ASE A7 - Heating & A/C
Technician A says when there is a "U" DTC, it should be repaired before any further diagnostics can be performed. Technician B says "U" DTCs indicate there is nothing wrong with the A/C system. Who is correct? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is A. A "U" DTC indicates there is a problem with the present modules not being able to communicate with each other. It is likely that the module responsible for generating a DTC for the A/C problem can't report the problem until it is able to communicate on the network. Repair the "U" DTC first then rescan for any present DTCs.
All of the following could cause lower than normal high-side pressure EXCEPT: A. missing air dam B. low refrigerant charge C. worn compressor D. restricted orifice tube
The correct answer is A. A lower than normal refrigerant charge and excessive internal wear would both cause the compressor to develop less discharge pressure. A restricted orifice tune would cause refrigerant flow through the system to be slowed. When the refrigerant spends more time in the evaporator, it's temperature and pressure are slightly reduced. Aissing air dam would cause an air flow problem through the condenser and the radiator. This reduced air flow and possible engine overheating would both cause higher than normal high side pressure.
Technician A says that evacuating an A/C system will remove air and moisture from the system. Technician B says that evacuating an A/C system will remove dirt particles from the system. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is A. Evacuating an A/C system removes air and moisture from the system. The receiver/drier may contain a filter or strainer to catch and trap foreign particles and dirt, but this remains in the receiver/drier and is not removed during the evacuation procedure.
The floor inside a vehicle is wet and there is a slimy film on the windows. Technician A says the heater core is leaking. Technician B says the evaporator case drain plug is clogged. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is A. Flogged windows that smear when wiped and moisture on the passage floor are telltale signs of a leaking heater core. Technician B is incorrect because, while a clogged evaporator case drain could cause the case to fill up with moisture and spill out onto the floor, it would not cause a slimy film on the windows.
When pressure testing the cooling system on a late model gasoline engine vehicle, the pressure on the tester drops but no leaks can be found in the engine compartment. Technician A starts the engine and, seeing the pressure on the tester gauge increase, says that there is an internal leak, a blown head gasket. Technician B says that there cannot be an internal leak because the engine oil looks normal, not milky like it would be if coolant were present, and there is no white smoke coming from the exhaust pipe. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is A. If the engine is started while pressure testing a cooling system and the pressure immediately increases, there could be a head gasket leak, but not into the crankcase. The coolant may be going out the tailpipe, but since this is a late model gasoline engine vehicle and equipped with a catalytic converter, there is no white smoke from the exhaust because the converter super-heats the coolant into such a fine vapor that it is not noticeable.
When identifying an A/C system, Technician A says that an accumulator located between the evaporator and compressor is an indication that the system has an orifice tube. Technician B says that when the high-side service port fitting is smaller than the one on the low side, the system uses R134a refrigerant. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is A. Systems using an expansion valve have a receiver- drier between the valve and condenser, while orifice tube systems have an accumulator between the evaporator and compressor. Technician B is wrong because on R134a systems, the low-side service port is the smaller one.
A compressor clutch will not engage. All of the following could be the cause EXCEPT: A. a closed high-pressure cutout switch B. low refrigerant level C. an open ambient temperature switch D. faulty compressor clutch coil
The correct answer is A. The high-pressure cutout switch is normally closed. It opens the compressor clutch circuit when high-side pressures are excessive in order to protect the compressor. All of the other answers would cause the compressor clutch to not engage.
A customer complains that when parallel parking, his car repeatedly stalls, but only when the air conditioning is on. Technician A says that the power steering pressure switch is defective. Technician B says that there is a problem with the power steering pump. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is A. The power steering pressure switch is installed in the power steering system and report high pressure conditions causes by a load being placed on the engine by the power steering pump. The computer may decide to temporarily shut down the compressor to prevent engine stalling or low idle speed, or it could also raise idle speed through control of an idle speed control device. During parallel parking maneuvers, the steering wheel is most likely being moved to full lock at some point, increasing pressure. Technician A is right because, if this increased pressure is not being communicated to the computer by the switch, the A/C compressor will continue to run with its load on the engine or the idle speed will not be raised enough to keep the engine from stalling. Technician B is wrong because if the problem was with the power steering pump, the stalling would occur regardless of whether the A/C was on or not.
