A/C test
as the percentage of antifreeze in the coolant increases,.........
the freezing point decreases ( tup to a point)
how is the A/C compressor lubricated in an R-134a system?
the oil moves through the system simply with the movement of the refrigerant
what coolant is used in a motor/electronics cooling system?
the same coolant that is used in the ICE cooling system.
which statement is true about thermostats?
the temperature marked on the thermostat is the temperature at which the thermostat should start to open.
a coolant heat storage tank can keep coolant warm for a maximum of .......... days
three
why is it important to keep refrigerant oil containers closed?
to keep it from absorbing moisture from the air.
what is the purpose of a compressor speed sensor?
to let the ECM know if the compressor is turning.
water discovered on the floor on the passenger side of a vehicle is an indication of what problem?
Clogged evaporator drain
wobble plate compressors commonly use how many cylinders?
Five or seven
O-rings used in R-134a systems are usually.....
Green
asian red coolant is what type?
HOAT
electrically powered A/C compressors should use what type of refrigerant oil?
POE
which refrigerant has the lowest Global warming potential (GWP)?
R-744
which unit contains a desiccant to remove moisture from the system?
Receiver drier and Accumulator
most piston compressors use what type of valves?
Reed
A .......... is a variable valve that changes the size of the valve opening in response to the cooling load of the evaporator.
Thermal expansion valve (TXV)
rear air conditioning systems use......
an orifice tube to control the refrigerant flow into the front evaporator and a TXV with the rear evaporator.
rear air conditioning systems use........
an orifice tube to control the refrigerant flow into the front evaporator and the rear evaporator.
what should the technician use when checking for diagnostic trouble codes?:
any enhanced scan stool that can read body and/or chassis codes
several different methods of leak detection are available including.......
any of the above
water pumps........
are driven by the engine crankshaft or camshaft
Heat intensity is measured in ............ a. BTUs b. degrees c. RH d. calories
b. Degrees
A psychrometer measures ......... a. temperature b. relative humidity c. amount of heat d. radiation
b. Relative humidity
what type of pump is a typical water pump?
centrifugal
pressures are controlled in an orifice tube (OT) system by .......... a. using a variable valve b. cycling an electromagnetic compressor clutch on and off as needed c. using a variable displacement compressor d. either b or c
d. either b or c
what type of refrigerant oil is used in R-134a system? a. POE b. PAG c. mineral d. either a or be depending on the vehicle
d. Either a or b depending on the vehicle
what can be done to prevent air from getting trapped in the cooling system when the coolant is replaced? a. pour the coolant into the radiator slowly b. use a coolant exchange machine that draws a vacuum on the system c. open the air bleeder valves while adding coolant d. either b or c
d. Either b or c
precautions when working with refrigerants include........... a. wear safety goggles or a clear face shield and protective clothing(gloves) when working with refrigerants b. always be in a well ventilated shop area when working with refrigerants and avoid small, enclosed areas c. when refrigerant containers are filled. reserve room is left for expansion and the container is marked with is critical temperature. d. all of the above
d. all of the above
the condenser.............. a. is a heat exchanger b. is a device where air passing over it cools the refrigerant and causes it to change into a high temperature liquid c. transfers heat from the refrigerant to the air flowing d. all of the above
d. all of the above
the water pump drive should be checked for....... a. proper tension b. condition c. wear using a gauge d. all of the above
d. all of the above.
the air inlet control door is also called........ a. fresh air door b. recirculation door c. outside air door d. any of the above
d. any of the above
switches located on the compressor itself may include.......... a. a low pressure switch b. high pressure switch c. low and /or high pressure sensor d. any or all of the above
d. any or all of the above
A compressor speed (belt lock) sensor is used by the HVAC ECM to........ a. prevent a locked up compressor from destroying the engine drive belt b. determine if the compressor is running, and by comparing the compressor and engine speed signals c.vary the displacement of the compressor based on compressor speed d. both a and b
d. both a and b
DEX COOL is.............. a. propylene glycol b. ethylene glycol c. is silicate and phosphate free d. both b and c
d. both b and c
air conditioning process works through a fluid, called a ......... that continuously changes state from liquid to gas and back to liquid. a. element b. conductor c. insulator d. refrigerant
d. refrigerant
PHOAT coolant is what color?
