Poor performance from the Air Conditioning wastes fuel and is a major cause
of A/C compressor failure. The most common cause of poor A/C performance and
compressor damage is too little or too much refrigerant. The proper amount
of refrigerant in the system is very critical to A/C operation. Running the
system low on refrigerant is one of the major causes of compressor failure
as the system lubricant flows with the refrigerant. Low refrigerant flow
means poor lubrication.
If your A/C system works but just doesn't seem cold enough, it is a good
idea to get it looked at sooner than later.
Today's air conditioning systems do not have a way to visually check the
refrigerant level and the only accurate way to get the proper amount in is
to recover the refrigerant, measure it and then put the proper amount back
in. Many times when the A/C system isn't working well, someone may just add
more refrigerant by just "guessing" when it seems to be working fine. It is
easy to get too much in at this time which causes higher pressures and heat,
which causes mileage loss and eventual compressor failure.
Other things that can cause air conditioning performance problems are not
running in "recirculate" in hot weather, cooling fan problems, debris in
front of the radiator/condenser and heater control problems.
We recommend having the system evacuated and refilled every 3 - 4 years as
even a system with no visible leak will lose a little every year.
Tech Tip: Do's and Don'ts of A/C Repair
By Larry Carley
Technical Editor
Autocarepronews
CAUSES OF A/C REPAIRS
A/C compressors are usually the most expensive A/C component to replace,
followed by condensers and evaporators. So its very important to make sure
(1) the compressor really is bad and needs to be replaced, (2) the cause of
the compressor failure has been identified and fixed so the new compressor
does not fail for the same reason, and (3) the new compressor is installed
properly and lubricated with the correct type of compressor oil.
The most common cause of compressor failure is inadequate lubrication. This
may be the result of a refrigerant leak that allows compressor oil to leak
out of the system. Typical leak points are hoses, hose and pipe connections
(O-rings and flange gaskets), the evaporator, condenser or the compressor
shaft seal. Leak detection dye or an electronic leak detector should be used
to find the leak so it can be repaired.
Lubrication problems can also be caused by a blockage (typically the orifice
tube) that prevents refrigerant and oil from circulating through the A/C
system.
Using the wrong type of compressor oil for the application or the wrong
amount can also lead to premature wear and failure. There are various grades
of PAG oil, and using the wrong grade can cause problems. Always use the
type of PAG oil specified by the compressor manufacturer or vehicle
manufacturer. Use only the amount specified for the compressor. Adding too
much oil can cause cooling problems.
Mineral-based compressor oil is only for older vehicles (pre-1995) with R-12
compressors, and should never be used with a compressor in an R-134 A/C
system.
A compressor may also fail if there is sludge or debris inside the A/C
system. Moisture contamination of the refrigerant can form acids that attack
metal surfaces and form sludge inside the system. Over time, this can gum up
and damage the compressor. If the system contains any sludge or debris, the
hoses, evaporator and condenser should all be flushed out to remove the
contaminants. Note: Some condensers cannot be flushed due to the way they
are constructed, so replacement is necessary if the condenser is
contaminated.
A compressor may also have to be replaced if its leaking, making excessive
noise or not working correctly because of an internal valve or piston
failure. Some compressors are naturally noisier than others, but loud
knocking noises can sometimes be caused by air in the system. The cure in
this case is not to replace the compressor, but to recover the refrigerant
from the system, then vacuum purge the system for 30 minutes to an hour with
an A/C vacuum pump to remove the unwanted air. If the compressor is still
making noise after the system has been purged and recharged, it probably
needs to be replaced.
When a compressor fails, it may spew out metallic debris. Most of the junk
ends up in the condenser, but some may travel as far as the orifice tube or
be blown back into the suction hose. If this junk is not flushed out of the
system, it can be sucked into the new compressor and cause it to also fail.
ADDITIONAL PARTS REPLACEMENT
When a compressor is replaced, the accumulator or receiver/drier should also
be replaced. The accumulator or receiver/drier contains a bag of desiccant
that absorbs moisture. This helps to protect the A/C system against sludge.
But, over time, the desiccant becomes saturated and cannot hold any more
water. If the A/C system has been opened up for repairs, or has lost its
charge of refrigerant, humidity in the outside air can enter the system and
overload the desiccant. Thats why it needs to be replaced.
Another component that should be changed when replacing a compressor is the
orifice tube. This small plastic tube meters refrigerant into the
evaporator. If it plugs up, it can block the flow of coolant, causing the
A/C to stop blowing cold air. It can also starve the new compressor for
lubrication because the oil circulates with the refrigerant.
A couple of preventive measures can also be taken to protect a new
compressor. One is to install an in-line filter in the high-pressure liquid
line to catch any debris that might come out of the condenser. Another is to
install an inlet screen filter in the suction hose to stop any debris from
being sucked into the compressor.
