air-conditioning from new book and manual
SAE standard J2791 covering hfc 134a and J2913 covering for hfo 1234yf electronic leak detectors requires improved performance compared to J1627 detectors. detectors certified under this standard have the capability of identifying leakage rates as low as
0.15 ounce per year at a distance of 3/8 inch.
soap bubbles will only identify leaks that are excess of
1100 grams about 40 ounces per year.
152a has similar operating pressures to
134a systems
CFC 12 recovery only and recovery/recycling equipment hoses have
3/8 inch fittings
R-744 carbon dioxide has lowest global warming potential value of new refrigerants how ever systems using R-744 operate at higher pressures
5 to 10 times higher than HFC-134a and HFC-152a
technicians who repair or services MVACs must be trained and certified by an EPA approved section
609 program
tech A says that technical service bulletins are issued by vehicle manufactures. Tech B says that technical service bulletins are not a good resources when looking for information on unusual or frequently occurring problems. who is right
A
HFO-1234yf classified by ASHRAE as an
A2L midly flammable
tech A says telephone hotlines should be used before consulting other sources of service information. tech B says many telephone hotline services have access to technical service bulletins. who is right
B
it is illegal for any persons to knowingly release or vent refrigerants except
CO2 R-744 during maintenance repair and disposal.
under snap Epa listed three low global warming potential refrigerants acceptable for mobile A/C which are
HFO-1234yF, Carbon dioxide R-744, and HFC-152a none of these destroy the ozone layer
EPA regulations require that certified CFC-12 recovery/recycling equipment must conform to the specifications listed in SAE standard
J1990
in 2007 recovery/recycling equipment standard J2210 was superseded by SAE
J2788. equipment provides more complete refrigerant recovery, and also establishes refrigerant charging requirements providing greater accuracy.
MVAC means
Motor vehicle air conditioning
hfc 134a systems use
PAG lube
Before early 1990s A/c systems used what type of refrigerant
R-12
auto manufactures replaced R-12 with
R-134a in mid 1990s
the direct expansion type for HFC-152a is just like a
R-134a system however to address the issue of HFC-152a being flammable system features are required
tech A says in a series circuit only some of the current flows through parts of the circuit. Tech B says a series parallel circuit is a combination of a series and parallel sections. who is right
Tech B
an ? must be allowed to operate for long periods
air pressure pump
identifiers can also provide an accurate indication concerning the amount of
air that may be in an a/c system or storage tank. some state or local laws may require their use.
under section 609
although co2 may be vented section 609 still require that all MVAC systems be serviced through proper use of EPA certified refrigerant handling equipment. this requirement applies regardless of the refrigerant used in the MVAC system. this means that anyone servicing an MVAC system that uses co2 as the refrigerant would need to properly use EPA certified refrigerant handling equipment.
if voltage and resistance are known the tech can use ohms law to find
amperage
the two most common kinds of hose fitting types are the ? fitting and the ? fitting
barb fitting and beadlock fitting
on a late model car which of the following is the most likely to be operated by a cable
blend door
which of the following devices is used to perform open loop flushing
blowgun
low pressure line
blue
a blower motor does not operate. Tech A says the problem could be a switch. Tech B says the problem could be a bad motor ground. who is right
both
a refrigeration gauge manifold body is made of
brass or aluminum
most hvac components are located at the
bulkhead, firewall, or crowl
which of the following is not a dedicated refrigeration service device
charging scale
the vehicles engine should not be running during leak
check. since air movement can affect the detection ability to locate leaks. all fittings and components should be checked on all of their surfaces. leaks can be present at any point at the top or bottom of the part being checked.
too much oil can cause
compressor to liquid slug possibly hydraulically lock up. reduced overall system performance.
today, many manuals and other kinds of paper literature are being replaced by information that can be accessed using a
computer
a refrigeration identifier can help alert you to a/c system refrigerant
contamination problems. you can also use an identifier to help confirm what type of refrigerant is in the container.
the identifier should conform to the specifications outlined in SAE J1771 J2912 or J2927 this assures that the unit
correctly identifies refrigerants. note only J1771 units are required to identify CFC 12
the equipment must also have a label which states
design certified for compliance with SAE J1991
EPA regulations require that certified HFC-134a recovery/recyling equipment must conform to the specifications listed in the appropriate standard the equipment must have a label which states
design certified for compliance with SAE J2210 or J2788
at one time it was thought automotive air conditioning might have to be discontinued because of
destruction of the ozone layer
? can have a letter and four numbers
diagnostic trouble codes DTCs
wire gauge is the measurement of wire
diameter
the 152a secondary loop type incorporates a
direct expansion refrigerant circuit located in the engine compartment with a chiller that cools a non flammable liquid. the non flammable liquid is circulated to a cooling coil that replaces the evaporator. this provides isolation between the flammable refrigerant and the passenger compartment.
