HVAC Control Systems 403b

Question 1

What type of controls are used by the driver to turn the system ON, and adjust air temperature, airflow direction and velocity?

Answer 1

active

Question 2

What type of controls regulate the flow of air conditioning refrigerant or heater coolant without driver input?

Answer 2

passive

Question 3

What type of controls may prevent or support system functions?

Answer 3

supplemental

Question 4

The blower speed switch has three ON positions to control blower fan speed and regulate the HVAC system air velocity, which is measured in:

Answer 4

CFM (cubic feet per minute)

Question 5

The engine coolant water valve is a passive control that allows the operator to set the amount of hot engine coolant that will pass through the heater core.
T/F

Answer 5

false; The engine coolant water valve is an active control.

Question 6

A seized open engine coolant water valve will cause the truck cab to remain very warm even when the truck’s air conditioning is operating, when warm spring and summer weather occurs.
T/F

Answer 6

true; This is a major problem every spring in northern climates.

Question 7

A 12-volt electromagnetic clutch coil is indicated by a:

Answer 7

black lead wire

Question 8

The first passive control in the electrical circuit that energizes the compressor electromagnetic clutch is a:

Answer 8

thermostatic switch

Question 9

When the air conditioning system contains a fixed expansion tube and an accumulator, the thermostatic switch may be replaced with a:

Answer 9

clutch cycling switch

Question 10

Refrigerant low pressure sensing switches are used on thermostatic expansion valve equipped air conditioning systems as a low ambient temperature protection switches.
T/F

Answer 10

true; The ambient temperature switch will protect the air conditioning
compressor from operating with very low refrigerant pressures and a lack of oil circulation.

Question 11

The pressure settings of the high pressure switch must be adjusted ____ ____ the settings of the refrigerant’s pressure relief valve or fusible plug.

Answer 11

lower than

Question 12

The Binary™ switch acts like a _______ _________ switch.

3

Answer 12

• low-pressure
• high-pressure
• ambient temperature

Question 13

How many functions does the Trinary™ pressure switch perform to monitor and control refrigerant pressure inside the air conditioning system?

Answer 13

three

Question 14

List the two (2) devices used to control refrigerant flow into the evaporator core.

Answer 14

• thermal expansion valve

- fixed orifice tube

Question 15

What electrical device is used in HVAC systems to control fan or blower motor speed?

Answer 15

resistor

Question 16

List the two (2) types of blower wheels that are used in HVAC systems.

Answer 16

• single entry blower wheels

- double entry blower wheels

Question 17

A heater system uses ______ _______ to carry excess engine heat energy to warm the cab air.

Answer 17

engine coolant

Question 18

List the three (3) inputs of an air conditioning management system.

Answer 18

• high pressure switch
• low pressure switch
• evaporator thermostatic switch

Question 19

List the three (3) outputs of an automatic temperature control system.

Answer 19

• the heater water control valve
• the fan blower motor
• the air conditioning system compressor

Question 20

When the maximum cooling setting is chosen on the control panel, the air
conditioning switch is turned to the _________________ position. The fresh air
door is set on the __________________ position. The temperature setting is turned
towards the __________________________ setting.

Answer 20

on, recirculation, blue

Question 21

When the maximum heating setting is chosen on the control panel, the air
conditioning switch is turned to the _________________ position. The
temperature setting is turned towards the _______________ setting.

Answer 21

off, red

Question 22

When the maximum defrost setting is chosen on the control panel, the airflow
direction is set towards the _______________ position. The air conditioning
switch is turned to the OFF position. To remove the mist from the windshield,
the air conditioning compressor’s electromagnetic clutch is ________________
and the evaporator will cool and _________________ the recirculated cab air.

Answer 22

defrost, engaged, dehumidify

Question 23

A manual climate control HVAC system is called a _____________________
_______________________ system.

Answer 23

temperature blend air door

Question 24

The truck’s _______________ must be operating if the sleeper compartment is to be
heated or cooled.

Answer 24

engine

Question 25

When the cooling function on the control panel is chosen, the electrically controlled
refrigerant __________ _________ is opened and refrigerant is
allowed to pass through the sleeper compartment’s ____________
________ _________ and into the evaporator core.

Answer 25

solenoid valve;

thermal expansion valve