Automotive HVAC
The Clean Air Act (CAA) ________.
All of the above (mandates that each shop maintain a current government-issued license, outlines the specific refrigerants that can be safely used for each application, sets the standards for shops that do air-conditioning work)
The ______ is one of the most common types of automotive air-conditioning compressors.
Axial piston compressor
Tech A says that R-134a replaced R-12 as an approved refrigerant. Tech B says that HFO-1234yf refrigerant is flammable. Who is correct?
Both A and B
Tech A states that if moisture enters the air-conditioning system, acid will be created. Tech B states that evacuating an air-conditioning system will boil moisture, which will be removed from the system as a gas. Who is correct?
Both A and B
Tech A states that the system should be flushed if the compressor came apart. Tech B states that the system should be flushed if the oil is contaminated. Who is correct?
Both A and B
The automotive air-conditioning cycle starts with the ______.
Compressor
Which is the most common source of abnormal noises in an air conditioner?
Compressor
As corrosion inhibitors break down over time, the solution of water and antifreeze will become ______ acidic.
More
The function of air-conditioning in the HVAC system is to _______.
Reduce the temperature and humidity inside the passenger compartment to a level that ensures passenger comfort
Tech A says that the evaporator is on the high side of the system. Tech B says that the condenser transfers heat to the atmosphere. Who is correct?
Tech B
Tech A says that when an air-conditioning system freezes up, the refrigerant freezes and stops the cooling process. Tech B says that when an air-conditioning system freezes up, the evaporator coils are covered with frozen water molecules that stop airflow across the coils, thus preventing cooling. Who is correct?
Tech B
Tech A states that the wider the gap on an air-conditioning clutch, the greater the ohm reading when checking the windings. Tech B states that the air-conditioning clutch is electromagnetically operated. Who is correct?
Tech B
Tech A states that when using pressurized nitrogen to locate a leak, an electronic sniffer should be used. Tech B states that electronic sniffers are used when the system has at least a minimal refrigerant charge. Who is correct?
Tech B
If the pressure gauges read low pressure on the high side, high pressure on the low side, or about equal pressures, what might it indicate?
The compressor is not working fully.
All of the following statements are true with respect to testing the air-conditioning system except:
The heater fan needs to be on the lowest speed.
Why is it important to take pictures while removing the heater core?
To make reassembly easier
On some electronic HVAC systems, the high-pressure switch or ________ sends a signal to the HVAC module, and the module reduces the output of a variable displacement compressor and/or turns off the compressor clutch by turning off the clutch relay.
Transducer
Hoses are not as strong as pipes and tend to be porous.
True
It takes more heat to evaporate a liquid than to freeze a liquid.
True
Most R-134a refrigerant systems use three O-rings in the male pipe to create a good seal.
True
The condenser fan is designed to pull or push air from in front of the vehicle through the condenser to remove heat and reduce the high side pressure of the vehicle's air-conditioning system.
True
Using a cylinder leakage tester and pressurizing each cylinder can help locate which cylinder has the combustion leak, due to either a blown head gasket or a cracked head.
True
Manipulating nature's law of ________ of liquids and gases is how the air-conditioner forces ambient passenger compartment air to become cool and less humid for the driver and passengers of the vehicle.
Vaporization and condensation
When should radiator coolant be caught and reused while replacing a radiator?
When the coolant is new.
There are two types of belt tensioners:
automatic and manual.
The A/C compressor clutch is engaged and disengaged by using:
electromagnetism
A refractometer is used to test:
the freeze protection of the coolant.
A solenoid-controlled fan clutch is controlled by:
the vehicle's power train control module (PCM).
The best way to remove hoses from heater cores is:
to slit them and peel them off.
Manufacturers use various cooling system configurations, but the basic concept is to _______.
transfer excessive heat from hotter to cooler environments
In the automotive climate control system, the ________ measures the temperature of the outside air.
Ambient air temperature sensor
The receiver filter drier is constructed with a mesh and ________ media.
Cloth filter
If the HVAC system is computer controlled, the HVAC check should be done after a performance test, as some codes will cause the computer to shut off the HVAC system to protect it.
False
Inspecting and testing system control cables and linkages usually will not be needed if the air-conditioner or heater is not delivering the proper temperature of air or is delivering airflow to a different mode than selected.
False
The air-conditioner is an open loop system.
False
The removal of a heater core is not an easy task, as it will always be necessary to pull the entire dash from the vehicle.
False
When pressure is raised on a gas, its temperature decreases.
False
When testing a vacuum servo, if vacuum is not able to be held on the hose supplying vacuum to the servo, it is not leaking and the problem lies beyond the line.
False
When testing an inoperative blower motor, if there is power (voltage) and ground present at the blower motor connector, then the blower motor is operating normally.
False
While commanding an HVAC blend or mode door to move, if no movement at all is found at the actuator, the technician should inspect for a broken or binding door by turning the door by hand.
False
The heater core is made from tubes that have thin metal ______ connected to them, which increase the surface area tremendously.
Fins
The air-conditioning system should be _______ if the compressor comes apart or if the desiccant bag breaks open.