the accumulator or receiver-drier holds extra refrigerant and a
dissicant
to pinpoint leaks in a mobile a/c system macs recommends using the SAE J1628 service procedure. this requires the use of a
electronic leak detector certified to SAE standard J1627, J2791 or J2913 as minimum criteria J1627 electronic leak detectors are capable of identifying leakage rates of 0.5 ounces per year at a distance of 1/4 inch from leak point.
the most accurate way to check for leaks is to use an
electronic leak detector.
a good conductor easily gives up
electrons
the modern hvac control system controls all of the following except
engine temp
properly operating recover/recycling equipment will remove
excess air. however many older R/R machines require manual air purge.
a charging station combines all of the following components except
flushing unit
some R-12 refrigeration systems may have special service fittings. these fittings keep the technician from doing what
from crossing the high and low side connections.
what color are contaminated refrigerant containers
gray with yellow tap
what do the initials hvac stand for
heating, ventilation, air conditioning
hot
high pressure
it is important to make sure that recycled refrigerant does not contain air non condensable gas in excess of allowable amounts. if recycled refrigerant contains too much air
high system operating pressure will occur. this will result in loss of air conditioning performance and possible system damage.
the heater core is warmed by
hot coolant
PAG lubricant is
hydroscopic absorbs moisture containers must be kept tightly closed.
the SAE J1628 procedure does not require a fully charged a/c system.
if the system has only a few ounces of refrigerant and at least 50 psig of pressure at approximately 55 fereinheit that is sufficient to check for a leak. static pressure will be higher with the same amount of refrigerant if the working area temperature is warmer. for example with hfc 134a the pressure will be about 125 psig at 100 ferinheit.
under section 608 of the clean air act
intentional release venting of any refrigerant is illegal unless the refrigerant is specifically exempted from the prohibition. CO2 is exempted under 608 meaning that it can be legally vented.
mechanical temperature gauges make use of a ? spring to register temperature changes
internal bimetal spring
too little or the wrong viscosity oil can cause
internal compressor failure
recycled refrigerant
is that which has been processed on site at a service facility using recycling equipment certified to the appropriate SAE J standard
reclaimed refrigerant
is that which has been sent to an EPA listed reclamation facility where it is processed and returned to a state which meets the appropriate ARI 700 specification. the standards of purity for reclaimed refrigerant are much higher than those for recycled refrigerant.
R-12 is refrigerant that is bad to the environment because
it destroys ozone layer which shields us from the suns harmful ultra violet rays
152a drawback
its ASHRAE flammability rating is A2 means will burn when ignited
motor vehicle a/c systems can release refrigerant into the atmosphere in a number of ways
leaks from system part failures and seepage which occur when a leak is not repaired and the system is recharged or topped off. refrigerant released during various service procedures refrigerant released from service equipment manifold gauges and equipment hoses when using small cans to charge a system refrigerant remaining in the can is likely to ultimately be vented. the refrigerant remaining in larger 30 pound disposable containers that has not been recovered is also sometimes vented when they are scrapped collusion or other types of physical damage.
cold
low pressure
the blue hand wheel on a gauge manifold indicates the
low side valve
if a large quantity of lube was removed during recovery the a/c system probably had a
lubricant overcharge
cfc 12 systems use
mineral based lube
older multimeter used a ?
needle that moved against a calibrated background
HFO-1234yf only can be used in
new vehicles with components designed for it
R-134a is not an
not a ozone destroyer but it is still a green house gas
if the system is completely empty it will be necessary to add some refrigerant to the system in order to use an electronic leak detector. about 15%
of the total system charge is enough to obtain a minimum system pressure of around 50 psi
resistance to the flow of electrons is measured in
ohms
how many blend doors do most vehicles have
one blend door
older refrigerant dyes were
orange in color.
to remove as much of the refrigerant as possible during the recovery process systems equipped with the
orifice tubes and accumulators may require more time than systems equipped with expansion valves/reciver-driers
to remove snap rings the technician needs special snap ring
pliers
HFC 134a and HFO 1234yf recovery only and recovery/recycling equipment hoses have
quick couple fittings
what undesirable thing will happen if too much antifreeze is placed in a cooling system
raise the freezing point
the operation of recovery only equipment is similar to the recovery feature of recovery/recycling equipment. however
recovery only equipment is designed for the sole purpose of removing refrigerant from a system it does not recycle refrigerant for reuse. before it can be reused the refrigerant must be recycled through use of a recovery/ recycling machine which meets the appropriate SAE standard or sent off site to be reprocessed to the appropriate a/c and refrigeration institute ARI 700 specification.
to prevent refrigeration contamination
recovery/recycling equipment must only be used with one designated refrigerant.
recovery/recycling equipment is not designed to
recycle or separate contaminated refrigerants. contaminated or unknown refrigerant must be removed from a system using dedicated recovery only equipment, and properly disposed of. under federal law contaminated refrigerant cannot be vented.
