ac homework

The sensitivity of the electronic leak detector is ____________________ per year.

0.15 oz per year (4 grams/year)

The maximum moisture content allowable in new refrigerant is __________________ .

10 ppm

"In Denver, Colorado, water (H2O) boils at a temperature of ____________________ degrees fahrenheit."

206.2

A vehicle is brought into the shop with a complaint of weak air flow from all the dash vents. Which of the following is the most likely cause?

A dirty cabin air filter

"In a normally operating system, the refrigerant is in different physical states (vapor or liquid) at the various sections of the system. All of the following are physical states the refrigerant would be found in at various specific locations except:"

A low-pressure vapor and liquid at the evaporator.

"The rear evaporator duct is cooling properly on a vehicle with a rear heating and cooling system, but the front evaporator duct temperature is too warm. What is the most likely cause of this condition?"

A misadjusted front blend door

"What is the state of the refrigerant as it immediately enters the evaporator, line 1? Technician A says it is all liquid with some flash gas. Technician B says it is all vapor. Who is correct?"

A only

Refrigeration system evacuation is being discussed.Technician A says the refrigeration system should be evacuated for a minimum of 30 minutes. Technician B says evacuation is not necessary if the refrigeration system is opened only for a brief period of time. Who is correct?

A only

Technician A says an air-conditioning system that uses a thermostatic expansion valve has a receiver-drier in the liquid line. Technician B says an air-conditioning system that uses a receiver-drier has an accumulator in the liquid line.Who is correct?

A only

Technician A says that the component identified by B is an evaporator. Technician B says that the component identified by A is a condenser. Who is correct?

A only

Technician A says that the ideal superheat for an automotive air-conditioning system is 10 20 °F. Technician B says that flash gas is a contributing factor of superheat. Who is correct?

A only

Technician A says that up to 20 percent of fresh air provides a means to maintain a positive in-vehicle pressure when the windows are closed. Technician B says this positive pressure is necessary to provide a proper balance of air pressure within the air delivery system. Who is correct?

A only

Technician A says the compressor changes a low-pressure vapor to a high-pressure vapor. Technician B says that the metering device changes high-pressure vapor to a low-pressure vapor. Who is correct?

A only

Technician A says the condenser is a heat exchanger for the superheated refrigerant in the system. Technician B says the accumulator is a heat exchanger that removes heat from the air flowing across the evaporator cooling fins. Who is correct?

A only

Two technicians are discussing airflow in an air conditioning system.Technician A says a small amount of conditioned air may be directed to the defroster outlets to prevent windshield fogging.Technician B says up to 10% fresh (outside) air is mixed with re-circulated air, while in recirculate mode, to prevent exhaust gasses from entering the passenger compartment.Who is correct?

A only

Vacuum pump efficiency is being discussed: Technician A says that vacuum pump efficiency is greatest at sea level. Technician B says that altitude has little or no effect on vacuum pump efficiency. Who is correct?

A only

What is the state of the refrigerant in line 4? Technician A says that it is high-pressure vapor. Technician B says that it is high-pressure liquid. Who is correct?

A only

All of the following are important properties that an automotive refrigerant must exhibit except:

A refrigerant must be explosive or flammable.

All orifice tube systems have a(n) ___________________ at the outlet of the evaporator.

Accumulator

Mode doors may be operated

All of the above By vacuum By cable By electricity

The airflow path in the case/duct system illustrated in Figure 9-52 is being discussed: Technician A says that airflow is also through the heater core in the cooling mode. Technician B says that airflow is also through the evaporator in the heating mode.

B only

What component is shown as C? Technician A says that it is an accumulator. Technician B says that it is a receiver-drier. Who is correct?

B only

What is the purpose of the desiccant? Technician A says it is to clean the refrigerant. Technician B says it is to dry the refrigerant. Who is correct?

B only

"Fluorescent leak detector scanner solution is being discussed: Technician A says once introduced into the system, it can only be removed by flushing it out of they system. Technician B says a fluorescent light is required for detecting a leak. Who is correct?"

Both A and B

"Technician A says that air conditioning is the process where air is cleaned, filtered, and recirculated. Technician B says that air conditioning is the process of cooling air by removing some of its heat. Who is correct?"

