A/C test
In a properly operating system, the evaporator temperature is about...
32F
Most experts recommend that the system be drawn down to how many microns?
500 or lower
A "pop" is heard from the radio speakers when the system is operating with the air conditioning on. What is the most likely cause?
A defective compressor clutch diode
A stretch-type AC compressor belt is removed using...
A knife (cut it)
A container of recovered R134a refrigerant has a pressure of 91psi at 80F. This indicates...
A normal condition
A container of R-134a tested at a pressure of 115psi at an ambient temperature of 75F. This means...
Air is in the refrigerant
Most A/C performance tests include Start the engine, measure ambient temperature, or open the doors and set the blower speed?
All
A customer states that the vehicle does not cool as well as it should. Tech A says that the system could be low on charge. Tech B says that a non-functional radiator cooling fan can cause a lack of cooling inside the vehicle. Which tech is correct?
Both
Tech A says a compressor clutch replacement is sometimes possible with the compressor still mounted in the vehicle. Tech B says the compressor clutch can be replaced without recovering the refrigerant first. Which tech is correct?
Both
Tech A says that a quick check of A/C system operation is to feel the temperature of the suction and discharge lines. Tech B says that the suction line should be cold and the discharge line hot after 5 minutes of system operation. Who is correct?
Both
Tech A says that eye protection should be worn when working with refrigerants. Tech B says to avoid skin contact with refrigerants and their oil. Which tech is correct?
Both
Tech A says that new refrigerant oil should be added to new components such as accumulators or condensers as they are installed. Tech B says that two wrenches should be used when tightening most line fittings. Which tech is correct?
Both
Tech A says that the system should be operated after injecting fluorescent dye into it. Tech B says that wearing yellow-tinted goggles can help you find the dye traces, and this also protects your eyes. Which tech is correct?
Both
Tech A says that you should begin HVAC problem diagnosis with a thorough inspection. Tech B says that you can determine from the inspection what type of system you are dealing with. Which tech is correct?
Both
One drawback to using CO2 (R-744) as a refrigerant is...
CO2 system pressures are extremely high
As the refrigerant passes through the condenser, it...
Condenses from a gas to a liquid, gives up latent heat to the air flow, is cooled by ambient air
Pressures are controlled in an orifice tube (OT) system by...
Cycling an electromagnetic compressor clutch on and off as needed and using a variable displacement compressor
Adding a small can of sealant to the A/C system is a good preventive measure to stop leaks.
False
The clutch must be removed and replaced to...
Get access to the compressor shaft seal
O-rings used in R-134a systems are usually...
Green
Increasing the number of slots in the clutch armature helps to...
Increase holding power
Compressing a vapor...
Increases the pressure and increases the temperature
The discharge air temperature is warm or slightly cool. The pressure gauges shown indicate which most likely cause?
Lack of airflow through the condenser
R-134a is in what color container?
Light blue
Most newer compressors use a ... seal on the compressor shaft.
Lip
In an A/C system, the refrigerant changes state from a ... in the evaporator
Liquid to a gas
The discharge air temperature is warm and the pressure gauges are as shown. What is the most likely cause?
Low on refrigerant
Tech A says that retrofitting a system is simply a matter of recovering the R-12 and recharging it with a drop-in refrigerant. Tech B says that the charge level specification is the same with R-134a as with R-12. Which tech is correct?
Neither
Tech A says that the same recovery unit can be used for R-12 and R-134a. Tech B says that the service hoses from an R-134a recovery unit must have shutoff valves within 18 inches of the end. Who is correct?
Neither
Most R-134a refrigerant systems use... oil for lubrication.
PAG
The basic designs of AC compressors include...
Piston, vane, and scroll
The fitting found on an accumulator is for which of the following?
Pressure switch
The SAE standard J2788 requires improved performance from...
Recovery and recycling machines
Most piston compressors use what type of valves?
Reed
One possible new type of vehicle air conditioning system is the .... system.
Secondary loop
Both high-side pressures and low-side pressures are low with the engine running and the selector set to the air conditioning position. Tech A says that the system is undercharged. Tech B says the cooling fan could be inoperative. Who is correct?
Tech A
Tech A says that as the clutch drive hub is replaced, the air gap should be checked at three different places. Tech B says that the air gap is not important as long as the clutch ohms are correct. Who is correct?
Tech A
Tech A says that it is important to position retaining ring correctly when replacing clutch parts on a compressor. Tech B says that the air gap may be adjusted with thick spacers. Who is correct?
Tech A
Tech A says that oily residue on a fitting or hose can indicate a refrigerant leak. Tech B says that this residue is normal around most A/C fittings. Who is correct?
Tech A
Tech A says that pressure checks are one method of diagnosing A/C problems. Tech B says that trouble trees are used only for mechanical problems. Which tech is correct?
Tech A
Tech A says that when the compressor is replaced, the oil levels should be checked. Tech B says that the oil from the old compressor can be reused. Which tech is correct?
Tech A
An automotive air conditioning system is being tested for a lack-of-cooling complaint. Both high and low pressures are higher than normal. Tech A says that the system is low on charge. Tech B says that the system is overcharged. Which tech is correct?
Tech B
Tech A says that a system should be evacuated for twice as long if the vacuum pump will only pull it down to 10"Hg. Tech B says that the system might have a leak in it if it will not pull down into a deep vacuum. Which tech is correct?
Tech B
Tech A says that all O-rings are OK to use with R-134a systems. Tech B says that the color of the O-ring indicates the material it is made from. Who is correct?
Tech B
Tech A says that checking refrigerant odor (HC smell) is a reliable way to check for contaminated refrigerant. Tech B says that refrigerant with more than 2% of a foreign refrigerant normally should be sent off for reclaiming or disposal. Who is correct?