Other A/C components that may also have to be replaced when changing a
compressor include the magnetic clutch (if it is worn or slipping), the
drive belt and A/C hoses. Refrigerant that contains leak detection dye can
be used to recharge the system. After the dye circulates awhile, it will
reveal any leaks that might have been missed and need to be repaired.
FIGHTING A/C ODOR
Air conditioner odor complaints seem to keep coming back no matter what
treatment your customers try, right? The reason is that most odor treatments
are short-term, while the source of A/C odor is a combination of factors,
including airborne microorganisms, that naturally repeat over time. Many
products that are offered to control odor, such as disinfectants, may have a
relatively effective initial application. Unfortunately, even the strongest
disinfectant leaves no long-term, residual protection against the inevitable
repeat odor infestation.
CAUSES OF A/C ODOR
Air conditioning odors typically result from uncontrolled growth of bacteria
and other microorganisms in the evaporator. Research by independent
laboratories has found fungi such as Aspergillus, Cladesporium, Penicillium
and others growing on cooling coils and other A/C system areas.
How do these microorganisms get there? They are naturally present in outdoor
air, and are drawn into the evaporator during air conditioner operation.
Moisture also contributes to A/C odor formation. Most of the moisture that
condenses on cold surfaces inside the system drains harmlessly over time.
However, some moisture continues to cling to coil surfaces after the A/C
shuts down. Microbial contaminants in the air combine with this lingering
moisture in the evaporator. The warm, dark and moist conditions in the
evaporator provide an ideal breeding ground for bacteria, mold and mildew to
grow and generate musty odors.
DOWNSIZED EVAPORATORS TRAP MORE MOISTURE
As vehicles were downsized (while also increasing their glass content), A/C
system manufacturers reduced evaporator size while simultaneously increasing
fin count. These densely packed evaporators trap and hold more moisture.
To see this for yourself, dip your hand into a glass of water. As you remove
your hand from the water, quickly spread your fingers apart. No water will
bridge the gap between your fingers. Dip and remove your fingers again, this
time spreading them slowly to only a fraction of an inch apart. Water will
bridge the smaller gap between your fingers, and remain far longer than if
you open your fingers wide.
WAYS TO REDUCE A/C ODOR
Some odor treatments are merely feeble attempts to cover up odor. Almost all
odor treatment products fail to provide a long-term residual effect that can
reduce the recurrence of odor. Here is a brief description of the
performance capabilities of various odor treatments by product type.
Perfumes/Fragrances: Are designed to cover up odor with another, more
acceptable scent. Can be time-release agents. Cover-up perfumes and
fragrances cannot eliminate odor-causing microorganisms.
Disinfectants: Destroy odor-causing microorganisms on contact. The typical
liquid disinfectant quickly evaporates or washes out of the system along
with the condensation that forms during A/C use. The next time airborne
bacteria enters the system, odor can begin again. For this reason,
disinfectants can require frequent repeat application to control odor.
Smoke/Mist Application: Smoke and mist products combine a liquid
disinfectant with a fine spray application technology. The spray is directed
toward air intake vents inside the passenger compartment, so it reaches down
into the air conditioning evaporator, where odor-causing microorganisms
colonize and grow. Ease of application is a plus, but again, the
disinfectant quickly drains from the system, leaving no long-term protection
against odor recurrence.
Air Filters: Catch and absorb particulates and some gases as they pass
through ducts to the passenger compartment. Many filters use activated
charcoal. Filters become saturated or their active ingredient loses
effectiveness over time, and must be replaced. Some filters cannot catch
gaseous odor molecules, which can be small. Filters do not eliminate the
source of odor-causing microorganisms.
Baking Soda/Absorbents: Help absorb moisture, which is needed by
microorganisms in order to grow. Lack of moisture reduces the ability of
microorganisms to multiply and cause odor. Absorbents become saturated
quickly and allow odor to return, thus requiring repeat application.
Chemical Reactants: Reduce odor by combining with molecules of the
odor-causing microorganism. The new, combined molecules must then be removed
(wiped up with a dry towel, washed away in a liquid, etc.) to complete the
odor treatment. Like liquid disinfectants, chemical reactants provide only a
short-term treatment, and can allow odors to return quickly.
Antimicrobial agents: Have a wide range of successful microbial control
applications, from inhibiting fungal growth on boat hulls to preventing mold
and mildew growth in carpet and wall coverings. One unique antimicrobial
product used on mobile air conditioner odor combines its active ingredient
with an acrylic resin that is sprayed into the evaporator. The acrylic resin
dries onto the evaporator coils, forming a coating that sheds moisture
better than uncoated coil surfaces. The antimicrobial agent remains embedded
in the coating, where it kills or inhibits the growth of any microorganisms
that attempt to settle on the coated surface. Together, the antimicrobial
and acrylic resin coating last in the A/C system for up to three years,
protecting against moisture buildup and the growth of odor-causing
microorganisms.
Information provided courtesy of AirSept, Inc.