Both A and B

An R-134a expansion valve system that is properly charged has the following gauge readings, high-side 320 psig and low-side 50 psig and the ambient air temperature is 80°F. Which of the following is the most likely cause? Technician A says an air flow restriction through the condenser could be the cause. Technician B says the refrigerant system could be overcharged. Who is correct?

Both A and B

Technician A says heat-laden refrigerant gives up its' heat in the condenser as it changes from a vapor (gas) to a liquid.Technician B says cold, low pressure liquid absorbs heat in the evaporator and changes from liquid to vapor as the refrigerant absorbs heat. Who is correct?

Both A and B

Technician A says refrigerant that is contaminated with another type of refrigerant can cause damage to the refrigeration system and present diagnostic problems if you are not aware of its' presence.Technician B says refrigerant that is contaminated with hydrocarbons (propane or butane) can cause damage to the refrigeration system and present diagnostic problems if you are not aware of its' presence. Who is correct?

Both A and B

Technician A says that a sight glass is often found in an R-12 system. Technician B says that a sight glass is seldom found in an R-134a system. Who is correct?

Both A and B

Technician A says that service ports may be a source of leaks. Technician B says that hoses are sometimes a source of leaks. Who is correct?

Both A and B

Technician A says that the component identified by A is a receiver-drier. Technician B says that the component identified by D is a condenser. Who is correct?

Both A and B

Technician A says that the line or hose that connects the compressor outlet to the condenser inlet is called the discharge line. Technician B says that the line or hose that connects the evaporator outlet to the compressor inlet of a TXV system is called a suction line. Who is correct?

Both A and B

Technician A says that the recommended oil for most R-134a systems is PAG oil. Technician B says that the recommended oil for R-12 systems is a mineral-based oil. Who is correct?

Both A and B

Technician A says the Delta T method of adjusting the charge levels of the refrigerant system relies on a comparison of the inlet and outlet temperatures of the evaporator. Technician B says systems should always be checked first for refrigerant contamination. Who is correct?

Both A and B

Technician A says the compressor is one of the points in the air-conditioning system where there is a separation between a high and a low pressure. Technician B says the metering device is one of the points in the air-conditioning system where there is a separation between a high and a low pressure. Who is correct?

Both A and B

Technician A says the compressor is one of the points in the air-conditioning system where there is a separation between low and high pressure. Technician B says the metering device is one of the points in the air-conditioning system where there is a separation between high and low pressure.Who is correct?

Both A and B

Technician A says the compressor separates the low side of the system from the high side of the system. Technician B says the metering device separates the high side from the low side of the system. Who is correct?

Both A and B

Technician A says the condenser is a heat exchanger for the superheated refrigerant in the system. Technician B says the evaporator is also a heat exchanger for the refrigerant in the system. Who is correct?

Both A and B

Technician A says the system shown is a fixed orifice tube-type refrigeration system. Technician B says the FOT is the dividing point between the high- or low-side system pressures. Who is correct?

Both A and B

Technician A says the system shown is an expansion valve refrigeration system. Technician B says the expansion valve is the dividing point between the high- or low-side system pressures. Who is correct?

Both A and B

Technician A says there is a direct relationship between temperature and pressure in an automotive air-conditioning system. Technician B says that increased humidity increases the heat load on the refrigerant system. Who is correct?

Both A and B

Technician A says there is a direct relationship between the pressure and temperature of a refrigerant. Technician B says any apparent temperature-pressure relationships in a contaminated system are not valid. Who is correct?

Both A and B

Technician A says when the pressure of R-134a is high, the temperature will be high. Technician B says when the temperature is low, the pressure will be low. Who is correct?

Both A and B

The MIX selection mode is being discussed.Technician A says it is basically the same as the Hi/Lo mode on other vehicle models.Technician B says the MIX selection mode is basically the same as the bi-level mode on other vehicle models.Who is correct?

Both A and B

The air conditioning case and duct system is being discussed.Technician A says the case system provides a housing for the components.Technician B says the duct system provides a passage for the airflow.Who is correct?

Both A and B

The desiccant, a drying agent, is being discussed.Technician A says the desiccant is found in the accumulator. Technician B says the desiccant is found in the receiver-drier. Who is correct?