dark green
"outside air" is also called.........air.
fresh
when the HVAC controls are placed on the "heat" position, where does the air flow?
from the floor and windshield (defrost) vents
the high side of the refrigeration cycle means it..........
has higher pressures and temperatures.
a typical vehicle heater works by.......
heat transfers form the coolant, to the fins, and to the air passing through the core.
a seat filter is used with what type of system?
heated and cooled seats
heat travels from.......
hot to cooler
where is the ozone layer ?
in the stratosphere
which sensor might use an aspirator tube?
in vehicle temperature
the low side of the refrigeration cycle meas.......
it has low pressure and temperature
if the cooling system is low on coolant, what is a common symptom?
lack o heat from the heater, but only when the vehicle is at idle, yet plenty of heat when the engine is operating at highway speeds.
an electrical conductor is an element with.......... electrons is its outer orbit.
less than 4
R-134a is in what color container?
light blue
as the latent heat of condensation is transferred to the airstream in the condenser, the refrigerant changes into .........
liquid
what could be wrong if the A/C compressor clutch cycles on and off rapidly?
low refrigerant charge
the lower the GWP number, the .........
lower the global warming potential
like charges .............
repel each other
the advantages of a TXV system over an orifice tube system include........
requires a smaller refrigerant charge
the low-side pressure is low and the high-side pressure is higher than normal. what is the most likely cause?
restriction in high-side line
if an insulated wire gets rubbed through a part of the insulation and the wire conductor touches the steel body of a vehicle, the type of failure would be called a(n)........
short-to-ground
if two power-side insulated wires were to melt together at the point where that copper conductors touched each other, the type of failure would be called a(n).......
short-to-voltage
the advantages of an orifice tube system over a TXV system include.........
simpler and cheaper to produce
if a wire repair, such as that made under the hood or under the vehicle, is exposed to the elements, which type of repair should be used?
solder and adhesive-lined heat shrink or crimp-and-seal connectors.
A "fin comb" is used to........
straighten and align cooling fins on a condenser or radiator
two technicians are discussing A/C systems. technician a says that the TXV system uses a receiver drier mounted in the suction line. technician B says that the orifice tube system uses an accumulator in the suction line . which technician is correct?
technician B only
what is called "black death"?
teflon from the compressor piston rings.
the door used to control interior temperature is called the .........door
temperature blend
heat transfer is improved from the coolant to the air when the.........
temperature difference is great
the ram air that enters the vehicle from the outside enters the HVAC system from.......
the base of the windshield
what does the snowflake button on the dash do?
turns on the A/C compressor
what helps prevent water pump cavitation?
using the specified pressure cap
heat is transferred from the hot coolant flowing through the ........... to warm the air lowing through the fins of the heater core.
water tubes
how does a thermoelectric device (TED) work?
when electrical current flows through the module, one side is heated and the other side is cooled.
what is the most common type of sun load sensor?
photodiode
what diagnostic trouble cod (DTC) could be set if the thermostat is defective?
P0128
some cabin filters contain............. to absorb odors.
Activated charcoal
the letter "a" in R-137a means,.............?
Asymmetrical
the heating element is designed to warm the seat and/or back of the seat to about..........
100F (38C)
in a dual compressor that uses both an ICE powered part and an electrical-power part, what percentage of the capacity is electrically powered?
15%
the normal operating temperature (coolant temperature) of an engine equipped with a 195F thermostat is .......
195F to 215F
the temperature difference between the inlet and outlet of the condenser should be.......
20F-50F
AC vent temperature at the center outlet should be.........
35F-45F (2C-7C)
the proper dash vent temperature for an air conditioning system should be:
35F-45F (2C-7C) or 30F (15C) cooler the the outside air temperature
when testing a relay using an ohmmeter, which terminals should be touched to measure the coil resistance?