Flushed
If the radiator fins are blocked by debris, you may need to remove the radiator to carefully clean the fins with a ________.
Garden hose
_____ is shininess on the surface of the belt, which comes in contact with the pulley.
Glazing
As the _____ rotates, it catches the coolant and flings it outward with centrifugal force.
Impeller
If you are going to change hydraulic brake fluid, besides eye protection, what PPE should you use?
Impervious gloves
The ________ allows you to measure temperatures without opening either the cooling system or A/C system.
Infrared thermometer
Many automotive manufacturers have added cabin air filters to the ______ side of the heating/air-conditioning box where fresh air enters the cabin.
Inlet
When testing the A/C compressor electrical circuit, removing the compressor electrical harness and checking the voltage at the terminals should display ________ with the A/C turned on.
Near-full battery voltage
_______ temperature coefficient thermistors are typically used in automotive HVAC applications.
Negative
Coolants based on which of these technologies contain a proprietary blend of corrosion inhibitors and are claimed to be compatible with most other types of coolant?
POAT
A _______ is used to determine what the high- and low-side pressures should be at a given outside temperature and humidity in a properly functioning system.
PT chart
What is the term used to describe the process of making an HVAC system perform to its maximum ability and comparing that to specifications?
Performance testing
_______ are installed on A/C lines to protect the system from damage if system pressures are too high or too low.
Pressure switches
Which of the following refrigerants uses mineral oil?
R-12
The site glass is still used on some automotive air-conditioning systems but should not be used with ________.
R-134a
The ________ is located between the condenser outlet and the TXV inlet.
Receiver filter drier
After the _______ process, the air-conditioning machine will deposit any oil removed during the process into a graduated container on the machine.
Reclaim
On hot days, the refrigerant pressures are high and the compressor needs an effective drive belt to prevent _______.
Slipping and excessive heat buildup around the clutch
This hose has become very weak and is in danger of ballooning or bursting:
Soft hose
The________ in a relay pulls the contacts apart, stopping the current flow to the controlled device and turning it off.
Spring.
Attached to the spinning shaft of the heating and ventilation system's blower motor is what is called the " ______ ", a plastic cage with fins to pull or push air.
Squirrel cage
Tech A says that some drive belts are of a stretch fit design and are not adjustable. Tech B says that automatic belt tensioners never wear out. Who is correct?
Tech A
Tech A says that there are a number of coolant types and each has its own life span. Tech B says that mixing of coolants is generally okay because all coolants use the same chemical base. Who is correct?
Tech A
Tech A says that there are a number of coolant types that each has its own life span. Tech B says that mixing of coolants is generally okay, as all coolants use the same chemical base. Who is correct?
Tech A
Tech A says that when replacing cooling system hoses, it may be best to slit the hose rather than trying to twist it off. Tech B says that cooling system hoses only need to be changed when they start leaking. Who is correct?
Tech A
Tech A says that when troubleshooting an automatic temperature-controlled A/C or heating problem, one of the first steps should be to check codes for any related faults. Tech B says that codes should only be consulted if you get stuck during diagnosis. Who is correct?
Tech A
When both the gauges of an air-conditioning system read low pressure, what might be the problem with the A/C?
The system may be low on refrigerant
_______ type automotive air-conditioning systems use a receiver filter drier to ensure that a pure liquid refrigerant is delivered to the restriction.
Thermal expansion valve (TXV)
The __________ regulates coolant flow to the radiator.
Thermostat
Choose the correct statement with respect to driers.
They absorb any moisture in the system.
Choose the correct statement with respect to pressure switches.
They are used to engage and disengage the compressor clutch.
A drain hose is connected to the evaporator housing and exits through the vehicle's firewall.
True
A ring worn by a technician can get caught on moving parts, breaking the finger bone or even ripping the finger out of the hand.
True
Always follow the filter manufacturer's directions when cutting the air-conditioning lines and installing the air-conditioning filter.
True
Because the air-conditioning condenser sits in the front of the vehicle, it is damaged quite often in wrecks or by debris flying off the road.
True
Before starting a repair or service task on the cooling system, allow sufficient time for the system to cool adequately before opening the pressurized system.
True
Before testing the air-conditioning system, let the system stabilize for a few minutes to allow the refrigerant to equalize and the temperatures to reach the proper level.
True
Changing the vacuum pump oil regularly will extend the life of the vacuum pump and make it reach maximum vacuum quicker.
True
Electrolysis is the reaction of different metals to an acid solution to produce electricity.
True
Failure to perform required maintenance will result in cooling system failure, which can lead to breakdowns and major engine damage.
True
If the HVAC evaporator housing drain tube becomes clogged with leaves or debris over time, the water will not be able to drain; it will stagnate and begin growing bacteria, creating an unpleasant odor.
True
If the refrigerant in a vehicle is contaminated by the wrong refrigerant or the wrong oil, then it is considered a hazardous waste and must be put in a separate recovery unit and disposed of according to state and local laws.
True
Many new vehicles are designed with HVAC systems that have built-in self-diagnostics.