Technician A says that the pressure cycling switch is usually located on the accumulator. 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 correct answer is A. 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.
A blower motor only works on high speed. Which of the following causes is the most LIKELY? A. defective blower relay B. defective blower resistor C. defective blower switch D. blown fuse or tripped circuit breaker
The correct answer is B. Answer D is incorrect because if the blower furs was blown or circuit breaker tripped, the blower would not work at all. Answer A is incorrect because a blower relay is generally only used for the high blower speed and this is working. Answer C, the blower switch is a possible cause but the most likely cause for operation on only high speed is that a portion of the resistor assembly is burned out.
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.
The correct answer is B. 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.
Technician A says that he can safely remove a HV A/C compressor without following any of the published OEM HV safety guidelines. Technician B says that in order to safely remove and replace a HV compressor a technician will need basic hybrid safety training, proper safety equipment and tooling (including protective gloves and voltmeter rated for use on hybrid systems) and will need to adhere to published OEM service procedures. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B
The correct answer is B. Failure to follow hybrid safety procedures could result in personal injury or damage to expensive HV components. At a minimum, a technician will need to isolate the HV battery source while wearing protective rubber gloves rated "OO" (1000 volts) which in turn are protected by leather linesmen's gloves. A CAT III rated voltmeter may also be needed to safely check that any HV voltage remaining st the compressor connector has dissipated to a safe level.
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
The correct answer is 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 problem, follow manufacturers electronic system test procedures.
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
The correct answer is 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.
When troubleshooting an ATC system, the system responds when the ambient and in-vehicle temperature sensors are heated and cooled. However, there is no response when the sunload sensor is exposed to a light source. Technician A says that the problem is with the system's programmer. Technician B says that the problem is with the sunload sensor. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is B. If the system reacts with a change to one or two inputs but not the third, the problem is most likely confined to the single sensor or its circuit. But if no reaction is observed on any of the units, or only a partial reaction is seen, the problem is usually with the programmer.
When using an electronic refrigerant leak detector, all of the following should be observed EXCEPT: A. Leak detectors are very sensitive to many types of gases. If the area is contaminated with refrigerant or other gases, use a fan or compressed air to blow the excess refrigerant away. B. Pass the probe around the top of components and hoses as refrigerant is lighter than air and tends to rise. C. Don't move the probe faster than one inch per second. D. Never allow the probe to contact any surface, to prevent contamination of the sensing tip.
The correct answer is B. Make sure that you pass the probe around the bottom of the components and hoses as refrigerant is heavier than air and tends to settle.
Technician A says that any compressor that and not a HV uses a belt is a belt-driven compressor component. Technician B says that some hybrids use a combination belt/electric compressor. Who is correct? A. Technician A B. Technician B C. Both A and B D. Neither A or B
The correct answer is B. Many Honda models use a compressor that is both belt driven and electrically driven. The HV portion of the compressor is used to maintain occupant comfort when the engine goes into "Idle Stop" mode.
When diagnosing an ATC system, most of the system temperature sensors can be tested for: A. resistance and current flow B. resistance and voltage drop C. voltage drop and current flow D. current flow and continuity
The correct answer is B. Most temperature sensors can be tested for resistance and voltage drop. In general, the sensor should be replaced if its resistance is not within specification. Since a temperature sensors resistance varies with temperature, check the sensor voltage against temperature and compare to manufacturer specifications.
When replacing a blend door actuator, Technician A says that after installing the actuator, the control module will automatically know what the step the actuator is on and there is no need for calibration. Technician B says that after replacing the actuator, one procedure for recalibrating the control module would be to remove the fuse for the module for at least 60 seconds, then replace the fuse and perform an operational test of the system. Who is correct? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is B. On some Automatic A/C systems, the Body Control Module/HVAC module will automatically control the actuator and position it within limits for normal operation when the module is rest by removing its power for more than 60 seconds.
