ASE A7 Heating Air Conditioning
Most blower motors use a relay for high speed. Because if the increase of current. A faulty blower motor relay will cause it to stay on? A. Low B. High C. Mid D. Both A and C
Answer A is correct
The fusible metal high pressure relief device are often found on the? A. Receiver/drier B. Accumulator C. Orifice D. B and C
Answer A is correct
What cause the windows to fog ? A. Clogged evaporator drain B. Stuck HVAC control C. Refrigerant leaking D. Frozen evaporator
Answer A is correct
What hose is going from the compressor to condenser ? A. Discharge hose B. Suction hose C. Liquid line D. None
Answer A is correct
When the thermostat (with heat it will open to keep the coolant flowing through to prevent over heat not like other resistors) is stuck open what will happen? A. Engine temp to not reach its operating temp B. Engine will over heat after a load
Answer A is correct
Which sensor/switch uses a variable voltage signal as the engine temp changes ? A. Engine temp sensor B. Power steering switch C. Throttle position sensor D. Steering wheel sensor
Answer A is correct The AC can be deactivated the engine temp gets too high
The pH level are generally between? A. 7.5 to 10 B. 8 to 10 C. 9 to 10 D. 9.5 to 10
Answer A is correct because a lower level means it has acidic and corrosion characteristic that will damage fragile components. A higher level will cause the aluminum to corrode and scale to built up in the engine.
What would happen if the compressor clutch has too little air gab? A. Will likely rub and make noise when it is off B. Will likely slip due to the inability of the coil magnetism to overcome the distant of air gap
Answer A is correct if the compress clutch does not engage it can be test with a ohm meter for high resistance
Which line/hose uses a muffler to limit compressor noise? A. Discharge hose B. Suction hose C. Liquid line D. None
Answer A is correct if the muffler becomes restricted replace discharge line/hose. Always use new gasket and lube rubber seals (not metal seals install dry).
Driving condition, geographic location, and system usage can alter the frequency of service need to replace the cabin air filter. What is the typical interval I should be change ? A. 15,000 to 24,000 B. 24,000 to 38,000 C. 16,000 to 24,000 D. 38,000 to 40,000
Answer A is correct keep in mind if the filter becomes clogged, reduce airflow through the evaporator can affect the system performance and possibly result in evaporate freeze up.
High-pressure switch is known as ? (2wire) A. Pressure cut-off switch B. Pressure cycling switch C. Binary pressure switch D. A/C pressure transducer E. Thermostatic switch F. Thermistor fin temp sensor G. Thermal limiter
Answer A is correct opens under high A/C pressure (opens at 450-490PSI; closes at 250-275PSI)
Once coolant acidity increase it begins to have some characteristics of a DC battery. This is static coolant voltage. It's usually present when? A. Off B. On C. Disconnected D. Neither
Answer A is correct the specs for this test is .2 V. If the static voltage is too high it's time to drain and fill the coolant system
If the compressor has loose fastener are loose what kind of noise would it make? A. Knocking B. Clunking C. Thumping D. None of the above
Answer A is correct this will only happen when the compressor is engage.
Which device needs 70% psi of static pressure in the system to find leaks ? A. Electronic detector B. Nitrogen injection C. Due and black-light D. Vacuum pump
Answer A is correct, make sure to turn the electronic detector on and let it warm up then slowly move it through the A/C system without covering the tip with dirt.
Before recycling refrigerant tested for non-condensable gases it should be placed in a _____ area for no less than 12 hours. A. Cool B. Hot C. Clean D. Dirty
Answer A is correct, the ambient temp may be as low as 65 degrees F. Compare temp and pressure reading with an appropriate pressure limit chart.
A vehicle has poor air conditioning performance. The customer has added R134a refrigerant to the system. Technician A says to use a refrigerant identifier. Technician B says refrigerant mixtures are not recommended, but will not affect system pressures. Who is correct?
Answer A is correct. Use a refrigerant identifier to identify R12, R134a, R22, hydrocarbons and air.