True
On a refrigerant with a thermal expansion valve, the temperature at the evaporator outlet regulates the pressure in the bulb.
True
All of the following statements are true of a thermostat except:
When the engine is cold, the valve is open; when hot, the valve closes.
Charging a system is performed only after the A/C system has been evacuated and:
any oil is replaced.
Surge tanks:
are mounted at the highest point of the cooling system.
An overflow tank is used to:
catch coolant that is released by the radiator cap when the coolant heats up.
The purpose of the evaporator in the A/C system is to do all of the following EXCEPT:
cause conduction of heat through the blower motor.
Negative temperature coefficient (NTC) thermistors:
decrease resistance as they warm up.
Servos are devices designed to:
do work
The device that is attached to the radiator to help draw air through the entire radiator is called the:
fan shroud.
The surface area that dissipates heat is increased by the use of:
fins.
A borescope is used:
for examining internal passages for evidence of a coolant leak.
The components that are not designed to be flushed include all of the following EXCEPT:
high side line.
When removing a radiator:
inspect the cooling system hoses and clamps.
When pressurizing coolant:
its boiling point increases.
When testing the cooling system for leaks using a pressure tester:
look for both internal and external leaks.
The engine's operating temperature can be verified using all of the following except a:
refractometer.
The surge tank:
removes gas from the system.
When removing the dash panels and covers for replacing a heater core, it is advisable to collect the ________ in a magnetic tray.
screws
The best way to remove coolant hoses is to:
slit them and carefully peel them off if they are stuck.
When diagnosing an HVAC system, it is a good idea to first check for common failures by checking:
technical service bulletins.
If the gauges of an air-conditioning system read low pressure on the high side, high pressure on the low side, or about equal pressures, it usually means that:
the compressor is not working.
Draining and refilling the coolant is necessary in all of the following cases except when:
the coolant level is low.
In case of reusing the old radiator coolant, ________.
the coolant should be stored in an uncontaminated container
The liquid with the best available cooling properties because of its ability to absorb large amounts of heat is:
water.
Thermostats use a ________ to open the valve to allow coolant flow.
wax pellet
Tech A states that an air-conditioning performance test usually requires that an auxiliary condenser fan be used during the test. Tech B states that a performance test will show if the air-conditioning system is contaminated with sealer. Who is correct?
Tech A
Tech A states that microns are a much more accurate unit of measuring vacuum than inches of mercury (Hg). Tech B states that microns are a much more accurate measure of time than seconds. Who is correct?
Tech A
Tech A states that to determine how much refrigerant is needed in a system, you must refer to identifying labels on the vehicle or the service information. Tech B states that to determine the amount of refrigerant needed, you just charge the system until the pressures look correct. Who is correct?
Tech A
Tech A says that coolant leaking out of the water pump weep hole means the pump is operating normally. Tech B says that the water pump uses centrifugal force to circulate coolant. Who is correct?
Tech B
If it is a serpentine belt system, the pulley edges should be within _______ of alignment with each other.
1/16"
Tech A says that conduction is when heat transfers through solids. Tech B says that radiation is when heat travels through space. Who is correct?
Both A and B
Tech A states that when evacuating an air-conditioning system, the vacuum should be maintained for approximately 10-15 minutes (but as long as 30 minutes) after the system reaches the boiling point pressure of water. Tech B states that one main purpose of evacuating an air-conditioning system is to remove any moisture from the system. Who is correct?
Both A and B
When removing the heater core, how should the heater hoses be removed?
By slitting the hoses lengthwise
Which hose allows the water pump to circulate the water in the engine when the thermostat is closed, but not when it is open.
Bypass hose
Which of the following components provides the needed refrigerant movement in the system?
Compressor
The 609 license ensures that the technician knows how to repair the automotive air-conditioning systems.
False
If the vehicle only overheats while stopped, it could be an issue with the ______, which directs airflow through the radiator.
Fan shroud
Which of the following is a clamp that can be adjusted using a nut driver?
Gear clamp
Tech A says that automotive air-conditioning is regulated by the EPA. Tech B says that EPA tests air-conditioning systems every five years. Who is correct?
Tech A
Tech A says that the design of a surge tank system helps to purge air from the cooling system. Tech B says that the overflow tank adds coolant to the radiator when the engine is hotter than normal. Who is correct?
Tech A
Tech A states that when removing any component of an air-conditioning system, the oil should be drained from it and measured so that the same amount of new oil can be reinstalled. Tech B states that oil should only be in the compressor, and if any oil is found in any other components, it means that the receiver drier is faulty. Who is correct?
Tech A
Tech A says that heat is removed from the passenger compartment by the heater core. Tech B says that heat in the cab is absorbed by the refrigerant and is transferred to the outside air at the condenser. Who is correct?
Tech B
When charging an air-conditioning system, if the pressure reaches a positive pressure number too rapidly, what does it indicate?
The reed valves in the compressor are likely bad.
When inspecting the ________ , clean any gasket material from the mating surfaces.
Thermostat housing
Both POE and PAG oils absorb moisture.
True
Coolant pH testing can be accomplished with test strips that turn color based on the level of acidity in the coolant, or electronic testers that measure the pH of the coolant directly can be used.