Both A and B

The function of the air conditioning compressor is being discussed.Technician A says the function of the compressor is to circulate refrigerant.Technician B says the function of the compressor is to raise pressure.Who is correct?

Both A and B

The use of ultraviolet dye is being discussed. Technician A says a cold type of leak warrants the use of ultraviolet dye in order to find the source of the leak. Technician B says a slow leak warrants the use of ultraviolet dye in order to find the source of the leak. Who is correct?

Both A and B

What is the state of the refrigerant in line 5? Technician A says that it is low pressure. Technician B says that it is a vapor. Who is correct?

Both A and B

In the MIX/BILEVEL position, conditioned air is delivered to the ____ outlet.

Both A and C Defrost Floor

Cooled air is generally delivered into the passenger compartment through the ___________________ vents.

Dash or Panel

"During normal air-conditioning system operation, the position of the system mode doors:"

Depends on the mode selected.

There are two types of blower systems: an upstream blower and a ___________________ blower system.

Downstream

All of the following are forms of heat transfer that take place as it relates to the vehicle air-conditioning system except:

Evaporation

A refrigerant system with air contamination will still operate properly.

False

Ice on the evaporator coil is often a normal condition.

False

The evaporator is said to be flooded if too little refrigerant is metered into it and starved if too much refrigerant is metered into it.

False

Heated air is generally delivered into the passenger compartment through the ___________ __________________.

Floor vents

The compressor may operate in the heat mode to help maintain in-vehicle ___________________.

Humidity

A ____________________ acid is formed by the chemical combination of refrigerant and moisture.

Hydrochloric

"To address the issue of small capacity refrigerant systems, the EPA adopted a new SAE standard effective December 2007, covering the accuracy level of future refrigerant recovery, recycling, and recharging equipment. The SAE number for this new standard is:"

J2788

An inoperative vacuum motor could be caused by all of the following, except:

Mode door cable misadjustment

When the air-conditioning system is first turned on, a musty odor comes from the vents. What is the most likely cause for this ?

Mold formation on the evaporator core

"Technician A says that an overcharged system will result in lower than normal low-side pressures. Technician B says that an overcharged system will result in a slight increase in cooling capacity, but only under low load conditions. Who is correct?"

Neither A nor B

Technician A says the fixed orifice tube can vary the amount of refrigerant allowed to flow to the evaporator. Technician B says the thermostatic expansion valve has a fixed opening and cannot vary the amount of refrigerant allowed to flow to the evaporator. Who is correct?

Neither A nor B

Technician A says refrigerant changes from a liquid to a vapor in the condenser.Technician B says refrigerant changes from a vapor to a liquid in the evaporator. Who is correct?

Neither A or B

Technician A says that if a thermostatic expansion valve malfunctions, it may be repaired rather than replaced. Technician B says that an expansion tube, better known asa fixed orifice tube (FOT), has a remote bulb that controls the opening and closing of the orifice to vary the amount of refrigerant entering the condenser. Who is correct?

Neither A or B

Most original equipment manufacturers use what type of lubricant in their R-134a systems?

PAG

An air-conditioning system ____________________ is an initial test that determines whether the refrigerant system is operating as designed.

Performance test

In the case and duct system the air distribution mode doors may be operated by all of the following except:

Potentiometers

"R-134a, when used as a refrigerant, exhibits a predictable relationship between pressure and temperature, and a stable change of state point between a liquid and a gas under various pressures and temperatures. All of the following are true of the temperature pressure relationship of R-134a except:"

Refrigerant in the liquid state can make a change of state to a gas (vapor) by increasing the pressure on the refrigerant without changing its temperature.

Refrigerant system air contamination may be caused by:

Refrigerant system low-side leak. Improper system evacuation or insufficient evacuation time. Weak evacuation pump. All of the above.

Heat transfer and refrigerant state are being discussed. Technician A says as cold refrigerant flows through the evaporator core, the heat from the warmer air passing over the evaporator fins will transfer its' heat into the cooler refrigerant lowering the air's temperature and causing the refrigerant to boil in the evaporator. Technician B says as low temperature, high pressure refrigerant flows through the evaporator core, the heat from the warmer air passing over the fins will transfer its' heat into the cooler refrigerant lowering the air's temperature and causing the refrigerant to condense in the evaporator. Who is correct?

