26 Automobile AC

As the engine speed decreases, the cooling capacity of the car AC system

• increases
• Remains unchanged
• Decreases
• May increase or decrease depending on number of persons travelling in car

Explanation:

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The AC of a car Air-conditioning system can be regarded as ……….

• DX system (Direct expansion)
• Indirect expansion system
• Both direct and indirect expansion
• Neither direct nor indirect expansion

Explanation:

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What is measured by a gauge manifold in automobile air conditioner?

• Evaporator pressure only
• Condenser pressure only
• Both mass flow and refrigerating effect
• Both evaporator and condenser pressure

Explanation:

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A manifold set has two gauges, blue and red. The blue is for low pressure and red is for high pressure. ……… of car air conditioner allows a full range of blower speeds from full, fast, too slow?

• Magnetic clutch
• Thermostat
• Fuse
• Rheostat

Explanation:

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What is the purpose of adding dye to the car A.C. system?

• Shine the car
• Lubricate the engine
• Adding performance
• Identify the gas leak

Explanation:

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Air refrigeration cycle is used in-

• domestic refrigerator
• aircraft refrigeration system
• commercial refrigerator
• all of these

Explanation:

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The manually cleaned type of filter has no-

• plastic frame
• metal frame
• cloth frame
• none of these

Explanation:

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The ………… of oil can be properly controlled by the force feed lubrication.

• distribution
• travel
• speed
• flow

Explanation:

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The cooling system used in air-craft cooling is-

• vapor compression system
• vapor absorption system
• air cycle refrigeration system
• steam jet refrigeration system

Explanation:

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The purpose of automobile air-conditioning is to produce comfort in the passenger chamber by controlling for fo

• temperature and pressure
• temperature and humidity
• humidity and pressure
• temperature, humidity and pressure

Explanation:

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From which component is the compressor of car AC connected to?

• From the radiator of car
• From the engine of car
• From the wiper of car
• None of the above

Explanation:

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The free wheeling technique is used in car AC System-

• evaporator
• compressor
• condenser
• receiver

Explanation:

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The key points in maintenance of car AC is-

• make sure to use the car AC at least once in a week
• operate the car AC on defrost mode to protect it from moisture
• flush the radiator of car AC at fixed time period
• all of these

Explanation:

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The component will two members used to save energy in a car AC is-

• magnetic clutch
• free wheeling
• drier
• evaporator

Explanation:

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Why is the car AC operated in winter?

• To control the temperature of the car
• To reduce the humidity inside the cabin of a car
• To control the air in the carr
• All of these

Explanation:

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The possible causes failure of car AC is-

• loose belt
• magnetic clutch is not pressed properly
• thermostat valve is not functioning
• tight connection of AC

Explanation:

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The condenser used in a car AC is generally made of which metal?

• Silver
• Copper
• Aluminium
• Tin

Explanation:

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Which lubrication oil is recommended for R-134A car AC system?

• Automobile oil
• Mineral oil
• Camphor oil
• POE oil

Explanation:

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The compressor of the car Air-conditioning system gets the drive from-

• solar panels
• car battery
• generator car
• I.C. engine

Explanation:

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The condenser of a car AC is-

• water cooled
• air cooled
• evaporative type
• none of these

Explanation:

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The upcoming alternative refrigerant to be used in car air-conditioning system is-

• R134a
• R1234yf
• R1234ze
• R764

Explanation:

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Where is the AC located in the car?

• At the rear side
• In the front side
• On the roof
• All of these

Explanation:

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The component used to trigger compressor in a car AC is-

• magnetic clutch
• condenser
• evaporator
• air filter

Explanation:

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Where is the thermostat fitted in car AC?

• Near the engine
• On the roof
• In the passenger compartment unit
• On back side

Explanation:

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Which of the following is controlled by car AC?

• Temperature
• Humidity
• Air cleanliness
• All of these

Explanation:

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The unit to measure the flow of air in car AC is-

• RPM
• KMH
• CFM
• PSI

Explanation:

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The part of electrical circuit of car AC is-

• compressor
• thermostat
• battery
• all of these

Explanation:

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Possible reason for less air flow in automobile A.C. is-

• ventilation fan not working
• air blower not working
• blocked air inlet port
• all of these

Explanation:

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Instead of air unit operating in automobile A.C. what could be probable reason of failure in cooling process?

• Thermostat not working
• Blockage in condenser
• Reduced refrigerant level
• All of these

Explanation:

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Where was the car A.C. used for the first time?

• USA
• China
• India
• France

Explanation:

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Where the battery negative terminal is connected in auto A.C.?