If the receiver/drier is on the high side of the system then the system is a ? A. Orifice tube B. TXV system C. Explanation valve D. Not here
Answer B is correct
Some high pressure relief valve are spring loaded and self-resetting. Self- resetting high pressure the are normally found on the ______ head of the compressor? A. Front B. Rear C. Side D. None
Answer B is correct
What hose is going from the evaporator to compressor ? A. Discharge hose B. Suction hose C. Liquid line D. None
Answer B is correct
When the thermostat (with heat it will open to keep the coolant flowing through to prevent over heat not like other resistors) is stuck close what will happen? A. Engine temp to not reach its operating temp B. Engine will over heat after a load
Answer B is correct
Which switch/sensor opens when ugh pressure is experienced? A. Engine temp sensor B. Power steering switch C. Throttle position sensor D. Steering wheel sensor
Answer B is correct The AC can be deactivated when the power steering switch opens and parking maneuvers to prevent excessive load on the engine
A worn motor can sometimes will cause a ? A. Knocking sound B. Fuse blown C. Crunching sound D. None
Answer B is correct because if the increase of physical resistance.
If the air gap it too wide in a A/C compressor what would happen? A. Will likely rub and make noise when it is off B. Will likely slip due to the inability of the coil magnetism to overcome the distant of air gap
Answer B is correct if the coil fails you could supply voltage to see if the clutch engages if not ohm test it.
A failing compressor that creates a load knocking noise will often send ___ particles? A. Copper B. Metallic C. Bronze D. Aluminum
Answer B is correct if the compressor is engage, it is usually the compressor that is faulty
Refrigerant containers should be check for non-condemnable gas. It should be placed out of sunlight @ _______ degrees for ________ hours and a thermometer should be placed 4 inches from container surface. A. 65, 6 B. 65, 12 C. 75, 6 D. 75, 12
Answer B is correct if the pressure is less than specs. it is ready for use.
When there is a poor ground in the vehicle, the cooling system tends to be a path for electrical flow. Dynamic coolant voltage is only present when? A. Off B. On C. Disconnected D. Neither
Answer B is correct if the voltage is .3 V or higher, and then look for poor ground.
Which leak detector uses intertwined pressurized gas to find the leaks ? A. Electronic detector B. Nitrogen injection C. Due and black-light D. Vacuum pump
Answer B is correct it is advisable to inject the system with 120 psi of nitrogen. After injecting the system look for pressure drops or by using a listening tool to listen for a hissing sound
Low-pressure switch is known as ? (2wire) A. Pressure cut-off switch B. Pressure cycling switch C. Binary pressure switch D. A/C pressure transducer E. Thermostatic switch F. Thermistor fin temp sensor G. Thermal limiter
Answer B is correct it opens under low A/C conditions specs: (opens at 15-25 PSI: closes at 35-40 PSI)
What temp should the duct be ? A. 30 degrees to 40 degrees F B. 40 degrees to 50 degrees F C. 50 degrees to 60 degrees F D. 60 degrees to 70 degrees F
Answer B is correct the low side pressure should be approximately 20 to 40 PSI when operating. And high side should be 2 or 3 times depending on the ambient temp.)
If the system is always hot (heating) even when on the cold setting, you must check the? A. Metering valve B. Control valve C. Check valve D. Schroeder valve
Answer B is correct this device meter is the amount of coolant that enters the Hester core
A vehicle's air conditioning performance is reduced at low speeds and stop lights, but cools at highway speeds. Which of these is MOST likely the cause of this condition? A. A low refrigerant charge. B. A missing fan shroud. C. A normal condition. D. A faulty compressor clutch relay.
Answer B is correct. A properly fitting and fastened fan shroud is vital for good A/C and engine performance. Many of these shrouds and dams create a low pressure area behind the radiator and condenser. Loose or missing shrouds will be especially noticeable as the vehicle slows and ram air is reduced.
R 134a Refrigerant: A. Changes from a vapor to a liquid as it absorbs heat. B. Containers are sky blue colored. C. Has a very high boiling point. D. Is a CFC that contains chlorine.
Answer B is correct. An R134a refrigerant system has less refrigerant capacity than a similar R12 system. They also have different pressure characteristics. R134a is contained in a sky blue container, R-12 is contained in a white container.