Technician A only

"Technician A says the air-conditioning system low- and high-pressure lines and hoses are different in diameter. To identify the lines, the high-side line is larger in diameter than the low-side line. Technician B says the low side line is larger in diameter than the high side line. Who is correct?

Technician B only

On a refrigerant system, there is heavy frost on the expansion valve inlet and low-side pressure is well below normal. Technician A says that the expansion valve is stuck in the open position and this could be the cause. Technician B says that a restricted expansion valve inlet screen could be the cause. Who is correct?

Technician B only

Moisture removal from a refrigerant system is being discussed. The length of system evacuation time required depends on all of the major factors listed below except:

The amount of oil in the system.

One of the functions of the air conditioning compressor is to increase the pressure of the refrigerant. Another function of the compressor is to increase:

The heat (temperature) of the refrigerant

"The following statements about a typical system set to MAX cooling are true, except:"

The outside/recirculate door is in the outside, or fresh air, position.

An R134a recovery tank pressure is determined to be 115 psig at 85 °F. What does this temperature-pressure relationship indicate?

The recovery tank is contaminated with air.

Which of the following statements identifies the correct state and pressure of the refrigerant throughout the system?

The refrigerant is low pressure at points 1 and 5 in the system and high pressure at points 2, 3, 4, and 6 in the system.

The most accurate method for measuring the effectiveness of system evacuation is with the use of a:

Thermistor vacuum gauge.

Air in the refrigerant system is considered a non-condensable gas because at no time are refrigerant system pressures great enough or temperatures low enough to cause air to condense into a liquid.

True

Moisture in a refrigerant system may cause intermittent poor system performance.

True

On a cycling-clutch system, the desired average temperature of the evaporator should be about 35 °F (1.7 °C).

True

Poor passenger compartment cooling may be the result of dirt or debris plugging the evaporator core cooling fins.

True

Refrigerant lubricant (oil) is stored in the compressor and is essential to keeping the internal parts of the compressor lubricated.

True

Restricted airflow through the condenser core will result in higher than normal high-side pressures.

True

Some systems that are equipped with a cabin air filter are also equipped with an airborne pollutant (air-quality) sensor.

True

The dual-zone duct system found in some cars has a separate driver and passenger side duct system.

True

The outlet of the metering device is usually the coolest part of the system under normal operating conditions.

True

The symbol for mercury (hg.) is used to denote a vacuum pressure.

True

During a refrigerant system performance test, it is noticed that both high-side and low-side pressure readings are about the same. Which of the following could be the possible cause?

a faulty compressor

On a properly charged R-134a cycling clutch type A/C system, the evaporator is icing. Which of the following could be the cause?

a faulty pressure cycling switch

A technician is checking refrigerant system pressures. Both high- and low-side service ports are located on the A/C compressor. When the compressor is engaged, the high-side pressure instantly goes over 375 psig. What is the most likely cause of this condition?

a restricted discharge hose

An R-134a expansion valve system that is properly charged has the following gauge readings, high-side 150 psig and low-side 42 psig and the ambient air temperature is 85°F. Which of the following is the most likely cause?

a stuck open expansion valve

An air-conditioning system that uses a fixed orifice tube has a(n) ___________________ in the suction line.

accumulator

On a properly charged R-134a system, an A/C performance test indicates both normal high- and low-side pressures, but poor cooling. Which of the following is the most likely cause?

an improperly adjusted temperature blend door

Humidity in the passenger compartment can be increased by all of the following, EXCEPT:

compressor operation

If the low-side gauge pressure is showing a vacuum, all of the following defects could be the cause, EXCEPT __________.

compressor valves worn

A manifold and gauge set is attached to an operating air conditioner. The low-side gauge reading is too high and the high-side reading is too low. What could be the problem?

defective compressor

Which of the following could cause very low pressures on the low side of a system equipped with an expansion valve?

expansion valve stuck closed

High-pressure liquid refrigerant moves through a hose called a ___________________.

liquid line

An undercharged system will show which of the following gauge readings?

low side, low; high side, low

O-ring damage could be caused by __________.

overtightening burrs on the fitting using the wrong type of O-ring all of the above

The temperature at which refrigerant vaporizes or condenses is the _____ temperature.

saturation