86 and 85
most systems use a flap door that swings about..........degrees.
45 to 90
humans prefer relative humidity that is between ......... and .........
45% : 55%
most experts recommend that the system be drawn down to how many microns?
500 or lower
A high -speed CAN BUS communicates with a scan tool through which terminal(s)?
6 and 14
what section of the Clean Air Act concerns work on air conditioning systems in vehicles?
609
Humans prefer temperatures that are between .............and .........
68F: 78F
a container of R-134a tested at a pressure of 115 PSI at an ambient temperature of 75F. this means..........
Air is in the refrigerant
an actuator can be capable of how many position(s)?
All of the above
automatic temperature control (ATC) diagnosis includes .......
All of the above
high resistance in an electrical circuit can cause ........
All of the above
most A/C performance tests include........
All of the above
section 609 of the Act gives EPA the power to enforce .......
All of the above
when retrofitting a system from R-12 to R-134a, what is required to be done?
All of the above
why should service technicians check a system for the presence of sealant before recovering the refrigerant?
All of the above
what is used to help keep the passenger compartment warm during idle-stop(start-stop) operation?
An auxiliary electric water pump
A refrigerant leak can be detected by.........
Any of the above
AC compressor drive belt tension can be measured by......
Any of the above
an airflow (blend) door may be broken if........
Any of the above
the control module used for automatic climatic control systems is called.......
Any of the above depending on the make and model of vehicle
the AC compressor clutch is being checked to see if it is engaged. technician A says that if the drive belt is moving, the compressor is working. technician B says that the compressor will often "click" when it is energized and de-energized. which technician is correct?
Both technician A and B
technician A says that some cabin filters are accessible behind the glove compartment. technician B says that some cabin filters are accessible from under the hood. which technician is correct?
Both technicians A and B
the coolant heat storage system is being discussed. technician A says that the water valve is driven by an electric motor. technician B says that the storage tank has its own electric water pump. which technician is correct?
Both technicians A and B
two technicians are discussing variable displacement piston compressors. technician A says that the wobble plate is moved to the high angle position for maximum output when the cooling load i high. technician B says that the wobble plate angle is controlled by the pressure in the crankcase of the compressor. which technician is correct?
Both technicians A and B
A voltmeter was used to check the coolant and a reading of 0.2 volt with the engine off was measured. a reading of 0.8 volt was measured with the engine running and all electrical accessories turned on. technician says that the coolant should be flushed to solve the galvanic activity. technician b says that the ground wires and connections should be inspected and repaired to solve the electrolysis problem. which technician is correct?
Both technicians a and b
two technicians are discussing testing coolant for proper pH. technician A says that coolant has a pH above 7 when new and becomes lower with use in an engine. technician B says that OAT and HOAT coolants have a lower pH when new compared to the old green IAT coolant. which technician is correct?
Both technicians a and b
the storage container for recovered refrigerant must be approved by.......
DOT
the upper radiator hose collapses when the engine cools. what is the most likely cause?
Defective pressure cap
cabin filters can be replaced and are located by an access panel........
Either a or b
which condition can cause the air conditioning system to produce less than normal cooling.
Either under or overcharged
a clutchless damper drive is used with what type of A/C compressor?
Electronic controlled, variable displacement compressor
what is the SAE specification number of an RRR machine that meets the 2006 and newer standards?
J-2788
the heater control valve, if used, shutsoff the coolant flow to the heater core when what setting is selected?
MAX cooling
A module is also known as a ........
Node
what component cannot be flushed?
None of the above can be flushed?
DEX COOL is what type of coolant?
OAT
what is the color of the plastic conduit used over high voltage wiring to an electric A/C compressor?
Orange
technician A says that PTC heaters can be built into a conventional heater core assembly. technician B says that a PTC heater's electrical resistance will decrease as its temperature increase. which technician is correct?
Technician A only
most recent HVAC actuators are recalibrated after replacement by.......