The high side pressure will be about ___ times the ambient temperature with a low to moderate humidity levels and as much as _____ times of ambient temp with high levels of humidity. A. 1, 2 B. 2, 2 C. 2, 3 D. 2, 4
Answer C is correct
What are the main causes that can occur at the heater core ? A. Leaks B. Restrictions C. Both D. Neither
Answer C is correct A leaking heater core is typically cause a distance coolant odor in the cab if a large it can run out of the drain tube (HVAC system)
Failure to sue the correct out will cause ? (Lack of lubricantion) A. Damage to the condenser B. Damage to evaporator C. Damage to the compressor D. All the above
Answer C is correct R-134a uses only synthetic oil, polyalkylene glycol (PAG) there's are a number of different blends of PAG always use the recommended one for the system. R-12 uses mineral oil because it doesn't break down the R-12.
What affects the A/C by using engine speed ? A. Engine temp sensor B. Power steering switch C. Throttle position sensor D. Steering wheel sensor
Answer C is correct The AC is typically turned off when high levels of throttled are seen
What could cause the windows to fog up but also have a odor with associate and worsens when the defroster is turned on? A. Evaporator core B. Condenser C. Heater core D. Evaporator drain tube
Answer C is correct and if this isn't repaired it will cause problems with engine coolant levels being reduced.
-Connect a pressure manifold set to the vehicle high- and low-side test fitting -Insert a thermometer into the center A/C duct. -Adjust the AC controls to Max AC with the blower on high-speed -Increase the engine speed from 1500 to 2500 RPM -Shut windows and doors on the test vehicle. -After five minutes, read the high and low side pressure's and the duct temperature. These are some test to test the ??? A. A/C unit B. Blower motor C. Performance test D. All the above
Answer C is correct because this is a performance test
On a orifice tube metering device system if refrigerator is been added what could happen? Tech a says this could cause the system to have high pressure on both sides. Tech B says this could cause the accumulator to become clogged. A. A B. B C. Both D. Neither
Answer C is correct because to much refrigerant will cause both sides to have high than normal pressure. It could also cause the accumulator to suck in to much liquid and clog the system
What cause the the window to have an oily film A. Clogged evaporator drain B. Stuck HVAC control C. Refrigerant leaking D. Frozen evaporator
Answer C is correct is is caused by it leaking onto the evaporator core and has allowed some refrigerant to escape into the evaporator case.
Dual pressure switch is known as? (3wire) A. Pressure cut-off switch B. Pressure cycling switch C. Binary pressure switch D. A/C pressure transducer E. Thermostatic switch F. Thermistor fin temp sensor G. Thermal limiter
Answer C is correct opens at high pressure and low pressure. Located on the HIGH side.
Which 2 type of TXV variable metering device are there? A. Capillary style B. Block style C. Both D. Cone style
Answer C is correct the capillary style is located inside the HVAC duct box, and the block style is usually located in the firewall. BOTH have sensing device that open and close when temps are to hot or to cold. (Open when hot for more refrigerant to pass and close for cold) this will prevent evaporator to freeze up. (Thermal type switch)
What are the two different type of orifice tube ? A. Fixed B. Variable C. Both D. Accumulator
Answer C is correct the fix is mounted somewhere on the liquid line and it's job is to meter low-pressure atomized liquors so I can vaporize. The variable is usually on police and taxi cars because it changes size as temp load change. This prevents the evaporator core from getting flooded during long periods of vehicle idle.
When the compressor is operating, a loose compressor mount or bracket may ? A. Pulse B. Knock C. Vibrate D. All the above
Answer C is correct this noise/feeling will usually stop when the compressor is disengage.
When replacing high pressure valve is best to replace it ? A. When cold B. When hot C. With one similar to specs D. All the above
Answer C is correct unless it being retrofitted to use 134a refrigerant instead of r-12
Which leak detector injects a fluorescent dye into the A/C system and operate it? A. Electronic detector B. Nitrogen injection C. Due and black-light D. Vacuum pump
Answer C is correct, if the evaporator is suspected for leaks you can check it at the drain tube for the dye
A/C system need to be evacuated for about? A. 10 mins B. 20 mins C. 30 mins D. 40 mins
Answer C is correct, it should last for 30 mins and should have 0 PSi when done if not keep evacuate until it is 0. Also it's to remove any moisture in the system.)