True
High pressures and low pressures can cause severe damage to air-conditioning system components.
True
The fixed orifice tube is used for:
allowing only a specific amount of liquid refrigerant through at a time.
The purpose of the A/C compressor is to:
change a low-pressure gas refrigerant to a high-pressure gas refrigerant.
Starting at the compressor, a low-pressure gas is compressed into a high-pressure gas and is pumped into the:
condenser.
The A/C condenser is normally positioned:
in front of the radiator.
The two common types of restrictions used in the A/C system are the fixed orifice tube and the:
thermal expansion valve.
It is necessary to remove and replace a thermostat in all of the following situations EXCEPT:
when the thermostat has been in use for a long time.
A sun load sensor is a:
photodiode.
Fixed orifice tube automotive air-conditioning systems use a(n) ______ to ensure that a pure gas is delivered to the compressor.
Accumulator
The ECU sends output commands to which type of component to control fan speed, heater core coolant flow, air-conditioning clutch activation, and so on?
Actuator
The first step in the diagnostic process of the HVAC system is _______.
Carrying out a performance test of the air-conditioning system
If voltages are over _____ volts when the load or loads are activated, then you will have to perform electrical diagnosis of the circuit being tested.
0.3
If the oil removed during the air-conditioning system reclaiming process was more than _______, the air-conditioning system needs to be flushed, and a base charge of oil needs to be established.
1 ounce
A performance test typically consists of turning on the air-conditioner to its maximum setting with the windows closed and raising the engine revolutions per minute (rpm) to _______.
1,200 - 2,000
In a serpentine belt system, the pulley edges should be within ________ of alignment with each other.
1.6 mm
When the micron gauge reaches ______ microns, the A/C system is moisture free.
1000
The cabin air filter should be inspected during every service and replaced according to the manufacturer's specified interval, typically every ________.
12,000 to 15,000 miles
During an A/C system performance test, what should the engine rpm be raised too?
1200-2000 rpm
What is the minimum amount of time an A/C system should be evacuated for to effectively boil all the water out of the A/C system?
15 Minutes
The ideal operating temperature for modern engines is:
200°F
Raising the pressure of water 1 psi (7 kPa) raises the boiling point of water approximately _____°F.
3
The typical electrical resistance for an automotive A/C compressor's electrical portion of the A/C clutch should be:
3 - 5 ohms.
For each "pound" (psi) of pressure applied to the cooling system, the coolant's boiling point is increased by:
3.0°F.
Approximately what percentage of heat energy is wasted by the cooling system, which prevents overheating of the engine components?
33%
The optimum vent temperature for a properly functioning A/C system is from:
38°F to 48°F.
How much is the boiling point of coolant increased when using a 13- to 15-psi radiator cap?
39-45°F
The average air flow through the vents should be an average of approximately:
800 fpm.
What percentage of the coolant in the system should be drained to avoid spills while replacing the thermostat?
50%
The normal mixture of the antifreeze and water that make up coolant is:
50/50.
Automotive air-conditioning service and repair technicians need to have which special license?
609 license
Extremely high-pressure readings on the high side indicate that there is ________.
A blockage on the high side or an airflow restriction across the condenser
Choose the correct statement.
A bottomed out belt will slip and squeal.
This easy-to-use device connects to the low-side air-conditioning fitting and takes a reading of the refrigerant.
A refrigerant identifier
Choose the correct statement.
A refrigerant identifier is used to determine the type of refrigerant.
What is the most common air-conditioning complaint that brings vehicles into the shop?
Air conditioner not performing
Most modern hybrids now use a high-voltage electric motor, which directly drives the ________.
Air-conditioning compressor
Overheating conditions can have several causes, such as a _______, clogged radiator tubes or fins, an inoperative cooling fan, a water pump impeller that is eroded or slipping on the shaft, or a blown head gasket, to name a few.
All of the above
Which of these faults can be diagnosed by using a DMM and referring to the wiring diagram to locate the fault?
All of the above (a bad fuse or motor, a faulty brush in the motor
A liquid-cooled system uses coolant, a fluid that contains _______.
All of the above (antifreezing chemicals, anticorrosion chemicals, water)
Heat transfer can take place by _______.
All of the above (conduction, convection, radiation)
If the air-conditioner or heater is not delivering the proper temperature of air, it can mean that a cable _______.
All of the above (is binding, is broken, has popped off its linkage at the door or control head)
Adapters are used to connect the tester to the __________.
All of the above (radiator, surge tank, radiator cap)
The under hood A/C sticker should detail:
All of the answers listed (A/C system oil capacity, A/C system charge amount, type of refrigerant to use)
This type of clamp is adjustable with a screwdriver:
All the answers listed (gear clamp, worm clamp, screw clamp)
In systems where the cabin air filter is in the fresh air intake, you can use a(n) ______ to check the difference in the speed of the vent airflow with the system in recirculation mode compared to fresh air mode.
Anemometer
_______ measure the velocity of the air in FPM.
Anemometers
The radiator hoses are held in position by _____.