Tech B
Tech A says that mixing small amounts of refrigerant is acceptable according to the EPA. Tech B says that each refrigerant must have unique fittings to reduce accidental mixing of refrigerants. Who is correct?
Tech B
Tech A says that most leaks at line fittings can be stopped by tightening the fitting nut a little tighter. Tech B says that line fitting O-rings should be properly positioned and lubricated with refrigerant oil as they are installed. Which tech is correct?
Tech B
Tech A says that refrigerant charge levels are given in the owner's manual. Tech B says that charge levels are printed on the under-hood decal. Who is correct?
Tech B
Tech A says that vacuum is usually measured in psi. Tech B says vacuum is usually measured in inches of mercury (Hg). Which tech is correct?
Tech B
The first worldwide effort to limit the use of ozone-depleting chemicals has become known as...
The Montreal Protocol
How is the AC compressor lubricated in an R-134a system?
The oil moves through the system simply with the movement of the refrigerant
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)
If an A/C system contains contaminated refrigerant, how can the contaminated refrigerant be moved?
Use a separate recovery machine that is dedicated to contaminated refrigerant recovery
Several different methods of leak detection are available including...
Visual inspection looking for refrigerant oil stains, dye, and using a leak detector
A system has been evacuated and the gauge valves have been closed. A slight increase in pressure after a short time indicates...
a leak in the system
A compressor clutch that cycles on and off rapidly is an indication...
a low refrigerant charge
A/C system flushing uses... to remove contaminants and oil from the system
a special liquid
After an A/C system has been repaired, it can be checked for leaks before charging, using...
a vacuum pump
High-side pressure is affected by...
ambient temperature, fan clutch operation, refrigerant charge level
Rear air-conditioning systems use...
an orifice tube to control the refrigerant flow into the front evaporator and a TXV with the rear evaporator
An automotive A/C compressor is scroll, reciprocating piston, or rotary vane?
any
Switches found on the compressor itself may include a low-pressure switch, high-pressure switch, or low- and/or high-pressure switch
any or all
A vacuum pump removes water from the air conditioning system by...
boiling it
Failure of hoses or fittings in an A/C system can be caused by...
broken engine mounts or loose or missing compressor mounting bolts
A... is used to seal the opening for the compressor drive shaft.
carbon seal cartridge and lip seal
Regulations require any shop performing A/C work to have...
certified personnel, refrigerant recycling equipment
In a correctly operating A/C system, the outlet line from the evaporator should be...
cool
In an operating A/C system, the outlet line from the evaporator should be...
cool
In a piston-type compressor, the pistons are driven by a...
crankshaft, swash plate, wobble plate
A clutchless damper drive is used with what type of AC compressor
electronic-controlled, variable displacement compressor
The TXV is located at the ...
evaporator inlet
In a noncycling clutch system, evaporator freeze-up is prevented by controlling...
evaporator pressure
Some A/C systems cycle the compressor clutch in regular intervals to control...
evaporator temperature
A container of contaminated refrigerant should be colored...
gray with a yellow top
Refrigerant entering the condenser should be...
high pressure vapor
Heat travels from...
hot to cooler
In a system that is operating correctly, the lines and hoses on the high side should be...
hot to the touch
The condenser...
is a heat exchanger, is a device where air passing over it cools the refrigerant and causes it to condense into a high-temperature liquid, transfers heat from the refrigerant to the air flowing
A fixed-orifice tube...
is usually located in the evaporator inlet or line to the evaporator
The compressor in an A/C system is needed to...
keep the refrigerant circulating, make the gas hotter than ambient air, increase the gas pressure
As the latent heat of condensation is transferred to the airstream in the condenser, the refrigerant makes the change into a....
liquid
If both the low side and the high side show low readings, what might be the problem?
low refrigerant charge or leaks
Global warming potential (GWP) is decreased if a gas has a ... GWP number
lower
A musty, moldy smell in the air-conditioning system is usually due to...
mildew-type fungus growth
A faulty A/C system has a high low-side pressure and a high high-side pressure. Tech A says that the system is probably starved. Tech B says that the system has a bad thermostatic switch. Who is correct?
neither
A "starved" evaporator is one that has low pressure but a too warm temperature. This is due to a stuck open TXV, too high refrigerant charge, or restricted air flow over the evaporator?
none
clear water is seen dripping from beneath the vehicle on the passenger side. This means...
normal operation
A compressor speed sensor is used by the HVAC ECM to...
prevent a locked-up compressor from destroying the engine drive belt and to determine if the compressor is running by comparing the compressor and engine speed signals
An air conditioning system may use an inline filter to...
prevent any solids from clogging the expansion valve
A cooling module usually includes what components?
radiator, automatic transmission fluid cooler, and A/C condenser
An accumulator is very similar to a....
receiver-drier
Present standards and good work habits require that recovered refrigerant be...
recycled
An air conditioning system may use a muffler to...
reduce noise
Normal compressor repairs include replacement of the...
reed valves, shaft seal, clutch coil
The advantages of a TXV system over an orifice tube system include...
requires a smaller refrigerant charge
The advantages of an orifice tube system over a TXV system include...
simpler and cheaper to produce
In a reciprocating piston compressor, the pistons are driven by a...
swash plate, wobble plate, crankshaft
Refrigerant can be contaminated with non-condensible gases (NCG) if the...
tech uses sloppy service procedures, system is not thoroughly evacuated before recharging, and recovery unit hose is not tight
Desiccant is placed in the receiver-drier or accumulator-drier...
to absorb moisture from the system