• A.C. relay
• Ground
• Blower motor
• Ignition switch

Explanation:

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Possible reasons of obtaining polluted air in car is-

• malfunction in air filter
• reduction in quantity of refrigerant
• leakage
• none of these

Explanation:

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Possible reason for less cooling in automobile A.C. is-

• malfunction in air filter
• reduction in quantity of refrigerant
• leakage
• both (b) and (c).

Explanation:

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Automobile A.C. depends on the following factor(s)

• speed of the car
• number of people sitting in the car
• both (a) and (b)
• none of these

Explanation:

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Components used in automobile A.C. is-

• compressor
• condenser
• evaporator
• all of these

Explanation:

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Which component, with respect to engine is used to control the compressor of car A.C.?

• Magnetic clutch
• Free wheeling
• Drier
• Expansion valve

Explanation:

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Fuel consumption in automobile A.C. can be reduced by-

• reducing the speed of the car
• increasing the speed of the car
• a lot of people are sitting
• all of these

Explanation:

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In which vehicle was the automobile A.C. first used?

• Car
• Bus
• Truck
• Train

Explanation:

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Which part of A.C. system is placed near automobile radiator?

• Evaporator
• Condenser
• Compressor
• Air blower

Explanation:

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At high speed of engine, AC system will generate-

• heat
• over cooling
• cooling
• none of these

Explanation:

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Automobile A.C. compressor is operated through-

• radiator
• engine
• wheels
• all of these

Explanation:

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Which components of A.C. are present near the engine of automobile A.C.?

• Condenser
• Compressor
• Both (a) and (b)
• Evaporator

Explanation:

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Which part of A.C. is installed near cabin of automobile?

• Condenser
• Compressor
• Both (a) and (b)
• Evaporator

Explanation:

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Which of the following is hot compressed refrigerant receives and cools it?

• Dehydrator
• Condenser
• Evaporator
• Throttle valve

Explanation:

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Which refrigerant in automotive air conditioning is used for?

• Ammonia
• Carbon dioxide
• Freon
• Brine

Explanation:

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Which of the following is a component of a refrigerant flows on a component, where it ANE completely receiver drier?

• Expansion valve
• Condenser
• Compressor
• Evaporator

Explanation:

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The chemical formula of freon used in automobile air conditioning is-

• \(CCl_2F_2\)
• \(CClF_2\)
• \(CCl_2F\)
• \(CClF\)

Explanation:

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3 ton capacity air conditioning equivalent to

• 9702 kcal/hr
• 9270 kcal/hr
• 7092 kcal/hr
• 9072 kcal/hr

Explanation:

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Which of the following removes the moisture particles present in the air conditioning system so that freezing of moisture does not occur at low temperature?

• Condenser
• Dehydrator
• Evaporator
• Expansion valve

Explanation:

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When refrigerant suddenly expands at very low pressure so what is the reason for this?

• Heating effect
• Cooling effect
• No effect
• Very little impact

Explanation:

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Conventional petrol by turning on the air conditioner fuel economy of the engine is approx. Decrease by 20% when you use the air conditioner in a hybrid gas-electric vehicle so what happens?

• It has almost the same effect
• There is less loss of gas mileage
• There is greater loss of gas mileage
• Has no effect on gas mileage

Explanation:

 

engine speed

• cooling capacity of the car AC system is influenced by the engine speed.
  • speed decreases, the cooling capacity Decreases.
  • Higher engine speed, higher the cooling capacity.
  • At high speed of engine, AC system will generate over cooling. 
• However, the increase of engine speed will also lead to increase in the input power of the compressor.

DX system

• The AC of a car Air-conditioning system can be regarded as  DX system (Direct expansion)
• In a DX cooling system, the evaporator is placed inside the spaced to be cooled.
• The refrigerants enters the DX cooling coils, where it absorbs the heat from the air and transforms to a gas. The refrigerant then move into the condenser located outside, where the heat is released.
•  Indirect expansion system

manifold | gauge

• A manifold gauge is a pressure checking system.
• A manifold gauge used in automobile air conditioning measure both evaporator and condenser pressure.

Magnetic clutch

• The magnetic clutch is an electromagnetic device that connects and disconnects the AC compressor from the engine’s power.
• Core Components: Consists of a stationary electromagnetic coil, a pulley (driven by the engine belt), and a pressure plate (fixed to the compressor shaft).
• Engagement Mechanism: When the AC is turned on, current flows through the coil, creating a magnetic field.
• Frictional Force: This field pulls the pressure plate into contact with the spinning pulley, forcing them to rotate as one unit.
• Power Transfer: Once engaged, engine torque is transferred through the belt to the compressor to begin the cooling cycle.
• Disengagement: Turning off the AC cuts the power to the coil; internal springs pull the plate back, allowing the pulley to freewheel without spinning the compressor.
• Cycling: It frequently engages and disengages (cycles) to maintain consistent cabin temperature and prevent the evaporator from freezing.
• Air Gap: A precise “air gap” (usually 0.4 mm to 0.8 mm) is required between the pulley and plate for proper operation.
• Common Failures: Burnt coils, worn-out friction surfaces, or a seized bearing can cause the AC to stop cooling or create loud squealing noises.