An air conditioning system with a variable displacement compressor has poor performance in high demand situations. All of these could be the cause EXCEPT: A. A low refrigerant charge. B. A faulty control valve. C. A faulty low pressure switch. D. A weak compressor.
Answer C is correct. A variable displacement compressor uses a control valve to alter system pressures. A cycling clutch orifice tube system has a pressure cycling switch on the low side of the system, often located on the accumulator.
A manifold gauge indicates a system has low discharge pressure. The MOST likely cause of this condition is: A. A restricted condenser. B. A loose fan belt. C. A damaged compressor reed valve. D. A broken compressor piston.
Answer C is correct. Damaged reed valves or plates result in low discharge pressure.
A vehicle's air conditioner blows cold air at normal speeds, but warm air while sitting at stop lights. The LEAST likely cause of this condition is: A. An overheating engine. B. A weak electric fan motor. C. A frozen expansion valve. D. Debris in the condenser fins.
Answer C is correct. This is a least likely type question. Once the expansion valve freezes, the air conditioning would have poor performance at all speeds.
All these statements are true about a throttle position sensor EXCEPT: A. It indicates throttle position to the engine control module. B. The control module disengages the A/C clutch at wide open throttle. C. The ECM disengages the A/C clutch at idle. D. The throttle position sensor signal is used to indicate throttle angle.
Answer C is correct. This is an except question. All the other choices are true except this one. The compressor's clutch is not disengaged at idle, it's disengaged at WOT providing additional power when needed.
When A/C performance is insufficient there's are some conditions to look for: Refrigerant over charge, airflow problem at the CONDENSER, refrigerant undercharge, metering device restrictions, faulty compressor (not engaging), and? A. Faulty Compressor (reed valve damage) B. High side internal restriction C. Excessive air in the A/C system D. All the above
Answer D is correct (These cause low pressure for refrigerant undercharge, metering device restriction, and air flow problem at the condenser. For high pressure is refrigerant overcharge.)
Thermostatic clutch fans lock up when the engine temp rises. The centrifugal fan clutch tries to maintain consistent speed regardless of engine speed. What are the two common failures in these system? A. No fan clutch engagement at all B. Completely locked up clutch C. Leaking refrigerant D. Both A and B
Answer D is correct The first will result in poor air-conditioning efficiency and overheating in traffic. The second one will result in a complaint that the vehicle sounds like an airplane and that there is a loss of power as it can take up to additional 17 hp to drive one of the multi blade fans in a fixed mode at highway speed.
What components is located in the low side and is at the outlet of the evaporator A. TXV (receiver/drier) B. Condenser C. Compressor D. Orifice tube (accumulator)
Answer D is correct and it's function is to prevent liquid from entering the compressor.
The freeze point of a coolant can be test by? A. Test strips B. Hydrometer C. Refractometer D. All the above
Answer D is correct both the refractometer and hydrometer test the weight of the antifreeze concentration level.
Pressure sensor is known as ? 3wire A. Pressure cut-off switch B. Pressure cycling switch C. Binary pressure switch D. A/C pressure transducer E. Thermostatic switch F. Thermistor fin temp sensor G. Thermal limiter
Answer D is correct it is located on the HIGH side. This senses pressure in the high side by vary voltage level.
TXV A/C system is usually near the outlet of the condenser. It filters any moisture that is present. What are some of the features? A. High-pressure fittings B. A pressure relief valve C. Slight glass D. All the above
Answer D is correct the slight glass is used to determine the state and conditions the refrigerant is in. It should be change when another component is being replaced or if it has been expose to the atmosphere air for too long.
Closely controlling the pressure in the evaporator is one way to manage performance of the A/C system. Many older system use metering refrigerant into he evaporator core. Evaporator controls ? A. Evaporator pressure regulator (EPR) B. Pilot-operated absolute valve (POA) C. Suction throttling valve (STV) D. All the above
Answer D is correct this maintain the back pressure in the evaporator. Because of the temp and pressure relationship, the effect is to regulate evaporator temp. The temp is control to a point that provides effective air cooling but prevents the freezing of moisture that condenses on the evaporator.