Using a scan tool or allow it to self learn after being installed
a "pop" is heard from the radio speaker(S) when the system is operating with the air conditioning on. what is the most likely cause?
a defective compressor clutch diode
a five wire actuator uses two wires to power the motor (power and ground) and three wires for .........
a feedback potentiometer
a stretch type A/C compressor belt is removed using.......
a knife (cut it)
what is a "reheat" system?
a system that cools the air through the evaporator then heats the air though airflow though the heater core.
an air conditioning system cools the interior of the vehicle by....... a. moving the heat from inside the vehicle to outside the vehicle b. blowing cold air into the interior c. moving heat from inside of the vehicle to the engine cooling system d. using the engine to move air
a. moving the heat from inside the vehicle to outside the vehicle
when should the service technician check fort technical service bulletins?
after checking for any stored diagnostic trouble codes.
in a piston type compressor, the pistons are driven by a ........ a. crankshaft b. swash plate c. wobble plate d. all of the above depending on the compressor
all of the above depending on the compressor
the liquid line .......... a. connects the condenser to the receiver drier and TXV or OT b. is smaller than the suction line c. is larger in diameter than the suction line d. both a and b
both a and b
technician A says that a good relay should measure between 60 ohms and 100 ohms across the coil terminals. technician B says that OL should be displayed on an ohmmeter when touching terminals 30 and 87, which technician is correct?
both technicians A and B
twenty degrees Celsius is about how many degrees Fahrenheit? a. 25 b. 45 c. 65 d. 85
c. 65
A BTU is measure of .......... a. temperature b. relative humidity c. amount of heat d. radiation
c. amount of heat
heat transferred through the air is called.......... a. radiation b. insulation c. convection d. conduction
c. convection
the three different phases or states of matter include..... a. solid, water, and steam b. ice, liquid, and gas c. solid, liquid and gas d. liquid, water, and steam
c. solid, liquid and gas
the refrigerant is circulated through the system by a .........
compressor
what is commonly wrong when the heat from a heater " comes and goes"?
cooling system is low on coolant
a cooling module usually includes what components? a. radiator b. automatic transmission fluid cooler c. A/C condenser d. all of the above
d. All of the above
various electrical switches used in A/C systems....... a. prevent evaporator icing b. protect the compressor c. control fan motors d. all of the above
d. All of the above
what i true about a SNAP refrigerant? a. requires unique set of fittings, and all ports not converted must be permanently disabled. b. each refrigerant must have a label with a unique color that specifies pertinent information. c. all original refrigerants must be removed before charging with the new refrigerant d. all of the above
d. All of the above
what is the purpose of a flow restrictor,if used? a. slow the coolant velocity as it passes through the heater core. b. to reduce noise c. allow for a better heat transfer to the fins/air d. all of the above
d. All of the above
adding a chemical to make ethylene glycol coolant bitter to the taste is called........
embittered
coolant is water and ...........
ethylene glycol
in most hybrid electric vehicles, the air entering the plenum chamber passes through the.........
evaporator
the orifice tube is usually located at the inlet tube to the..........
evaporator
when the refrigerant evaporate, it absorbs heat when it changes from liquid to gas. in which unit does this occur?
evaporator
reusing old coolant is generally not approved by vehicle manufacturers except.......
mercedes
A musty, moldy smell in the air-conditioning system is usually due to.........
mildew-type fungus growth
the ..........door is used to select air discharge location such as floor, vent, or defrost.
mode
All of the following statements about hybrid electric vehicle A/C compressors are true, except........
most are reciprocating piston designs
coolant is hottest in which area?"
near the thermostat
clear water is seen dripping from beneath the vehicle on the passenger side. this means.........
normal operation
which sensor is also called the ambient air temperature sensor?
outside air temperature (OAT)
the basic designs of A/C compressors include ..........., ..........., and.......?
piston, vane and scroll
A feedback potentiometer is used to...........
provide feedback to the controller as to the location of a door or valve.
present standards and good work habits require that recovered refrigerant be ........
recycled