A vacuum door actuator is being tested. When vacuum is applied with a hand held vacuum pump, the door does not move and the reading on the vacuum gauge is zero. Technician A says that the door does not move because it is binding or obstructed. Technician B says that the door does not move because the actuator is defective. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is B. Regardless of what condition the door is in, the key here is that the gauge reading is zero, meaning there is a vacuum leak in the actuator.
Technician A says that a special tool is required to disconnect and connect spring lock fittings. Technician B says that when assembling new spring lock fittings, new O-rings lubricated with clean refrigerant oil should be used. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is B. Technician A is wrong because a special tool is only required to disconnect spring lock fittings.
The compressor in an A/C system does not run. When a jumper wire is used to connect the battery positive terminal to the power connector, the compressor clutch engages. Technician A says that the clutch coil is defective. Technician B says that the pressure cycling switch could be defective. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is B. Technician A is wrong because if the clutch coil was defective, the compressor clutch would not engage. Technician B is correct because, since the compressor clutch engages when 12 volts is directly applied, the problem is in the compressor control circuit, which includes the pressure cycling switch.
says Technician A that mineral deposits can restrict air flow through the radiator. Technician B that internal restrictions in the radiator can be says detected from the outside. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is B. Technician A is wrong because mineral deposits can restrict coolant flow inside the radiator, not air flow through the radiator. Look inside the radiator doe large amounts of mineral deposits at the ends of the core tubes. Technician B is right because an infrared surface thermometer can be used to scan the surface of the radiator. With the engine hot and idling, the radiator should be warmest bear the inlet and gradually cool toward the outlet. If there are areas that are considerably cooler than the inlet, then there may be restrictions at those areas.
At what percentage is refrigerant considered to be pure and safe for recovery? A. 90% B. 95% C. 98% D. 100%
The correct answer is C. Refrigerant is considered pure and safe for recovery if it is at least 98% by weight of a single type of refrigerant. If the refrigerant in the system is less than 98% pure, it should be considered contaminated and reclaimed or destroyed.
A vehicle with R134a refrigerant in the A/C system has a refrigerant leak. Technician A says that a propane gas leak detector should be used to find the location of the leak. Technician B says that an electronic leak detector should be used to check for leaks. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is B. Technician A is wrong because propane gas leak detectors cannot detect R134a. Technician B is right, but he must make sure the electronic leak detector is designed for R134a, as many older units are not.
The ambient temperature sensor in an EATC system is being tested. Technician A that says the resistance of the sensor should increase as it is heated. Technician B says that, as the sensor resistance changes, the computer reads the change in voltage drop across the sensor. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is B. The ambient temperature sensor is an NTC thermistor. When an NTC thermistor is heated, the resistance should decrease, and when it is cooled, resistance should increase.
There is a growling or rumbling noise at the AC compressor when the system is off and the engine is running. The noise stops when the system is turned on. Technician A says that a bad compressor bearing could be the cause. Technician B says that a bad compressor clutch bearing could be the cause. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is B. The compressor clutch bearing allows the rotor/pulley assembly to spin independently of the compressor shafts when the A/C system is off. When the engine is running and the A/C system is off, the compressor clutch bearing is spinning. When the A/C system is turned on, the rotor/pulley assembly and the armature are locked together by the magnetic action of the compressor clutch coil.
When recovering refrigerant from an a/c system, how long should the technician wait after the recovery/ recycling unit has been turned off to see if there is any residual pressure in the system? A. 1 minute B. 5 minutes C. 10 minutes D. 15 minutes
The correct answer is B. The technician should wait five minutes and watch the gauge to see if there is any residual pressure. If there is, repeat the process to remove any remaining refrigerant until the A/C system holds a stable vacuum for at least five minutes.
What is the minimum system pressure necessary to leak test with an electronic leak detector? A. 25 psi B. 50 psi C. 75 psi D. 100 psi
The correct answer is B. There must be at least 50 psi of refrigerant pressure in the system in order for a leak detector to be able to sense a leak. Refrigerant may have to be added to the system to achieve this.