There are two ways of calibrating the dual/multi-zone HVAC system. Which one is is? A. Manual self diag mode B. Scan tool C. Auto self diag mode D. A and B
Answer D is correct which is done by pressing two of the control head buttons in the particulars sequence
Which lead detector is very effective before recharging the system? A. Electronic detector B. Nitrogen injection C. Due and black-light D. Vacuum pump
Answer D is correct, after evacuating the system look at the low side for lost of vacuum. A seal system would hold vacuum.
Refrigerant storage should be filled to _____ percent of there gross weight rating. A. 30 B. 40 C. 50 D. 60
Answer D is correct, the refrigerant must be evacuated to 17 in. Hg before placed in container
During a performance test on a CCOT system the manifold gauge indicates that the high side pressure is low and the low side pressure is high. This is caused by a: A. Stuck open expansion valve. B. Frozen expansion valve. C. Restricted condenser. D. Faulty compressor.
Answer D is correct. A high low side and a low high side indicates a faulty A/C compressor.
During an initial inspection, the technician notices that one line on the receiver drier is cooler than the other. This is caused by: A. Nothing it's a normal condition. B. A low refrigerant charge. C. Too much oil in the system. D. A restriction in the receiver drier.
Answer D is correct. A restriction in the receiver drier will result in a change in line temperatures. This is because one of the properties of refrigerant is that it changes temperature along with pressure. The restriction has altered pressure in the drier and lowered the temperature of the outlet line.
All of these are true about an accumulator EXCEPT: A. It is located on the low side of the system. B. It prevents excess liquid from entering the compressor. C. It contains a desiccant capable of absorbing moisture from the refrigerant. D. This system contains a thermostatic expansion valve to meter the refrigerant.
Answer D is correct. An accumulator is used on a CCOT or Cycling Clutch Orifice Tube type system.
All of these are true about an air conditioner's evaporator EXCEPT: A. It removes humidity from the air. B. Refrigerant flows from the bottom to the top. C. Refrigerant enters the evaporator as a liquid. D. The refrigerant changes from a vapor to a liquid as it receives heat from the cabin air.
Answer D is correct. The refrigerant converts from a liquid to a vapor, because it boils as it receives heat from the cabin air. Refrigerant has a very low boiling point.
An air conditioning system contains a thermostatic expansion valve. The suction line leading to the compressor is cool to the touch. This indicates: A. A stuck open expansion valve. B. A low refrigerant charge. C. A stuck closed expansion valve. D. A normal condition.
Answer D is correct. This is a normal condition.
Evaporator temp sensor is known as ? (2wire) A. Pressure cut-off switch B. Pressure cycling switch C. Binary pressure switch D. A/C pressure transducer E. Thermostatic switch F. Thermistor fin temp sensor G. Thermal limiter
Answer E is correct opens when cold temps are experienced in evaporator.
Evaporator known as ? (2 or 3wires) A. Pressure cut-off switch B. Pressure cycling switch C. Binary pressure switch D. A/C pressure transducer E. Thermostatic switch F. Thermistor fin temp sensor G. Thermal limiter
Answer F is correct sense temp in evaporator using variable signal.
What is located in the compressor? A. Pressure cut-off switch B. Pressure cycling switch C. Binary pressure switch D. A/C pressure transducer E. Thermostatic switch F. Thermistor fin temp sensor G. Thermal limiter
Answer G is correct it interrupts power to the compressor when temps are getting high.
An EATC (electrical auto temp control) air conditioning system has low fan speed operation during high demand situations, like in direct sunlight. Technician A says this is because something is covering the sun load sensor's photo diode. Technician B says a sun load sensor is a variable resistor and can be tested with an ohmmeter. Who is correct?
Both technicians are correct.
Technician A says refrigerant flows from the top of the condenser to the bottom. Technician B says a restriction in a condenser can cause damage to the compressor. Who is correct?
Both technicians are correct.
The compressor is rapidly cycling on and off on a CCOT air conditioning system. Technician A says this condition can be caused by a low refrigerant charge. Technician B says this could be caused by a faulty clutch cycling switch. Who is correct?