Any of the above (v-belt, serpentine belt, multigroove belt)
In most machines, the vacuum pump is located ________.
Behind a cover inside of the air-conditioning machine
Make sure the clamps are installed just ________ the flared or barbed segment.
Beyond
Which of the following control a relatively large current flow in one part of a circuit by a much smaller current flow?
Blower motor speed controls
Mineral oil is clear to light yellow, and PAG oil is usually a light ________ color.
Blue
Allowing sealant to be drawn into a(n) _______ can ruin it.
Both A and B
As the acid level builds, so will _____ in the cooling system.
Both A and B
Perform a pulley alignment check as part of inspecting the drive belt system if ________.
Both A and B
Tech A says that if the air gap between the compressor clutch and the pulley is too large, the clutch may not engage. Tech B says that if system voltage is too low, the compressor clutch will not engage. Who is correct?
Both A and B
Tech A says that one advantage of an air conditioner is that the system removes water from the air. Tech B says that an AC compressor clutch is activated by a magnetic field. Who is correct?
Both A and B
Tech A says that the engine operating temperature can be tested with an infrared temp gun. Tech B says that it can be tested with a scan tool. Who is correct?
Both A and B
Tech A says that the radiator cap should be pressure tested as part of a cooling system diagnosis. Tech B says that the water pump weep hole could be the source of a coolant leak. Who is correct?
Both A and B
Tech A says that the thermostat may have an air bleed that must be positioned properly when the thermostat is replaced. Tech B says that the thermostat housing must be flush against the mating surface or the ear may break off when tightening the bolts. Who is correct?
Both A and B
Tech A says that when you find coolant hoses collapsed after the engine cools down, the radiator pressure cap has likely failed. Tech B says that the thermostat may have a bleed valve that should be accurately positioned when the thermostat is replaced. Who is correct?
Both A and B
Tech A states that pushing the windshield defrost button sends an "on" 12-volt signal to the ECU. Tech B states that pushing the floor button cancels the defrost button. Who is correct?
Both A and B
Tech A states that regular maintenance prompts may appear as you use the air-conditioning machine. Tech B states that vacuum pump oil can be changed by the shop technician. Who is correct?
Both A and B
Tech A states that the ECU of the HVAC system can receive a 12 volt signal. Tech B states that the HVAC ECU determines when to turn on the HVAC compressor. Who is correct?
Both A and B
Tech A states that with dual-zone temperature controls, the air box must have two blend doors and two blend door actuators. Tech B states that the dual-zone temperature control panel contains the same buttons used in other systems but has two temperature control switches. Who is correct?
Both A and B
Technician A says that the A/C compressor clutch is typically controlled by a relay. Technician B says the condenser fan is typically controlled by a relay. Who is correct?
Both A and B
Technician A says that the number-one failure leading to mechanical breakdown for motorists is cooling system failure. Technician B says that a failing cooling system can affect engine emissions and fuel economy. Who is correct?
Both A and B
Technician A states that after a new heater core is installed, the air box removal steps should be reversed to reinstall the air box. Technician B states that after reinstalling the air box, the cooling system should be refilled. Who is correct?
Both A and B
Two technicians are discussing cooling system hose replacement. Tech A says to make sure that the hose clamps get installed just inside the flared or barbed segment of the fitting, not on top of it. Tech B says that it is good practice to install new hose clamps at the same time as new hoses. Who is correct?
Both A and B
Vacuum servos can fail by not pulling ________.
Both A and B
Coolant should never be dumped _______.
Both A and B (into a storm drain, down a shop floor drain)
When replacing the radiator, make sure the coolant catch tray ________.
Both A and B (is large enough to catch any spills, has the capacity to hold all the system coolant)
One should never try to inspect belts when the engine is _________.
Both A and C (cranking, running)
The rotor housing has _______ cast and machined into it, which go around the rotor housing and allow heat to be pulled from around the rotor where combustion is taking place.
Both B and C (water jackets, passageways)
Technician A says that when using a jumper wire to be sure to use a fused jumper wire. Technician B says that if a fused jumper wire is hooked up incorrectly it can still damage vehicle electronic components. Who is correct?
Both Technician A and Technician B
Heat energy is measured in _______.
British thermal units
How does air-conditioning absorb a large amount of heat energy?
By evaporating a liquid
The ________ temperature sensor is a valuable input to the climate control system's ECU to ensure that it knows what the temperature is so it can cause the actuators to respond appropriately.
Cabin air temperature sensor
________ is the process of transferring heat through matter by the movement of heat energy through solids from one particle to another.
Conduction
Leaks from the heater core can result in _____ misting out of the vents or dripping onto the passenger-side carpet.
Coolant
Removal of a heater core may become necessary if the customer notices a puddle of ________ on the carpet in the vehicle, usually on the passenger side.
Coolant
The heater control valve, if equipped, regulates ______ flow to the heater core.
Coolant
Performing a _______ can help determine whether to perform a radiator repair or to buy a new radiator.
Cost analysis
The air-conditioning box has a _____ that allows removal of water collected from the moist air as it condenses on the cold evaporator and drips into the box.
