ASE A7 Test Prep – Heating and A/C - Questions, Answers and Explanations Technician A says that the pressure cycling switch is usually located on the acc... [Show More] umulator. Technician B says that the refrigerant must be recovered from the system before the switch can be removed. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B The pressure cycling switch senses the low-side pressure near the evaporator outlet and is usually found on the accumulator. Technician B is wrong because the switch is often mounted on the Schrader fitting so it can be replaced without the loss of refrigerant. Technician A says that the A/C system can be charged through the high or low side only when the engine is not running. Technician B says that the A/C system can be charged though the low side when the engine is running. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B Charging the system can be performed through either the high side or low side when the engine is not running, but must be done only through the low side when the engine is running. This safety measure prevents high-side pressure from entering the refrigerant container and possibly causing an explosion. An air conditioning check has uncovered a discharge in the system and compressor damage. says Technician A that after the repairs are made, to check the low-pressure cutoff switch. Technician B says lubricating oil is carried by the refrigerant through the system. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B The purpose of the low-pressure cutoff switch is compressor protection. The compressor clutch circuit is opened if the pressure in the system drops too low. This would be an indication that the system had lost some or all of its refrigerant charge. Since the lubricating oil is carried by the refrigerant, a loss could cause damage to the compressor if it were allowed to operate without sufficient lubrication. When checking recycled refrigerant for excess non-condensable gases (air), Technician A says that the container must be stored at 65°F (18°'C) or above for 8 hours out of direct sunlight, before checking the pressure. Technician B says if the pressure is higher than the limit shown for a given temperature, there is air in the tank. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B To purge air, connect the tank to the recovery/recycling machine and slowly vent the air vapor from the top of the container. Continue venting until the pressure falls below the limit shown on your chart. If the pressure inside the container still exceeds the pressure limit shown, recycle the entire contents. Technician A is wrong because the container must be stored for 12 hours, not eight. The operation of the thermostatic switch depends on the temperature of the: A. condenser B. compressor C. evaporator D. outside air The thermostatic switch, which is used to cycle the A/C compressor on and off, depends on the temperature of the evaporator in order to operate. All of the following are causes for fan clutch re- placement EXCEPT: A. oil film on the back of the clutch B. no viscous drag C. fan speed does not increase as engine warms up D. when engine is hot, fan stops spinning in only two seconds after shut down A properly operating clutch should stop the fan from spinning within two seconds after a hot engine shit down. All of the other answers are indications of a defective fan clutch. Technician A says that an ambient temperature switch protects the compressor from damage. Technician B says that an ambient temperature sensor provides input for the Automatic Temperature Control (ATC) system. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B In non-ATC systems, the function of the ambient temperature switch is to inhibit compressor clutch operation in cold ambient temperatures. This function mainly protects the compressor from poor or no lubrication, which could be the result of cold refrigerant oil. In ATC systems, the ambient temperature sensor senses ambient outside temperature. As ambient or interior temperatures stray, the sensors pick up the change and the system adjusts the outlet duct temperature accordingly to compensate for the temperature changes. If a capillary tube were to break at some point between its sensing bulb and the expansion valve, what affect would it have on the valve? A. The expansion valve would stick open. B. The expansion valve would stick closed. C. The expansion valve would stick in whatever position it was in at the time of the break. D. There would be no affect on the expansion valve. Expansion valves are usually spring loaded devices with a diaphragm that is linked to a plunger. Without any pressure against the diaphragm from the gas in the capillary tube, the spring inside the expansion valve would cause the valve to stick closed. A customer has a complaint of poor heat output. After checking the hoses running from the heater core and finding them both to be hot, Technician A says the problem could be a clogged heater core. Technician B says a misadjusted temperature control cable could be the problem. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B If both hoses leading to the heater core are hot, coolant is circulating through the heater core. One hose that is significantly cooler than the other would indicate a clogged heater core. However, if the temperature control cable is incorrectly adjusted, the temperature blend door may not allow enough warm air to enter the passenger compartment for sufficient heating. During the diagnosis of an ATC system, a trouble code is obtained that references the blend door feedback sensor. Technician A says that the sensor should be replaced. Technician B says that the sensor circuit should be tested. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B Fault codes usually only indicate which circuit the problem is in; they don't necessarily indicate which component in the circuit has failed. The problem could be caused by a loose connection, improper modification, or a broken wire, so perform a thorough inspection when diagnosing a malfunction. Ensure that all grounds are clean and making gook contact. If basic mechanical and electrical checks fail to locate the [Show Less]