Both technicians are correct.
The in-cabin temperature sensor is suspected for an air conditioner's poor performance. Technician A says the in-cabin temperature sensor is a NTC that should be tested for resistance with an ohmmeter. Technician B says the aspirator may be disconnected from the vent system. Who is correct?
Both technicians are correct.
Two technicians are discussing refrigerant storage. Technician A says HFC-134a is contained in a sky blue container. Technician B says CFC-12 is contained in a white container. Who is correct?
Both technicians are correct. (HFC-134a) R-134a is stored in a sky blue container with a sky blue label, and (CFC-12) R-12 is stored in a white container with a white label. Each refrigerant has its own color assignment. R-12's assignment is white and R-134a is sky blue "light blue".
An air conditioning system blows only warm air when the heater is on high output. Technician A says this could be a faulty heater control valve. Technician B says this could be caused by the cooling system's thermostat. Who is correct?
Both technicians are correct. A restricted heater control valve will leave a vehicle with low heater performance. A stuck open thermostat has a negative effect on the heater's performance.
Technician A says the expansion valve is located on the inlet port of the evaporator. Technician B says the expansion valve's temperature sensing bulb is located near the outlet port of the evaporator. Who is correct?
Both technicians are correct.An expansion valve is at the inlet port of the evaporator and the sensing bulb is placed on the outlet port.
An air conditioner with an expansion valve performs poorly only during the hottest times of the day. Technician A says the receiver drier may be saturated. Technician B says there may be moisture in the refrigerant. Who is correct?
Both technicians are correct.The receiver drier contains a desiccant that must be changed after it's been exposed to moisture. If saturated with moisture, the excessive moisture in the drier will flow to the expansion valve and freeze, reducing system performance. Poor system performance is most noticeable during the hottest times of the day.
A frozen spot is noticed in the center of the condenser. Technician A says a frozen spot on a component or connection indicates a restriction in the system. Technician B says this is caused by a clogged orifice tube. Who is correct?
TECH A is correct. A restriction in a line or component acts like a metering device and changes the system's pressure. The change in pressure results in a change in temperature.
Two technicians are discussing an inoperative electric blend door in an automatic air conditioning system. Technician A says to inspect the blend door's wiring and connections for an open circuit. Technician B says to troubleshoot this circuit with a test light. Who is correct?
TECH A is correct. An open in the circuit would prevent the blend door's motor operation.
During a visual inspection an oily spot is found on a hose leading from the compressor. Technician A says there may be a refrigerant leak in the system. Technician B says today's R134a systems use mineral oil instead of the older R12 compatible PAG oil. Who is correct?
TECH A is correct. Finding an oily spot on an A/C hose is a quick and easy way to spot a refrigerant leak. Closer inspection and testing will be necessary.
Technician A says the clutch relay protects the control head from the clutch circuit's high current. Technician B says open clutch relay windings result in compressor clutch engagement at all times. Who is correct?
TECH A is correct. Technician A is correct. A relay is a device used to protect control devices like PCM's from the high current used to power devices like an A/C clutch or a radiator fan.
Technician A says while performing a retrofit from R-12 refrigerant to R134a refrigerant, the refrigerant must be recovered into a dedicated cylinder, they cannot be mixed. Technician B says R-12 refrigerant functions at higher pressures than R-134a refrigerant does. Who is correct?
TECH A is correct. The two refrigerants cannot be mixed. A separate, dedicated R-12 refrigerant container is used. Each refrigerant has its own color assignment. R-12's assignment is white and R-134a is sky blue "light blue".
A CCOT (cycling clutch switch orifice tube) system has a high high side. Technician A says to suspect the thermostatic expansion valve. Technician B says this system contains an orifice tube. Who is correct?
TECH B is correct. A clogged orifice tube will result in high high side pressure. It can become clogged with contaminants, debris from a damaged compressor, or a broken desiccant bag releasing desiccant into the refrigerant.
Two technicians are discussing a CCOT air conditioning system. Technician A says the system's pressure cycling clutch switch contains a bulb placed on the inlet port of the evaporator core. Technician B says a pressure cycling switch is located on the low side of the system. Who is correct?