Drain tube
If the ______ of a compressor is worn, the engine may not be able to drive the compressor properly.
Drive belt
Technicians must be ________ certified to handle refrigerants.
EPA 609
Most vehicles use a ______ to control the amount of heat delivered to the passenger compartment.
Either A or B (blend door, heater control valve)
In ________ testing, R-134a passing by the diode is broken down, thereby creating an electrical current charge; the internal mechanics of the diode use this charge to determine how much refrigerant has passed.
Electronic sniffer
Which of the following sensors signals to the ECU the temperature of the coolant which flows through the heater core?
Engine coolant temperature sensor
When replacing a heater core, the air-conditioning refrigerant should be recovered if the ________ needs to be removed.
Evaporator
Which of the following components in the AC transforms low-pressure fluid to low-pressure gas?
Evaporator
Which of these is the most common issue a technician might encounter with the automatic HVAC system?
Failure of electric actuators
Additional filters installed in the HVAC system are designed to substitute for an adequate flush.
False
Anytime air-conditioning lines are loosened, the O-rings in the fittings must be reseated or there will be potential for leaks.
False
Heated coolant is pumped to a heater core where the blower causes air to flow through the heater core and the passenger compartment is cooled.
False
Heater control valves cannot leak coolant.
False
The ECU receives instructions regarding the desired cabin temperature from the:
HVAC control panel.
The ______ sniffer is considered the best sniffer available for R134a leak detection.
Heated diode
A good flush of the entire cooling system of a radiator will be necessary as further clogging will be likely, especially in the _________.
Heater core
All of the following statements with respect to hoses, pipes, and tubes are true except:
Heater hose can substitute for air-conditioning hose if needed.
To check a cabin air filter, remove it and ________ to see if it needs to be replaced.
Hold it up to a light
Why is heater core removal typically difficult?
It is usually necessary to pull the entire dash from the vehicle
All of the following are properties of a refrigerant except:
Its pressure remains unchanged during the cooling cycle.
_______ testing should be performed on every system that is low on refrigerant or has just been repaired.
Leak
The evaporator transforms refrigerant from a ________ in the air-conditioning system.
Liquid to a gas
To measure the current flow of a vehicle's blower motor, use a(n) _________.
Low-amp clamp (inductive clamp) around the wire to or from the motor
If the climate control system that is being worked on has a(n) ______ panel, there will be a rotary or linear switch for fan speed, a rotary or linear switch for modes (floor, defrost, vent, or vent and floor), and a rotary or linear switch for temperature.
Manual control
Tech A says that an accumulator creates the pressure needed for the air-conditioning system to operate. Tech B says that the high side refers to refrigerant entering the compressor. Who is correct?
Neither A nor B
Tech A says that an electric fan that runs all the time can cause the engine to overheat. Tech B says a refractometer is used to turn a clutch fan on and off. Who is correct?
Neither A nor B
Tech A says that the cooling system is designed to keep the engine as cool as possible. Tech B says that heat travels from cold objects to hot objects. Who is correct?
Neither A nor B
Tech A says that the engine thermostat controls the flow of coolant through the heater system. Tech B says that the heater core can have engine coolant or refrigerant flowing through it, depending on whether heat or cool is commanded. Who is correct?
Neither A nor B
Tech A says that when 100% antifreeze is used in the cooling system, the protection level is approximately -70°F. Tech B says that 100% antifreeze will cool the engine better than 100% water. Who is correct?
Neither A nor B
Tech A says that the air-conditioning compressor creates high-pressure liquid. Tech B says that the restriction creates a physical change in refrigerant from a liquid to a gas. Who is correct?
Neither A or B
Which of the following types of testing requires an empty air-conditioning system?
Nitrogen testing
The cooling system of the rotary engine is _______ the piston engine's cooling system.
Not much different from
If the clutch on the air-conditioning compressor does not engage, you will notice that the center of the compressor pulley (the front portion of the pulley) is ________.
Not turning
With ______, a belt that has been soaked in oil will not grip properly on the pulleys and will slip.
Oil contamination
When charging an A/C system from the high side only, when the charging begins, watch the low-side pressure gauge. If the low-side gauge does not reach zero before 10 seconds, the TXV or ______ is bad.
Orifice tube
A ______ can also tell the proportions of antifreeze and water in the coolant mix (or the level of freeze protection) by measuring a liquid's specific gravity.
Refractometer
________ control a relatively large current flow in one part of a circuit by a much smaller current flow.
Relays
The best way to make sure the air-conditioning system is properly charged is to _______.
Remove all refrigerant from the system and reinstall the proper amount of refrigerant
The state of charge in an A/C system is best tested by ______ and comparing the amount to manufacturers specified proper amount.
Removing the refrigerant
What should be the first step when diagnosing HVAC ECU systems?
Researching the manufacturer's diagnostic procedures and following the procedure relating to the symptoms present
What type of compressor uses two interwoven scrolls?
Sanden scroll-type compressor
A(n) ______ is necessary for checking DTCs in the ECU of the HVAC system and for performing bidirectional controls of electrical loads.
