ASE A7 HVAC(Heating, Ventilation, Air Conditioning)2022

Tech A says that evacuating an AC system will remove air and moisture from the system. Tech B says evacuating an AC system removes dirt particles. Who is right? A. Evacuating the system removes air and moisture. The receiver drier may contain a filter or strainer to catch and trap foreign particles and dirt, but this remains in the drier and is not removed during evacuation. There is a growling/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.Tech A says that a bad compressor bearing could be the cause. Tech B says that a bad compressor clutch bearing could be the cause. Who's correct? B. The compressor clutch bearing allows the rotor/pulley assembly to spin independently of the compressor shaft when the AC is off. When the AC is on, the rotor/pulley assembly and the armature are locked together by the magnetic action of the compressor clutch coil. The readings on a manifold gauge are 5psi low and 80 psi high with the AC system operating at an ambient temp of 85 degrees Farenheit. What do the readings indicate? Normal operation, low refrigerant level, a restriction on the high side, or a damaged compressor? B. Low pressure on both the high and low side indicates a low refrigerant charge. Recovery/recycling equipment must have shutoff valves located within 12 in of the hose's service ends so that: oil can be added to the refrigerant the unit can be isolated from the refrigerant source the filter can be changed without disconnecting the hoses refrigerant discharge can be kept to a minimum D. According to the Clean Air Act, recovery/recycling equipment must have shutoff valves located within 12 in. of the hoses' service ends so that refrigerant discharge to the atmosphere is kept to a minimum. When recovering refrigerant from an AC system how long should the tech wait after the recover/recycle unit has been turned off to check residual pressure in the system? 1 minute 5 minutes 10 minutes 15 minutes B. the tech should wait five minutes and watch the gauges to check for residual pressure. If there is, repeat the process to remove any remaining refrigerant until the AC system holds a stable vacuum for 5 min. A system with a low pressure on the low side and heavy frost accumulation on the inlet side of a TXV indicates: TXV stuck open Clogged condenser Defective compressor clogged screen or TXV stuck closed D. A low pressure reading on the low side and a heavy frost accumulation on the inlet side of the TXV indicates a clogged screen at the expansion valve or a TXV stuck closed. A blower motor only works on high. Which of the following is most likely? Defective blower relay Defective resistor Defective blower switch Blown fuse or tripped circuit breaker B. D is incorrect because if the blower fuse 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 mostly likely cause for operation on high only is that a portion of the resistor assembly is burnt out. A customer complains that when accelerating his car with the ac on the cold air flow from the dash outlets shifts to the floor. Tech A says that this is caused by a faulty check valve in the vacuum resevoir. Tech B says this condition is due to a vacuum leak. Who is correct? C. If, during hard accel, air routing changes by itself, it's probably due to a leak in the system or a faulty check valve in the vacuum resevoir. A complaint that the mode shifts from dash to floor at WOT is evidence that the system is not holding vacuum. When pressure testing the cooling system on a late model gas engine the pressure on the tester drops but no leaks can be found in the engine compartment. Tech A starts the engine and seeing the pressure on the tester increase says that there is an internal leak, a blown head gasket. Tech B says that there cannot be an internal leak because the engine oil looks normal, not milkly like it would be if coolant were present, and there is no white smoke coming from the exhaust pipe. Who is right? 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 tailpipe but since this is a late model gas engine equipped with a CAT converter, there is no white smoke from the exhauset because the converter super heats the coolant into such a fine vapor that it is not noticeable. When IDing an AC system Tech A says that an accumulator located between the evaporator and the compressor is an indication that the system has an orifice tube. Tech B says that when the high side service port fitting is small er than the one on the low side the system uses R134A. Who is right? 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. Tech B is wrong because on R 134A the low side service port is the smaller one. When troubleshooting an ATC system the system responds when the ambient and in vehicle temp sensors are heated and cooled. However there is no response when the sunload sensor is exposed to a light source. Tech A says that the problem is with the system's programmer. Tech B says it is probably the sunload sensor. Who is correct? B. If the system reacts with a change to one or two inputs but not to 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. The following are all methods of orifice tube replacement EXCEPT: Replace the line that incorporates the orifice tube Disconnect the liquid line from the evap inlet and pull the tube out with the extracting tool Disconnect the liquid line from the evap inlet line, using a twisting motion, pull the orifice tube out with the extractor tool Cut out the section of line that contains the orifice tube and using a kit install a new orifice tube segment. C. When removing the orifice tube with an extractor tool, do not twit 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. When converting the ac system in an older vehicle to R134a what percentage of the original R12 charge amount should be used? 75% 100% 90% 89-90% D. When charging a retrofitted system with R134a refrigerant the system will only require 80-90% of the R12 charge amount. A vehicle with R134a refrigerant inthe ac system has a refrigerant leak. Tech A says that a propane gas leak detector should be used to find the leak. Tech B says an electronic detector should be used. Who's right? Tech A is wrong because propane gas leak detectors cannot detect R134a. Which of the following is a TRUE statement about R134a? It is harmful to the ozone It mixes with mineral oil It requires a different dessicant than R12 it operates at lower pressures than R12 C. Desiccants are not universal and different types must be used with differetn refrigerants and lubricating oils. When a system is retrofitted the replacement drier or accumulator has XH7 or XH9 desiccant. The compressor in an AC system does not run. When a jumper wire is used to connect the battery positive terminal to the power connector the clutch engages. Tech A says the clutch coil is bad. Tech B says the pressure cycling switch could be defective. Who's right? B. A is wrong because if the clutch coil was defective the compressor clutch would not engage. B is correct because, since the compressor engages when 12v is directly applied, the problem is in the control circuit which includes the pressure cycling switch. The floor inside a vehicle is wet and there is a slimy film on the windows. Tech A says the heater core is leaking. Tech B says the evaporator case drain plug is clogged. Who is right? A. Fogged windows that smear when wiped and moisture on the passenger floor are telltale signs of a leaking heater core. Tech B is incorrect because while a clogged evap case drain could cause the case to fill up with moisture and spill onto the floor, it would not cause a slimy film on the window. During AC system operation a knocking sound can be heard coming from the compressor. Tech A says there can be internal compressor damage. Tech B says that the compressor mounting brackets and bushings should be checked. Who is right? C. Knocking noises usually indicate internal damage especially on the piston type compressors. Howerver, always check the 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 noise. All of the following could cause poor heating performance EXCEPT: Defective temperature blend door actuator Radiator coolant temp below 150 degrees Heater core return hose much cooler than inlet hose stuck open heater control valve D. A stuck open heater control valve woulc 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 performance. During a performance test the air temp 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: Clogged orifice tube Expansion valve stuck closed Restricted reciever drier Plugged condenser Although the air temp at the center outlet would be about the same, if the condenser is plugged, the manifold gauge readings would be high.