TECH B is correct. A typical pressure cycling switch is located on the accumulator or the low side of a system.
A (TXV) thermostatic expansion valve system blows cold air for five minutes and then goes warm. Technician A says this condition is caused by a low refrigerant charge. Technician B says this condition is caused by moisture in the system. Who is correct?
TECH B is correct. After a few minutes moisture freezes in the expansion valve restricting refrigerant from entering the evaporator core. A saturated receiver drier will result in this condition.
A technician is diagnosing a vehicle's air conditioning system. The vehicle has good engine performance, but the air conditioner is blowing warm air only. A yellow substance is noticed around the evaporator case drip tube. Technician A says this is coolant leaking from the heater core. Technician B says this is fluorescent dye leaking from the evaporator core. Which technician is MOST likely correct?
TECH B is correct. Dye is injected into a system with hard to find leaks. Note that a R-12 system uses one type of dye and a R-134a system uses another. The dye used with R-134a shows up fluorescent yellow. This is brought to light with a special light and glasses.
Technician A says an ambient temperature sensor senses cabin air temperature. Technician B says a faulty ambient temperature sensor can prevent compressor clutch engagement. Who is correct?
TECH B is correct. The automatic temperature control module uses several input sensors. The ambient or outside air temperature sensor is a variable resister. If the outside temperature is colder than the factory set value, or the sensor or it's circuit is faulty, the automatic temperature control will not engage the compressor clutch.
A blower motor operates only in high speed. Technician A says there could be a short in the motor's power feed. Technician B says it may have a faulty blower motor resistor. Who is correct?
TECH B is correct. The blower resister's lower speeds share the same power source and offer varying resistance, while the high speed selection is on it's own circuit and has no resistors.
Technician A says a fixed orifice tube varies the flow of refrigerant in relation to temperature. Technician B says a fixed orifice tube is located between the condenser and the evaporator. Who is correct?
TECH B is correct. The fixed orifice tube is located between the condenser and evaporator core.
A compressor clutch coil is being tested. There is 12 volts at the connector and the ground is good. The resistance of the coil is 0.00 Ohms. Technician A says the coil has an open in it's windings. Technician B says the clutch coil has a short and has failed the resistance test. Who is correct?
TECH B is correct. The test indicates that the circuit is providing within a volt of battery/charging voltage which is good, but indicates that there's a short in the coil. The clutch coil must be replaced.
A squeal is heard only when the compressor clutch first engages. Technician A says this is caused by a loose serpentine belt. Technician B says this is caused by a worn clutch pulley bearing. Who is correct?
TECH A is correct. A loose serpentine belt will cause a squeal when the clutch first engages.
If the accumulator drier is in the low side of the system then the system is an? A. Orifice tube B. TXV system C. Explanation valve D. Not here
Answer A is correct
If the exit heater hose is more than 12-degrees cooler than the inlet, then the heat core is likely? A. Restricted B. Leaking C. Both D. Neither
Answer A is correct
If the low side pressure rises above 0 If means ? A. Refrigerant is still in the system B. Refrigerant is fully out of the system
Answer A is correct
If there is oily residue near the front pulley if the compressor what could this be? A. Leaking front shaft seal B. Leaking rear shaft seal C. Faulty compressor D. All the above
Answer A is correct
Tech A says if the low side pressure is lower than specs and the high side is higher than specs the vehicle has a restriction. Tech B says if the low side pressure is higher than specs and the high side is higher than specs the vehicle has cooling problems. A. A B. B C. Both D. Neither
Answer A is correct
potentiometer is a? A. Variable resistor B. Diode C. Fuse D. Fix resistor
Answer A is correct an instrument for measuring an electromotive force by balancing it against the potential difference produced by passing a known current through a known variable resistance.
