Deck 10: System Controlsdiagnosis and Service of System Controls

Question 1

A blower motor is being tested for resistance.Technician A says a higher than specified resistance would cause slower blower operation.Technician B says trash or other items could restrict the blower,causing motor resistance to go up during operation.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Answer 1

C

Question 2

Technician A says to measure current on the blower motor circuit by connecting the DVOM in series at any point between the switch and the motor ground.Technician B says the motor should not be powered while measuring current.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Answer 2

A

Question 3

Self-diagnostic systems display trouble areas as a code.

Answer 3

True

Question 4

The sunload sensor monitors the temperature of the sunlight entering the vehicle.

Question 5

Any pressure below atmospheric pressure is considered a vacuum.

Question 6

The ambient air temperature sensor monitors the temperature of the outside air.

Question 7

Technician A says a fuse can be replaced with one having a higher rating if the original size fuse keeps blowing.Technician B says it is always acceptable to replace a fuse with one having a lower rating.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 8

On an automatic temperature control system the blower motor circuit resistence is specified at 2.0 to 3.5 ohms.If the resistence in the circut falls to 1.5 ohms which of the following will be the most likely result?

A) High current flow in the blower motor circuit.
B) Low current flow in the blower motor circuit.
C) The blower motor will spin faster than designed.
D) The blower motor will spin slower than designed.

Question 9

The blower motor in Figure 10-93 has blower motor speed M2,M3,and High speed.But does not run in either LOW or M1.Which of the faults listed below could be the cause:

A) Faulty blower motor.
B) Faulty blower motor relay.
C) Faulty Heater A/C control assembly.
D) Faulty resistor block.

Question 10

The stepped resistor blower speed control has four or five speed positions.

Question 11

The temperature fluctuates between hot and cold on a vehicle equipped with an automatic temperature control system.Which of the following is the most likely cause?

A) A open blower motor control relay.
B) A low refrigerant charge level.
C) A faulty coolant temperature sensor.
D) A disconnected in-car temperature sensor aspirator tube.

Question 12

Technician A says before attempting to remove the blower motor resistor,ensure that it is not hot.Technician B says the blower motor may have a power module.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 13

Which of the following is the best description of a pressure switch designated nc?

A) It is held closed during normal pressure conditions.
B) It is held closed during extreme low-pressure conditions.
C) It is held closed during extreme high-pressure conditions.
D) It is held open during extreme high-pressure conditions.

Question 14

Major circuits are protected by a fusible link or maxi-fuse.

Question 15

The connector for the blower speed control switch has melted.Which of the following is the most likely cause?

A) An open in the blower motor switch.
B) High than specified blower motor current draw.
C) A shorted blower motor resistor block.
D) An open blower motor resistor block.

Question 16

If blower motor speed control is provided by resistors,the motor will have three windings.

Question 17

Infrared temperature sensors measure surface temperatures rather than air temperature.

Question 18

Air conditioning is not generally required at temperatures below 50°F (10°C).

Question 19

An average rating of an air conditioning system fuse or circuit breaker is ____ amperes.

A) 10 to 20
B) 15 to 25
C) 20 to 30
D) 30 to 100

Question 20

The power control module sends a pulse width modulated signal to the blower motor to regulate blower speeds.

Question 21

Why can the high- and low-side temperature switches be used to measure system pressures?

Question 22

Name four methods of temperature control used on modern air conditioning systems.

Question 23

When will a compressor discharge pressure switch disengage the compressor clutch?

Question 24

Technician A says the purpose of lthe pressure cutoff switch is evaporator temperature control.Technician B says the purpose of the pressure cutoff switch is system protection.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 25

On a vehicle equipped with and automatic temperature control system the blower motor will not function when the vehicle is first started and heat is selected.Which of the following is the most likely cause?

A) The ambient air temperature is faulty.
B) The in-car temperature sensor is faulty.
C) The system is functiong normally.
D) The blower motor has higher than specified resistence.

Question 26

The usual service problem with vacuum reserve tanks is

A) leaks.
B) clogging.
C) moisture collection.
D) collapse.

Question 27

Technician A says to always recover the refrigerant before removing a pressure switch.Technician B says a different pressure range switch may be installed to compensate for a worn but serviceable compressor.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 28

On an automatic temperature control system that will not hold the temperature set at the control panel,what should the technician do first?

A) Replace the incar temperature sensor.
B) Replace the the temperature mode door actuator.
C) Refer to the appropriate manufacuterer service information.
D) Recover and recharge the A/C system.

Question 29

During heavy acceleration a vihicle has sluggish performance when the air conditioning is on.Which of the following is the most likely cause?

A) A restricted cabin air filter.
B) A faulty engine load sensor cut-off system.
C) A faulty condenser cooling fan.
D) A slipping A/C compressor clutch.

Question 30

The air conditioning compressor will not engage.When a scan tool is connected it indicates that there is no A/C request signal.Technician A says that the refrigerant system may have a faulty thermostatic expansion valve.Technician B says that an engine cooling system thermostat which is opening too soon could be the cause.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 31

The vacuum system is used to ____ the heater coolant valve and mode doors to achieve a desired preselected temperature and humidity level.

A) open
B) close
C) position
D) all of the above

Question 32

Electronic control heads are being discussed.Technician A says all units have a connection to use a scan tool or diagnostic tool.Technician B says the different brands use the same trouble code to indicate the same failure.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 33

Name the components in the simplest type of heater/air conditioner control system.

Question 34

Technician A says the pressure cycling switch directly opens and closes the electrical circuit to the compressor clutch coil.Technician B says the pressure cycling switch sends a signal to the microprocessor to turn the compressor on and off.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 35

What is the purpose of the air conditioner control panel?

Question 36

Technician A says a four-speed blower motor control is a five-position switch.Technician B says all blower motors have several windings in the motor to assist in speed control.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 37

A rattling noise is heard when the engine is running and the air conditioning is off.Technician A says this may be caused by a too narrow gap between the compressor's armature and rotor.Technician B says a quick accurate test is to switch on the air conditioning to see if the noise stops.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 38

An air conditioning system has no blower speeds.When the blower motor lead is connected to a 12-volt power source,it begins to operate.Technician A says this means the blower is defective.Technician B says this means the problem is in the control system.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 39

What is the major disadvantage of the telltale light system?

Question 40

What causes a thermistor to change resistance value?

Question 41

What could happen if the reservoir fails to hold vacuum.

Question 42

Explain how the internal circuits of a circuit breaker respond to an overload and how the breaker resets.

Question 43

Why do many systems use a check valve between the engine manifold supply vacuum hose and the reservoir tank?

Question 44

Why is a diode used in the clutch coil circuit?

Question 45

What is a blower motor power module?

Question 46

How does the thermostat control the in-vehicle temperature?

Question 47

What is the relationship of the aspirator to the in-car temperature sensor?

Question 48

Explain what is meant by this sentence: "The change in resistance value of each sensor is inversely proportional to a temperature change."

Question 49

How does the automatic temperature control regulate temperature?