Fuse

• Acts as a sacrificial link that breaks the circuit if the electrical current exceeds safe levels, preventing wiring fires or component damage.
• Primarily shields the AC compressor clutch, blower motor, and cooling fans.

Thermostat

• The thermostat fitted in the passenger compartment unit in a car AC.
• In most cars the thermostat is placed under a housing near the water pump on the cylinder head. 

blower

Rheostat

• Rheostat of car air conditioner allows a full range of blower speeds from full, fast, too slow.
• A rheostat is an electrical component that can be used to adjust the resistance in circuit.
• This can be used to control the amount of current flowing through the circuit or to vary the voltage across a component.
• Rheostats are commonly used
  • to control the brightness of lights
  • the speed of motors 
  • the volume of audio equipments.

dye

• Purpose of adding dye to the car AC system is identify the gas leak.

Air refrigeration cycle

• Air refrigeration cycle is used  in aircraft refrigeration system.
• Air refrigeration system works on the joule cyclé or reverse brayton cycle or Bell-Coleman cycle.
• In this cycle, working medium is gas (air).
•  Air refrigeration cycle is favorable for aircraft refrigeration system, because-
  • (i) The gas does not undergo any phase change during the cycle.
  • (ii) Air is non-flammable, so there is no risk of fire.
  • (iii) Cheaper and easily available.

filter

• The manually cleaned type of filter has metal frame.

feed lubrication | Pressure lubrication system

• The distribution of oil can be properly controlled by the force feed lubrication.
• For feed lubrication/Pressure lubrication system :  The pressure created by an oil pump for force feed lubrication system in the engine.
• Distribution of oil can be properly controlled by the force feed lubrication.
• This system is commonly used on the high-speed multi-cylinder engine in tractors, trucks, and automobiles.
•  The cooling system used in aircraft cooling is vapour compression system. Air cooled system- In an air-cooled system a current of air made to flow past two outside of the cylinder barrel, the outer surface area of which has been consider by increased by providing cooling fines. This method is mainly applicable to general aviation aircraft, lower motors generators pump sets and motorcycles.
• The purpose of automobile air conditioning is to produce comfort in the passenger chamber by controlling temperature and pressure. 11. Air conditioning refers to any from of technological cooling, heating, ventilation, and disinfection that modifies the condition of air. 
• The refrigerant absorbs the heat of the air flowing into the passenger compartment and turns back into gas at the evaporator, it is then drawn in again by the compressor, where it is compressed the compressor is attached to the engine block and is driven by a pulley and V-belt.
• The key points in maintenance of car AC is- Make sure to use the car AC at least once in a week. Operate the car AC on defrost mode to protect it from moisture. • • Flush the radiator of car AC at fixed time period. Run your AC weekly on defrost mode you should run your air conditioning weekly for 10 minutes on defrost mode on the coolest setting and at the maximum fan speed. Clean or change the air filter.
• The component will two members used to save energy in a car AC is free wheeling.
• The car AC operate in winter to reduce the humidity inside the cabin of a car. Inside the car the temperature is quite warm and comfortable, as people tend to keep the windows up.
• The possible cause failure of car AC is loose belt, it may be due to a lack of refrigerant, a clogged expansion tube or refrigerant charging hose, a broken compressor, broken blower motor, damaged condenser or evaporator.
• POE lubrication oil is recommended for R- 134A car AC system.
• The condenser is heat exchanger, it is located at the front of the vehicle. The condenser cools down the refrigerant heated up by the compressor, and becomes a liquid (condensates) by transferring its heat to the flow of ambient air passing through it.
• R-134a has been the dominant refrigerant since the phase-out of R-12 but R-1234yf and CO2 (R- 744) are emerging as sustainable alternatives.
• AC is attached to the front of the engine and powered by a belt and pulley. It can be at the top or down along the side of the engine.
• Air conditioning is the simultaneous control of the temperature of the air, the velocity of air, purity of air, and humidity of the air.  It is the process of altering the properties of air to move favorable conditions.
• Cubic feet per minute (CFM) is a measurement of airflow volume, determined by how many cubic feet of air pass by a stationary point in one minute. 
• Possible reason for less air flow in automobile A.C. is- Ventilation fan not working Air blower not working Blocked air inlet port – Excess moister in your evaporator core can lead to the buildup of mold and other debris that block air flow to the cabin. 
• It instead of air unit operating in automobile AC is thermostat not working and blockage in condenser could be probable reason of failure in cooling process.
• A company in New york city in the United States first offered the installation of air conditioning for cars in 1993 most of their customer operated limousines and luxury cars.
• The first starting and charging system were designed to be 6-volt and positive ground system, with the vehicle’s chasis directly connected to the positive battery terminal. Today, almost all road vehicles have a negative ground system. The negative battery terminal is connected to the car’s chasis.
• The air that is circulating inside the cabin of your vehicle may include pollutants from different type of sources the outdoor air, the vehicle it self, malfunction in air filter and the occupants.
• Automobile AC depends on number of people sitting in the car and speed of the car.
• The components of a car AC system- • Expansion valve Evaporator Orifice tube Receiver drier AC inliers filter AC refrigerant.
• As you switch on the AC system, an electromagnetic clutch sets the belt drive in motion. The swash plate oscillates six double ended pistons that are responsible for intake as well a compression. Not that amount of refrigerant flow is controlled by reed valves.
• While all this seen like a minor issue getting it wrong can have a notable impact on your fuel economy using AC can increase your fuel consumption by as much as 10%. But opening the windows at higher speed can increase fuel consumption by as much as 120%.
• The 1953 Chrysler Imperial was one of the first production cars in twelve year to after modern automobile air conditioning as an option, following tentative experiments by Packard in 1940 and Cadillac 1941.
• Condenser- Vehicles AC condenser is usually located in the front of the radiator, giving it the nickname of the mini-radiator.