Scan tool
Use a ________ and compare the reading from the coolant temperature sensor to the temperature gun reading to verify that the PCM is receiving the correct temperature signal.
Scan tool
Before you begin to identify a refrigerant, you first need to make sure there is no ______ in the system.
Sealer
A(n) ________ HVAC system uses an ECU to determine when to run the compressor and the amount of heat required to match and maintain the desired temperature selected by the operator.
Semi-automatic
Which of these systems is able to control the air doors and fan speed to match the climate inside the vehicle to the settings selected?
Semiautomatic
The resistor pack or resistor block uses resistors in _______ to regulate the speed of the blower motor fan.
Series
A spring-loaded automatic tensioner is typically used with ________.
Serpentine accessory belts
Remove the engine drive belt using a(n) _______.
Serpentine belt tool
When cleaning the condenser to remove debris, _______ may be used to remove the debris, but be careful to not fold over the fins.
Shop air or a water hose
If the ____ is missing, air will be pulled from around the fan blades rather than through the radiator.
Shroud
Tech A says some newer vehicles use pulse width modulation (duty cycle) to control blower motor speeds, which leads to smooth changes in speeds. Tech B says that the evaporator temperature sensor is used to measure the temperature in the passenger compartment. Who is correct?
Tech A
Tech A says that coolant leaks can be located by performing a pressure test on the system. Tech B says that when pressure testing the cooling system, you should pressurize it to at least 10 psi (69 kPa) above the radiator cap pressure rating. Who is correct?
Tech A
Tech A says that raising the pressure on the cooling system raises the boiling point of the coolant. Tech B says that air-cooled engines operate within a more consistent and ideal temperature range. Who is correct?
Tech A
Tech A states that refrigerant in a vehicle should be identified before recovering the refrigerant. Tech B states that refrigerant doesn't need to be identified if you are only topping up a system with refrigerant. Who is correct?
Tech A
Tech A says that air flow in the vents is controlled by adding or removing a second or third motor to increase or decrease air flow. Tech B says that blower motor speed is controlled by controlling voltage and current to make the blower motor run faster or slower. Who is correct?
Tech B
Tech A says that electric cooling fans are used to cause a large airflow over the radiator when the engine is cold. Tech B says that electric cooling fans are used to cause a large airflow over the radiator at low vehicle speeds. Who is correct?
Tech B
Tech A says that in a temperature blend air system, the air conditioner runs continuously. Tech B says that in a temperature blend air system, heated coolant always flows in the heater core. Who is correct?
Tech B
Tech A says that most coolants are designed to last the life of the vehicle. Tech B says that a hydrometer can be used to test the freeze point of coolant. Who is correct?
Tech B
Tech A says that most hybrids now use a high-voltage electric motor that directly drives the A/C compressor. Tech B says that some hybrids use dual-drive air-conditioning compressors. Who is correct?
Tech B
Tech A says that one coolant test is a coolant electrolysis test. Tech B says that a thermostat that is stuck open will cause the engine to run cooler than it should. Who is correct?
Tech B
Tech A says that some electric actuators are positioned by an A/C ECU which checks the air flow with sensors. Tech B says that electric actuators are positioned by an A/C ECU and some actuators have a potentiometer to tell the A/C ECU the position of the door. Who is correct?
Tech B
Tech A says that the fresh air setting pulls air from the cabin. Tech B says that when the outside temperature is very hot, the recirculate setting will cool the cabin further. Who is correct?
Tech B
Tech A says that the thermostat is open until the engine warms up, and then it closes. Tech B says that a faulty radiator cap can be the cause of boiling coolant. Who is correct?
Tech B
Technician A says that testing using Voltage drop is ineffective in the diagnosis of blower motor function. Technician B says that using a DMM can be helpful in diagnosing a faulty blower motor. Who is correct?
Tech B
Technician A says that coolant leaks can be located by performing a pressure test on the system. Technician B says that when pressure testing the cooling system, you should pressurize it to at least 10 psi (69 kPa) above the radiator cap pressure rating. Who is correct?
Technician A
Technician A says that in most cases even if a job requires a full face shield, it is typically an accepted practice to wear just safety glasses. Technician B says you need to make sure the PPE you are using is worn correctly. . Who is correct?
Technician B
Technician A says the bypass hose is used to regulate cooling system pressure. Technician B says that radiator hoses should be checked during routine maintenance. Who is correct?
Technician B
Technician A states that all thermostats are equipped with an air bleed valve. Technician B states thermostats may or may not be equipped with an air bleed valve. Who is correct?
Technician B
The evaporator _______ sensor ensures that the evaporator temperature does not get too cold.
Temperature
To check the operation of automatic or semiautomatic HVAC control systems, the service information also usually provides you with _______ charts to which you can compare your results.
Temperature
Section 609 of ______ the federal law that regulates air emissions from stationary and mobile sources contains all of the motor vehicle air-conditioning (MVAC) requirements and laws.
The Clean Air Act (CAA)
In a typical orifice tube system, which of the following indicates an undercharge of refrigerant?
The air-conditioning clutch has a rapid cycle time.