When filling a container with recycled refrigerant to what percentage should teh container be filled? A. 50 percent B. 60 percent C. 70 percent D. 80 percent
The correct answer is B. To prevent over filling during transfer of refrigerant, never fill a container to more than 60 percent of its gross weight rating.
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
The correct answer is 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.
Vehicles with Dual Zone climate control have a separate _____________ for the passenger side of the vehicle. A. mode door B. blend door C. heater core D. evaporator core
The correct answer is B. Vehicles with Dual Zone climate control have a separate blend door for the passenger side. The passenger can adjust a separate temperature control, which in turn controls the blend door and the amount of air flowing through the heater core for the passenger seat of the vehicle.
When an A/C system is operating, a clicking or buzzing noise is heard coming from the compressor. Technician A says that this noise means that the system is overcharged. Technician B says that the noise could be due to air in the system. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is C. A clicking or buzzing noise coming from the compressor is a sign that the system is overcharged and liquid refrigerant is entering the compressor. Unless some refrigerant is removed, severe compressor damage may result. This noise could also result from air in the system.
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
The correct answer is C. 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.
Which of the following is a true statement regarding R134a refrigerant? A. It is harmful to the ozone layer. B. It mixes with mineral oil. C. It requires a different desiccant than R12. D. It operates at lower pressures than R12.
The correct answer is C. Dessicants are not universal and different types must be used with different refrigerants and lubricating oils. When a system is retrofitted, the replacement receiver/drier or accumulator has XH-7 or XH-9 desiccant.
Technician A says that moisture in an A/C system can freeze in the expansion valve and stop the system from cooling. Technician B says that moisture in the A/C system will react with R12 to form an acid that can cause corrosion. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is C. Moisture in the A/C system can ice up in the expansion valve and block refrigerant flow. On systems with R12, moisture can combine with the chlorine in the R12 to from hydrochloric acid. These chemicals can corrode metals and attack rubber parts.
The A/C compressor cycles rapidly, and air coming from the vents is only slightly cool. Technician A says the problem could be a low refrigerant charge. Technician B says the problem could be a defective thermostatic switch. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is C. During operation, the clutch may cycle on and off several times each minute. Insufficient refrigerant causes rapid change in heat load on the evaporator, which affects system pressures. If the clutch cycles rapidly, it may be a sign of low refrigerant charge. A defective thermostatic switch may not be engaging the compressor clutch long enough. The thermostatic switch has a capillary tube attached to the evaporator outlet or inserted between the evaporator core fins to sense the temperature. This capillary is attached to a switch that opens and closes, as necessary, to cycle the compressor.
Technician A is finishing his repair on a hybrid HV electric compressor and is preparing to recharge the system using a service machine that is used to service he all of the shop's customers cars. In the process, introduces a small amount of PAG oil into the system. Knowing this, which of the following statements is NOT true about what Technician A should do next. A. If the air conditioning compressor has not been engaged, he can replace the compressor and recharge using a service machine dedicated to hybrid service. B. If the air conditioning compressor has been engaged, he will need to follow OEM procedure to remove the contaminated oil charge from the system. C. There is no issue. PAG oil is approved for use in a HV air conditioning system. D. The introduction of the PAG oil remaining in the service machine's internal lines and service hoses enough to cause a HV insulation fault in the hybrid vehicle.
The correct answer is C. Even a minute amount of PAG oil introduced into a HV system can be enough to cause a HV insulation fault. If the compressor has run, and allowed to pump that contaminated oil through the entire system, it may be necessary to replace all the system components in order to correct the problem.
Two Technicians are discussing an A/C system retrofit. Technician A says that a high-pressure cutout switch must be added to the system. Technician B says that the receiver/drier should be replaced. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is C. If it does not have one, a high-pressure cutout switch must be added to the system to stop compressor operation before high-side pressure reaches the point of open ing the high-pressure relief valve and releasing refrigerant into the atmosphere. The receiver/drier should be replaced because all refrigerants do not use the same type of desiccant. R134a systems use XH-7 or XH-9 desiccant.