A vehicle has a DTC for an A/C Pressure Sensor. What is the first suggested test procedure? A. Power B. Low Reference C. Ground D. Signal
Answer B is correct
A vehicle has the listed A/C Performance data. What is the most probable cause? Ambient Temperature 85F Humidity 50% Low Side Pressure 15 psi High Side Pressure 275 psi Discharge Temperature 75F A.low side restriction B.high side restriction C.TXV stuck open D. Restricted air flow
Answer B is correct
Customer states the vehicle cools for about an hour then will blow hot. Tech notice the evaporator has a sensor. What could this be? A. Frozen evaporator B. Low refrigerant C. Overcharge D. All the above
Answer B is correct
Tech A says if the low side pressure is lower than specs and the high side is lower than specs the vehicle has restriction. Tech b says if the low side pressure is lower than specs and the high side is lower than specs the vehicle has low refrigerant. A. A B. B C. Both D. Neither
Answer B is correct
What is the first step when using an electronic leak detector A. calibrate it for 134a B. allow it to warm up C. test the sample bottled. D. all the above
Answer B is correct
Customer states the vehicle cools for about an hour then will blow hot. The customer will shut the vehicle off for 10 mins and reset it will cool again. What could this be? A. Refrigerant low B. Frozen evaporator C. Both D. Neither
Answer C A is the most likely but B could also be a factor.
If both pressure are reading normal but the vehicle is not cooling. What could cause this ? A. Restriction B. Overcharge C. PAG oil over fill D. All the above
Answer C is correct
The outlet line of the outlet line of the evaporator is warmer than the inlet line. What is the most probable cause? A. restriction in the accumulator B. system over charged C. low refrigerant charge D. restricted air flow
Answer C is correct
The technician is testing the A/C Compressor Relay circuits. What is the expected results at terminal 85? A.battery power B.reference voltage C.ignition power D. none
Answer C is correct
What is achieved by evacuating the system A.air is removed B.refrigerant is removed C.moisture is removed
Answer C is correct
What line is going from the condenser pass the metering device to evaporators ? A. Discharge hose B. Suction hose C. Liquid line D. None
Answer C is correct
Tech A says if the low side pressure is higher than specs and the high side is higher than specs the vehicle has cooling problem. Tech B says if the low side pressure is higher than specs and the high side is higher than specs the vehicle is overcharged. A. A B. B C. Both D. Neither
Answer C is correct (what are some cooling problems? Restricted condenser/radiator) Malfunctioning cooling fans
If the coolant level is 50% and 50% water. The boiling point will increase this will increase the? A. Life B. Freezing point C. Pressure D. None
Answer C is correct. This would lower the freezing point
Tech A says if the low side pressure is higher than specs and the high side is lower than specs the vehicle has restriction. Tech b says if the low side pressure is lower than specs and the high side is lower than specs the vehicle has low coolant. A. A B. B C. Both D. Neither
Answer D is correct (if the low side is higher than specs and the high side is lower than specs 2 faults can cause this. 1 is compressor stuck at high displacement or Expansion device is stuck open.)
There's many sensor in the HVAC system some like cabin air temp sensor, ambient air temp sensor, sun/light sensor, digital control head, coolant temp sensor, and? A. Temp door position sensor B. Mode door position sensor C. Fresh/ recirculated door position sensor D. All the above
Answer D is correct these outputs from a logic board to command the HVAC door, the blower motor, the AC clutch, and the ECM to control temps of the passenger compartment
Two technicians are discussing electric cooling fans and air conditioning performance. Technician A says electric fans regulate refrigerant temperatures more precisely than belt driven fans do. Technician B says electric cooling fans are controlled by control modules that use temperature and pressure actuated sensors and switches. Who is correct?
BOTH TECH A AND TECH B. Electric fans offer more precise control than the conventional belt driven fans do. They're important for engine cooling, air conditioning and heater performance. These fans are controlled by a control module that uses pressure and temperature actuated sensors and switches.
The carpet is wet on the passenger's side of a vehicle. Technician A says this may be caused by a leaking heater core. Technician B says this could be caused by a clogged evaporator case drain tube. Who is correct?
Both technicians are correct
A gurgling sound is heard coming from inside the dashboard of a vehicle. Technician A says this is air trapped in the heater core. Technician B says this noise can be caused by a blown head gasket. Who is correct?
Both technicians are correct.
Technician A says evacuating an air conditioning system will remove air, debris, and moisture. Technician B says to evacuate the system any time it's been exposed to the atmosphere. Who is correct?
TECH B is correct. Always evacuate the system if it's been exposed to the atmosphere.