high pressure line
red
heating the accumulator with devices such as a hair dryer or electric heating pad will raise the pressure in the accumulator and
reduce the amount of time necessary for refigerarant removal
carefully inspect
refrigerant connections, joint seals and seal surfaces for signs of wear, deformation, contamination or damage. when reassembling components ensure proper alignment of male/female connections and seal then tighten the connection to the correct torque value specified by the manufacturer.
all of the following statements about refrigerant are true except
refrigerant must not change from a gas to a liquid during normal refrigeration system operation
during the recovery process as the system is drawn into a vacuum and pressure in the accumulator is lowered the accumulator becomes very cold with external frost sometimes visible on the accumulator. this makes it even more difficult to extract remaining refrigerant from it. if all or most of the refrigerant has not been removed and the refrigerant lines are disconnected a sudden
release of refrigerant and oil can occur.
the job of the desiccant is to
remove moisture from the refrigerant
The EPA and macs recommend that leaking should be
repaired
motors turn electricity into
rotation
section 608 of the clean air act requires that all persons who
sell CFC and HCFC refrigerants must retain invoices that list the name of the purchaser the date of the sale and the quantity of refrigerant purchased
in a ? circuit current flows through every part of the circuit
series
since january 1 1992 for CFC 12 and November 15 1995 for HFC 134a and other A/C refrigerants any person
servicing mobile air conditioning pressurized refrigerant circuit must comply with the clean air act and must use either refrigerant recovery/recycling or recovery only equipment approved by the EPA. those working for money who open the refrigeration circuit must be certified by an EPA approved organization to legally use such equipment to service the system.
an electronic leak detector is being used to check for leaks. the detector begins to squeal loudly. which of the following is the most likely cause
severe refrigerant leak
hoses used with mobile a/c system service equipment must be equipped with
shut off valves. the valves may be located within 12 inches of the vehicle end of the service hose and most equipment manufactures incorporate the shut off valve in their quick couplers these automatically shut off the flow of refrigerant when the hoses are disconnected.
hybrid vehicles with electrically driven compressors use
special a/c system lube
hvac fans are called
squriieal cage blower
define refrigeration system static pressure
static pressures are the pressures in the refrigeration system when the system is not operating.
a specialized manual covers a specific vehicle
system
refrigerant contaminated with any air, chemical, additives, or other refrigerants can cause
system operating problems
the blend door controls the ? of air entering the passenger compartment
temperature
any person who owns refrigerant recovery/recycling equipment and provides service for monetary value must have records verifying
that all persons operating the equipment are certified
all of the following statements about refrigerant compressor are true except
the compressor condenses the vaporized refrigerant.
when the defrost or defog mode is being used all of the following is happening except
the heater shutoff valve is closed
all of the following statements about gauge manifolds are true except
the low side hand wheel is a different color than the low side hose
when refrigerant is removed from the system
the lowering of pressure results in some of the systems components becoming cooler. this component cooling effect makes complete refrigerant removal in a short perdiod of time more difficult.
if a system contains no pressure it is a safe assumption that
the refrigerant has leaked out and one of your first steps in service should be trying to track down a leak or leaks in a system
different hfc 134a systems require use of different oils. you must install
the type and viscosity recommended by the system or compressor manufacturer.to find out the type you need to use refer to the underhood a/c system information label, or look it up in a service manual or electronic information system
standard J2197 HFC 134a service hose fittings
this SAE standard covers fittings intended for connecting service hoses per SAE J2196 from mobile air conditioning systems to service equipment such as manifold gauges, vacuum pumps and air conditioning charging, recovery and recycling equipment. due to similarities between english and metric thread sizes a single unique ACME thread fitting is specified. this fitting was recommended by the compress gas association CGA connection standards committee task force as one which could be qualified to meet their requirements for use and safety in a time frame consistent with the introduction of R-134a.
what is the purpose of an ammeter inductive pickup
to measure greater amperage flowing . the pickup reads the magnetic field created by current flowing through the wire and converts it into an amperage reading.
if a customers arrives with refrigerant in their a/c system a technician removes it then the customer declines any further services the technician must return
to the system the refrigerant it contained when it arrived unless the customer agrees to its removal
the four categories of section 608 certification are
type 1 small appliances type2 high pressure appliances except small appliances and MVACS type 3 low pressure appliances type4 universal all appliances except MVACs
do not mix lubes
use only the type of lube specified by the system manufacture
when recovering refrigerant from any a/c systems continue the recovery process until the system has been reduced from a pressure to a
vacuum
general manuals contain service information about many kinds of
vehicles
as a first step in service always perform a
visual inspection to spot obvious problems. since the service port caps serve as the primary seal for the services ports make sure that each service port in the system has a cap installed and that the caps seals are not damaged. missing or damaged service port caps are major leak sources.
modern antifreeze is made of
water AND antifreeze
repeat recovery process until the vacuum remains stable
without rising for two minutes