A customer complains of a foul odor coming from the dash outlets whenever the A/C and blower are on. Technician A says that this is caused by a clogged evaporator drain. Technician B says that this is caused by bacterial growth on the evaporator. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is C. If the drain at the bottom of the evaporator case becomes clogged and water collects and stagnate, or if the surface of the evaporator remains too moist due to high humidity, bacteria can grow in the stagnant water or on the evaporator surface and cause an odor. This odor is then sent into the passenger compartment by the blower motor.
Two technicians are discussing sight glass observations. Technician A says that if foam is seen in the sight glass, the refrigerant charge is low. Technician B says that if oil streaks are seen in the sight glass, the refrigerant charge is low. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is C. If there is foam, the charge is low, but if there are only a couple of bubbles, it is probably okay. A few bubbles when the compressor cycles on is normal. Oil streaks in the sight glass usually indicate a low charge and that the compressor is pumping oil from its sump.
A customer complains that when accelerating his car with the A/C on, the cold air flow from the dash outlets shifts to the floor. Technician A says that this is caused by a faulty check valve in the vacuum reservoir. Technician B says that this condition is due to a vacuum leak. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is C. If, during hard acceleration, air routing changes by itself, it's probably due to a leak in the system or a faulty check valve in the vacuum reservoir. A complaint that the mode shifts from the dash to the floor at wide-open throttle is evidence that the system isn't holding vacuum.
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
The correct answer is C. 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.
All of the following are classifications of antifreeze EXCEPT: A. Inorganic Additive Technology (IAT) B. Organic Additive Technology (OAT) C. Hybrid Inorganic Additive Technology (HIAT) D. Hybrid Organic Additive Technology (HOAT)
The correct answer is C. Inorganic Additive Technology (IAT) antifreeze uses Inorganic phosphates and silicates to provide corrosion protection. Organic Additive Technology (OAT) antifreeze uses organic acids to protect the iron and aluminum ik the cooling system. Hybrid Organic Additive Technology (HOAT) antifreeze uses both silicate and organic acid corrosion inhibitors for extended service life.
During A/C system operation, a knocking sound can be heard coming from the compressor. Technician A says that there could be internal compressor damage. Technician B says that the compressor mounting brackets and bushings should be checked. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is C. Knocking noises from the compressor usually indicate internal damage, especially on piston-type compressors. However, always check the compressor mounting and brackets before condemning the compressor for noise. A loose mounting can cause knocking noises from the compressor area that may be mistaken for internal compressor noise.
During an A/C system performance test, high side pressure was found to be excessive and the A/C compressor continued to run. Technician A says that the high-pressure cutout switch could be defective. Technician B says that there could be an air flow obstruction at the condenser. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is C. Technician A is correct because the high-pressure cutout switch should break the circuit to the compressor clutch if it detects pressures above a preset level. If the compressor continues to run when pressure passes the threshold of the switch calibration, the switch is defective. Technician B is also right because an obstruction to air flow through the condenser can cause excessive high-side pressure.
Which of the following sensors is NOT an NTC thermistor? A. in-vehicle sensor B. ambient sensor C. sunload sensor D. engine coolant temperature sensor
The correct answer is C. The a unload sensor is a photovoltaic diode. All of the other sensors are NTC thermistors.
The inside of an EATC equipped vehicle never feels as cool as the temperature setting. The A/C system checks out OK, including the sensors. Technician A says there could be an obstruction in the aspirator tube. Technician B says the aspirator tube could be disconnected from the duct. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is C. The in-vehicle temperature sensor is located in the aspirator, which is located in the dashboard. The aspirator tube is connected to a heater A/C duct. The air flowing in the duct past the tube creates a vacuum, drawing in-vehicle air past the sensor. If there is an obstruction in the aspirator tube or the tube is disconnected from the duct, air will not be drawn past the in-vehicle temperature sensor and the sensor will not be able to accurately measure the temperature inside the vehicle. This could account for the discrepancy between the temperature setting and the actual temperature inside the vehicle.