All of the following can cause the compressor clutch to not engage except:
The clutch coil receives full power and ground.
On occasion, the problem of not blowing cold air is not the air-conditioning system at all; rather, the blend door or heater control valve is not closing adequately to keep air or hot coolant from passing through the heater core.
True
Once the dash is removed, the air-conditioning evaporator box is unbolted from the vehicle, and then the case can be split open by removing more screws to access the evaporator.
True
Pressure switches, whether high or low, will have a cutoff pressure to protect the air-conditioning system.
True
Some vehicles require auxiliary airflow provided by an external condenser fan.
True
The 609 license never expires.
True
The PCM may shut down the air-conditioning system if there is a charging system problem or an overheating issue and the PCM determines that the extra load on the engine created by the air-conditioning needs to be shut down until the other problem is resolved.
True
The air gap of an automotive air-conditioning compressor is the space between the clutch assembly and the air-conditioning pulley.
True
The air-conditioning reclaim/recovery machine can measure the amount of refrigerant recovered from the vehicle.
True
The coolant level should not be below the lower mark when the vehicle is cold.
True
The fixed orifice tube air-conditioning system is less efficient than the TXV system.
True
The hottest part of any engine is the cylinder head because this is where the combustion chamber is located.
True
The orifice tube should be replaced if the compressor comes apart internally because it can catch debris from the compressor and become clogged.
True
The pressure tester puts pressure on the cooling system, and with pressure applied, leaks generally show up easily, as identified by coolant coming from the source.
True
The sensor for either type of warning device sits in engine coolant so that an accurate reading is always given that is, as long as the coolant is not low.
True
To inspect a vehicle's cabin air filter, remove the cabin air filter and hold it up to a light to see if it is restricted.
True
When an HVAC system is overcharged, both the low- and the high-side gauges will be running higher than normal.
True
When coolant enters the center of the water pump and the internal rotor spins, centrifugal force moves the liquid outward toward the outlet.
True
When inspecting the cabin air filter, you should use the same guidelines as for an engine air filter.
True
When using leak dye for the first time on an air-conditioning system, the dye needs to be injected as a concentrate into the system.
True
When working with the expansion valve, caution must be used in all aspects of the removal and installation of the valve.
True
With use of a recovery system, no coolant is lost and excess air is kept out of the system.
True
You should replace the amount of oil that was removed during the reclaim process if it was less than 1 ounce.
True
If a vehicle uses ________ servos to control the HVAC mode doors and blend door, failure in the vacuum hose(s) can result in failed operation.
Vacuum
After coolant moves through the ______, it finds its way to the thermostat, where it returns to the radiator.
Water jackets
Which of these is used to force coolant throughout the cooling system in order to transfer heat energy?
Water pump
This spring clamp is not adjustable:
Wire clamp
A jammed blower motor fan could result in:
a blown blower motor fuse.
When there is a difference in the speed of the vent airflow with the system in recirculation mode compared to fresh air mode, may indicate:
a jammed fan.
If refrigerant leaks out of the A/C system, the low-pressure switch opens to protect the system from:
a lack of lubricant.
Desiccant is used in the receiver drier to:
absorb moisture in the system.
Desiccant failures arise when the system is left open for long periods of time and the desiccant:
absorbs too much moisture.
Resistors in series are sometimes used to control:
blower motor speed.
All of the following should be checked for coolant leaks when pressure testing a cooling system except:
clutch fan.
The most common component that will cause abnormal noises in the A/C system is the:
compressor
The job of the accumulator is to make sure that liquid refrigerant does not enter the:
compressor.
The type of heat transfer where heat is transferred from one solid to another is called:
conduction.
When the A/C machine alerts you that it needs service/repair, you should:
contact the local service department for the machine.
Heat is transferred through liquids by:
convection.
The liquid used for the cooling system is known as:
coolant.
If the vehicle only overheats while stopped, it is likely an issue with the:
cooling fan.
In an orifice tube style A/C system the A/C accumulator is located between the:
evaporator and the compressor.
After evacuating the system the technician should determine how much oil to put back in the system by:
measuring the oil removed.
Vacuum pumps are rated in the total volume of air that can be removed every:
minute.
The A/C system is a sealed system that:
must not leak.
Clocking means:
noting the routing of the hose so it can be reinstalled correctly.
The purpose of refrigerant going through a restriction is to change all of these refrigerant characteristics EXCEPT:
pH balance.
The position of the servo motor can be reported back to the ECU by use of a:
potentiometer.
The coolant heat storage system:
preheats the engine when the vehicle is started the next time.
The cooling system device that maintains pressure in order to raise the boiling point of the coolant is called the:
pressure cap.
Leak testing can be done by any of the following methods EXCEPT:
pressure testing.
The movement of heat through space is known as:
radiation.
The cooling system component that transfers the heat from the coolant to the air is called the:
radiator.
Removing refrigerant from a system is known as reclaiming or:
recovering.
A coolant serves all of the following purposes except:
reducing friction in the moving parts of the engine.
The engine's operating temperature can be verified using all of the following EXCEPT a:
refractometer