightly undercharged
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 degrees F ( 27.22 degrees C). What is the least likely cause of the above results?
Refrigerant undercharge
The term "purge an air-conditioning system" in general terms means to: A. Remove the refrigerant from the system. B. Flush the refrigerant system. C. Recharge the refrigerant system. D. Add sealant to the refrigerant system.
Remove the refrigerant from the system.
The most accurate method for measuring the effectiveness of system evacuation is with the use of a:
Thermistor vacuum gauge.
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 degrees F ( 30.55 degrees C). Which of the following is the most likely cause of these results?
an expansion valve stuck open
Technician A says that if R-134a evaporating temperature is 30 degrees F ( -1.1 degrees C), the gauge pressure should be about 26 psig (179 kPa). Technician B says that a low-side gauge pressure of 26 psig (179 kPa) indicates a refrigerant evaporating temperature of in an R-12 system. Who is correct?
both
Technician A says that low suction and discharge pressure may indicate a low refrigerant charge. Technician B says that low suction and discharge pressure may indicate a restriction in the system. Who is correct?
both
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
Technician A says that an overcharged system will result in lower than normal low-side pressures. Technician B says that an overcharged system will result in a slight increase in cooling capacity, but only under low load conditions. Who is correct?
neither
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 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?
tech A
Technician A says that air is a non-condensable gas. Technician B says that air collects in the evaporator during the OFF cycle of the air-conditioning system. Who is correct?
tech A
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?
tech A
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?
tech A
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?
tech B
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?
A malfunctioning compressor
(picture) Technician A says that the component identified by B is an evaporator. Technician B says that the component identified by A is a condenser. Who is correct? Correct!
A only
(picture) What is the state of the refrigerant as it immediately enters the evaporator, line 1? Technician A says it is all liquid with some flash gas. Technician B says it is all vapor. Who is correct?
A only
(picture) 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?
A only
An R134a recovery tank pressure is determined to be 115 psig at 85 degrees F. What does this temperature-pressure relationship indicate? A. The recovery tank is contaminated with moisture. B. The recovery tank is contaminated with air. C. The recovery tank is overcharged. D. The recovery tank is at normal operating pressure.
B. The recovery tank is contaminated with air.
(picture) Which of the following statements identifies the correct state and pressure of the refrigerant throughout the system? A. The refrigerant is low pressure at points 1, 2, and 3 in the system and high pressure at points 4, 5, and 6 in the system. B. The refrigerant is low pressure at points 1 and 5 in the system and high pressure at points 2, 3, 4, and 6 in the system. C. The refrigerant is high pressure at points 1, 2, and 3 in the system and low pressure at points 4, 5, and 6 in the system. D. The pressure varies from high pressure to low pressure throughout the system, depending on heat loads.
B. The refrigerant is low pressure at points 1 and 5 in the system and high pressure at points 2, 3, 4, and 6 in the system.
All of the following statements about injecting a dye solution into the air-conditioning system are true, except: A. Dye is approved for automotive air-conditioning system use. B. Dye is available in either yellow or red. C. A few days after injection, the dye will be visible at the point of the leak. D. The dye affects the overall performance of the system.
D. The dye affects the overall performance of the system.
During a refrigerant system performance test, the high-side pressure instantly goes over 370 psig when the compressor is engaged. Which of the following is the most likely cause?
an overcharged system
(picture) 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?
both
Technician A says that a gauge reading of 21 psig (145 kPa) corresponds to an R-12 evaporator temperature of about 20 degrees F ( -6.7 degrees C). Technician B says that a gauge reading of 21 psig (145 kPa) corresponds to an R-134a evaporator temperature of about 23.5 degrees F ( -4.7 degrees C). Who is correct?
both
Technician A says that a liquid line restriction has the same general symptoms as a suction line restriction. Technician B agrees, adding, "An undercharge of refrigerant also has the same symptoms." Who is correct?
both
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?
both
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
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
Technician A says that special electronic leak detectors are available that are used for halogen gases. Technician B says that there are electronic leak detectors available that will detect CFCs as well as HFCs. Who is correct?
both
Technician A says that the accumulator should be replaced if there is moisture in the system. Technician B says that the accumulator must be replaced if the fixed orifice tube (FOT) is replaced. Who is correct?
both
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
While discussing systems equipped with an IHX: Technician A says that the IHX systems can get an increase in pressure on the low side by preheating the refrigerant before entering the compressor. Technician B says that the IHX uses a tube in tube design that passes the high side tube (before the metering device) through a larger low side tube and can get a head start on cooling by transferring some of its heat thru conduction. Who is correct?
both
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
Technician A says that one need not evacuate the system if the "sweep and purge" method is used. Technician B says that one need not evacuate the system if it has been "opened" for less than 5 minutes. Who is correct?
neither
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
While discussing thermostatic expansion valves: Technician A says that the remote sensing bulb of an H-block TXV must be secured to the evaporator outlet tube with special insulating tape. Technician B says that TXV systems have an adjustment procedure to set the opening and closing of the valve that must be adjusted on replacement. Who is correct?
neither
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?
tech B
Technician A says that a restriction in the suction line will cause excessive high-side pressure. Technician B says that a restriction will result in a pressure change, usually marked by frost or ice. Who is correct?
tech B
Technician A says that it is permissible, according to the EPA, to release refrigerant from the hoses of a manifold and gauge set because it is such a small amount. Technician B says that, to minimize refrigerant loss, shut-off valves are required by the EPA within 12 in. (30 cm) of the service end of the manifold and gauge set hoses. Who is correct?
tech B
Technician A says that mineral oil may be used to lubricate O-rings used on an R-134a system. Technician B says that PAG lubricants may be used on O-rings for an R-134a system. Note: Refer to shaded box in left column of Page 192 of the shop manual. Who is correct?
tech B
Technician A says that the minimum pressure recommended for leak testing an R-12 system is 60 psig (414 kPa). Technician B says the minimum recommended pressure for leak testing an R-134a system is 50 psig (414 kPa). Who is correct?
tech B
Technician A says that tobacco smoke will not affect refrigerant leak detection. Technician B says that an electronic halogen leak detector is the best method of leak detection. Who is correct?
tech B