Expansion valve

• Refrigerant flow from the receiver drier to one of the components, where it expands suddenly and its pressure becomes very low, that components is the expansion valve.
• Expansion valve – The refrigerant flow from the receiver drier to the expansion valve where it suddenly expands to a very low pressure and the refrigerant turns into vapor and causes a cooling effect.

freon

• The chemical formula of freon used in automobile air conditioning (CC12F2) is Di-chloro-difluoro-methane.
• Freon is used extensively as a refrigerant in automotive air conditioning.
• Freon- Freon is a type of gas,  when the compressor if it is pressed, the temperature of this gas increases.
• The main device of freon is the compressor which move it. By removing gas heat from high pressure freon this liquid gets changed.

ton of refrigeration

• A ton of refrigeration (TR) is a unit of heat extraction capacity of the refrigeration or cooling equipment.
  • 1 TR  = 3.5 kw = 12000 BTU = 3024 kcal/hr

Condenser | condenser

• Most car AC system have five essential parts-
  • Compressor
  • condenser
  • evaporator
  • receiver drier
  • expansion tube- some vehicle may have an orifice tube instead of an expansion tube. 
• The condenser used in a car AC is generally made of aluminium. 
• Condenser is a type of fin and radiator.
• The condenser is installed in the front of the car’s radiator.
• The condenser receives the heated and compressed steam from the compressor.
• After this the refrigerant is in the form of high pressure liquid, which is fed into the receiver drier unit.

Evaporator | evaporator

• Evaporator is the part of AC that is installed near cabin of automobile. 

compressor

• AC compressor are driven by an engine accessory belt.
  • If the belt is worn and steps the compressor won’t operate at full strength.
• The free wheeling technique is used in car AC system compressor.
• The compressor of the car air-conditioning system gets the drive from IC engine. 
  The component used to trigger compressor in a car AC is magnetic clutch.
• part of electrical circuit of car AC
  • compressor
  • thermostat
  • battery
• Possible reason for less cooling in automobile AC is
  • AC refrigerant leak
  • Condenser blocked
  • Damaged compressor belt
  • Reduction in quantity of refrigerant

Dehydrator | dehydrator

• Dehydrator removes the moisture particles present in the air conditioning system so that freezing of moisture does not occur at low temperatures.
• The pressure in the receiver between 5 kg/cm² to 20 kg/cm²
• This pressure depends on the speed of the compressor and temperature of the environment.

Expansion valve

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Cooling

• If the refrigerant expands suddenly at very low pressure so the reason for this is the cooling effect.
• Cooling – Cooling effect is created through the evaporator coil. Refrigerating system operates with the effect of cooling it placed in the chamber of the automobile.
• The evaporator coil cools the air circulated in the passenger compartment. 

gas mileage

• By turning on conventional petrol the fuel economy of the engine reduces by about 20%. when if air conditioner is used in hybrid gas electric vehicle then there is more loss in gas mileage due to this.