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 correct answer is C. 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.
All of the following are true statements about re- ceiver/driers EXCEPT: A. They may have a sight glass located on the top. B. They store liquid refrigerant. C. They keep liquid refrigerant from entering the compressor. D. They contain a desiccant to absorb moisture from the system.
The correct answer is C. The refeiver/drier is located in the high side of the system, between the condenser and evaporator, ahead of the expansion valve. It stores liquid refrigerant until needed by the evaporator. The accumulator is the component that keeps liquid refrigerant from entering the compressor, but accumulator are used in systems with orifice tubes, not expansion valves.
A major cause for the depletion of the ozone layer has been attributed to: A. carbon monoxide (CO) fumes from automotive exhaust B. unburned hydrocarbon (HC) emissions from automobile exhaust C. the release of chlorofluorocarbons (CFCS) into the atmosphere D. all of the above
The correct answer is C. The release of the CFCs into the atmosphere has been found to be a major cause of ozone layer depletion.
The operation of the thermostatic switch depends on the temperature of the: A. condenser B. compressor C. evaporator D. outside air
The correct answer is C. 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.
The following are all methods of orifice tube replacement EXCEPT: A. Replace the line that incorporates the orifice tube. B. Disconnect the liquid line from the evaporator inlet line and pull the orifice tube straight out with an extractor tool. C. Disconnect the liquid line from the evaporator inlet line and, using a twisting motion to break free of the line, pull out the orifice tube with an extractor tool. D. Cut out the section of line containing the orifice tube and, using a kit, install a new orifice tube line segment.
The correct answer is C. When removing the orifice tube with an extractor tool, do not twist or rotate the orifice tube in the line as it can break. If an orifice tube breaks during removal, special tools are available to extract broken orifice tubes. All of the other answers are methods of orifice tube replacement.
A customer complains of low air flow through the instrument panel duct outlets. Which of the following could be the cause? A. faulty blower motor B. clogged passenger compartment air filter C. stuck mode door D. all of the above
The correct answer is D. A blower motor that does not run on high speed or higher speeds due to a defective relay or resistor would cause reduced air flow. A clogged passenger compartment air filter would create an obstruction and also reduce air flow. Finally, a mode door stuck between two positions would create the impression or reduced air flow because the available air would be routed to two places (i.e., the floor and the dash) instead of one.
The high-side pressure in an A/C system is above specifications. All of the following could cause this problem EXCEPT: A. An overcharge of refrigerant B. Restricted air flow across the condenser C. A slipping fan belt D. A broken compressor reed valve
The correct answer is D. A broken compressor reed valve could not cause the high-side pressure to be above specifications.
Low heater output can be caused by all EXCEPT: A: An engine low on coolant B: A stuck open cooling system thermostat C: A restricted heater control valve D: A disengaged clutch type radiator fan
The correct answer is D. A disengaged clutch type radiator fan would not cause low heater output. All of the other answers are possible causes of low heater output.
A system with a low pressure on the low side and a heavy frost accumulation on the inlet side of the Thermostatic Expansion Valve (TXV) indicates a: A. TXV stuck open B. clogged condenser C. defective compressor D. Clogged screen or the TXV stuck closed
The correct answer is D. A low pressure reading in the low side and a heavy frost accumulation on the inlet side of the TXV indicates a clogged screen at the expansion valve inlet or a TXV stuck closed.
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
The correct answer is D. 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.
All of the following could cause poor heater performance EXCEPT: A. defective temperature blend door actuator B. radiator coolant temperature below 150F (66C) C. heater core return hose much cooler than inlet hose D. stuck open heater control valve
The correct answer is D. A stuck open heater control valve could cause problems when heat is not wanted, but because coolant flow to the heater core is not interrupted, the heater valve would not cause poor heater performance. A defective temperature blend door actuator could cause poor heat if the blend door was stuck in the wrong position. Radiator coolant temperature below 150F (66C) would indicate a missing or stuck open thermostat, which could also cause poor heater performance. A heater core return hose that is much cooler than the inlet hose means that the heater core is plugged or air bound, also causing poor heat.
Recovering/recycling equipment must have shutoff valves located within 12-in (30cm) of the hoses' service ends so that: A. oil can be added to the refrigerant B. the unit can be isolated from the refrigerant source C. the filter can be changed without disconnecting the hoses D. refrigerant discharge can be kept to a minimum
The correct answer is D. According to the Clean Air Act, recovery/recycling equipment must have shutoff valves located within 12-in. (30 cm) of the hoses' service ends so that refrigerant discharge to the atmosphere can be kept to a minimum.
During an A/C system performance test, the air temperature at the center outlet duct is warm to slightly cool and the low and high-side pressures on the manifold gauge set are both low. All of the following could be the cause of these symptoms EXCEPT: A. clogged orifice tube B. expansion valve stuck closed C. restricted receiver/dryer D. plugged condenser
The correct answer is D. Although the air temperature at the center outlet would be about the same, if the condenser is plugged, the manifold gauge readings would be high. All of the other answers are possible causes for the symptoms in the question.
A customer with an SATC equipped vehicle complains that the car does not get cool enough on hot days. Technician A says that the blend door actuator is probably malfunctioning. Technician B says that the programmer is the problem. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is D. Both technicians are jumping to conclusions. To find the problem, a logical diagnostic procedure must be followed or partsay be replaced unnecessarily. This includes performing a preliminary inspection of the A/C system and checking refrigerant pressures before condemning any part of the ATC system.
A vehicle comes into the shop with a complaint of "no cold air". Technician A says to first turn the key off, set the DVOM to DC volts and measure the voltage present at the electromagnet clutch. If there is no voltage present, replace the compressor. Technician B says set the DVOM to DC volts and measure the continuity of the compressor clutch. Who is correct? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is D. In the case of technician A, in order to measure voltage present at the compressor clutch, the key must be turned on, A/C set to a cold position and the engine sgouod be running. If there is no voltage present, it would mean there is a problem with the circuit leaking to the compressor clutch coil. In the case of Technician B, in order to measure the compressor clutch continuity, the DVOM would need to be set to the Ohm position not the DC volt position.
A typical refrigerant identifier can detect all of the following EXCEPT: A. R134a B. Hydrocarbons C. Air D. R744
The correct answer is D. Systems that use R744 refrigerant, which is pure CO2, are still under development. Typical refrigerant identifiers that are currently available can detect R12, R134a, R22, air, and hydrocarbons.
Observing the data stream while operating a HVAC system on a late model vehicle the counts for the blend door change when the vehicle is moved outside in the mid day sun. Technician A says there is an intermittent problem with the blend door actuator that will eventually set a DTC. Technician B says that under no circumstances should the counts change on the blend door motor. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
The correct answer is D. The blend door motor counts change as the position of the door is changed. This is its normal operation. The easiest way to determine the blend door is functioning properly is to read the data stream from the scan tool while observing the system operation.
A customer complains about a hissing noise coming from under the hood after turning off the car. A Technician says the noise is coming from the A/C system and is: A. a normal condition B. system pressures equalizing C. a refrigerant leak D. both A and B
The correct answer is D. The hissing noise is normal and caused by high-side pressure going through the refrigerant metering device as system pressures equalize.
All of the following are true statements concerning in-line filters EXCEPT: A. They are usually installed in a system that has suffered a compressor failure. B. They are installed to protect the new compressor from metal chips or other debris that could be in the system from the original compressor failure. C. They are installed to collect debris that could clog the orifice tube or expansion valve filters. D. Filters are only installed in the high side of the system.
The correct answer is D. There are filters that fit into both the high and low sides of the system. All of the other statements are true concerning in-line filters.
To properly an A/C system, the vacuum pump should be operated a minimum of: A. 5 minutes B. 10 minutes C. 20 minutes D. 30 minutes
The correct answer is D. To properly evacuate an A/C system, the vacuum pump should be operated for a minimum of 30 minutes.
