The Hot News
Service and repair options for today’s sophisticated a/c
systems are increasing. Our 2003 MACS convention report
provides the information you’ll need to make the right choices.
‘‘R
eality Check 2003” was the theme of the Mobile Air Conditioning
Society (MACS) Worldwide convention and trade show held recently in New Orleans. And it translated into real-world answers
for technicians’ tough service and diagnostic questions.
This report can’t be a substitute for being there, of course. However, we can fo-
cus on some important a/c service questions that surfaced at the show and, hopefully, give you enough new information to help you do a better job. For example:
•Do a/c sealers really work, or are
they possible trouble?
•Why am I having trouble finding
leaks? Am I doing something wrong,
or do I have the wrong equipment?
•Why do I hear about so many compressor failures, then repeat failures?
What’s really going wrong with them?
26
April 2003
Should I stick with brand-new only?
•Is there one oil I can use in all R134a systems?
A/C Sealers
The short answer to the a/c sealer
question is, they may work and, yes,
they also may be some trouble. There
are two types of sealers—stop-leak
for perforation leaks and seal sweller
for leaking O-rings and O-ring type
gaskets. They’re often combined in a
single product.
M OTOR has recognized that the
stop-leak type may seal small pinhole
corrosion leaks in evaporator cores.
in A/C Service
BY PAUL WEISSLER
On older vehicles where evaporator
replacement is a high-dollar job,
that’s appealing. Evaporator replacements typically cost $800 to $1000,
while some can run as high as $3000.
Pinhole sealing is a valuable function. But there’s no evidence that
stop-leak will seal anything else with
any reliability, whether it’s cracked
welds or a bad compressor shaft seal,
or even severe pinhole leakage from
the evaporator. Because the sealer
works by reacting with moisture in
ambient air, it also can produce
clumps that restrict refrigerant flow,
if there’s enough moisture in the system. In addition, the seal sweller in
some sealing products could distort
some O-ring materials.
Several makers of refrigerant recycling equipment, including RTI, have
reported problems with plugged solenoid valves. Skye has experienced
problems with excessive swelling of Oring seals. At this time, we’ve seen bulletins from Skye, RTI, Visteon, Ford,
Delphi Harrison, Four Seasons and
NAPA warning about voided warranties if there’s evidence of sealer use.
Skye will be changing its machines’
O-ring seals for resistance to swelling
problems. It also has been working
with AirSept (maker of a/c service
kits) to develop a separator/filter for
the inlet to the recycling machine.
The AirSept device, which is in final
testing, is intended to remove virtually all types of debris (including sealer
clumps), plus oil, dye and seal sweller
(typically an industrial alcohol such as
methyl chloride). Eventually, the filter/separator, which connects to the
inlet hose, will be marketed for all recycling machines.
In addition, Neutronics, maker of
electronic refrigerant identifiers, in-
troduced an R-12/R-134a systems
identifier for stop-leak sealer. But it’s
based on inexpensive “mechanical”
technology: Does anything in the refrigerant (e.g., sealer) plug a small,
tortuous path that has been wetted
with plain water? The identifier consists of a fixture attached to the highside service valve that holds a fitting
with the small, twisty flow path, and a
flowmeter at the outlet of the fixture.
The technician watches for three
minutes as the flowmeter reading rises, in part from water being pushed
through, to a peak in about 60 seconds. A drop of more than 40% from
that peak after another two minutes
means the fitting has been restricted
by sealer. The test fittings are discarded after use; other parts, including the flowmeter, can be cleaned.
The amount of refrigerant loss is insignificant, and within EPA-legal
April 2003
27
THE HOT NEWS IN A/C SERVICE
28
April 2003
similar seals? The best-selling cars—
Honda Accord and Toyota Camry—
are among those with the lowest
evaporator replacement times (under
two hours), and reasonably priced re-
placement parts are available.
That said, we know there will be
“exceptions”—good customers who
have a car for which they might not
want to invest in major a/c repairs. In
such cases, first confirm that an evaporator has pinhole corrosion leakage,
and that the value of the old vehicle
cannot justify replacing the evaporator. How can you tell? Trace the
leaks. Sure, that costs money, but as
we said earlier, a professional can’t
just pour sealer into a system and
hope it stops any and all leaks.
Tracing Leaks
Photo: Paul Weissler
guidelines for testing.
Even if you personally don’t use
sealers, out there in the real world
they’re being sold in high volume. Because some are promoted for preventive maintenance, they may well be in
a customer’s car. And although there
are some sealers with labels for underhood application, don’t bet on finding
one. So identifying systems with sealer
not only helps you with a diagnosis
(such as for restrictions and possible
damage to the compressor), but also
helps protect your recycling machine.
Protecting your recycling and other
equipment with a filter/separator
and/or identifier is one aspect of the
sealer issue. Can you do anything with
a system that has been restricted? The
answer may be yes, if you can flush
the system, particularly hoses, evaporator and condenser. But ordinary
flushing agents won’t work, and you
still need an operable compressor.
Visteon’s Reno Faruggia, who
raised the sealers issue at last year’s
MACS convention, worked with suppliers to develop a flushing system to
remove sealer from systems. Visteon
selected RTI to introduce a new terpene flush and a continuous-loop airoperated flushing machine to remove
sealer from the evaporator, condenser
and hoses, along with dirty oil and
debris from compressor and desiccant bag failures. The flush
and machine are in addition
to the Bright Solutions terpene flush and the Cliplight
machine that Visteon and
Ford approved (and made
available to dealers) before
the sealer issue surfaced.
RTI says you can use its new
flush in a Cliplight machine.
Or the Bright Solutions flush
can be used (for other than
sealer removal) in the new
RTI machine.
No a/c professional should
ever attempt to use these
sealers as a cure-all, or a substitute for finding leaks and
replacing the parts involved.
Do you really want to hope that a
sealer product will plug leaks and just
slightly swell shrunken O-rings and
This looks like any 12-ounce can of
refrigerant, but note the words “With
Leak Sealer” on the label. The motorist may have added sealer to his
system without realizing it, or think
the added sealer is an extra feature.
This end view of a solenoid valve from
an RTI machine convinced the company to issue warnings about sealers.
You’re having trouble finding leaks?
No surprise, because today’s vehicles
have packed powertrain compartments and, in many cases, underbody
lines to rear HVAC systems. But it’s
neither rocket science nor pure luck.
Top technicians report they find the
leaks almost every time. Their not-sosecret “secrets”:
•Use an electronic leak detector
that meets the SAE J1627 standard
for sensitivity, and follow the specified procedure in SAE J1628 (including moving the probe 1 to 2 inches
per second and encircling all refrigerant line joints).
•Maintain the detector, which includes replacing the filter in the tip,
and keeping the tip out of oil, coolant,
washer solvent, etc. If the detector pump inhales a slug of
liquid, the detector definitely
will misbehave.
•Be patient. Don’t just
crank up the sensitivity of a
heated-diode/triode/pentode
type detector (or pour in
dye) because you didn’t find
the leak right away. Check
the refrigerant circuit a second time. If the detector’s
setting is too sensitive, it may
false-trigger more often.
A shaft seal also could have
an active leak that occurs only
when the system is running. If
you can’t get the detector’s
probe close enough without
physical risk, shut the engine off and
probe immediately.
For the really tough leaks after-
THE HOT NEWS IN A/C SERVICE
orator lines and use a vacuum pump
and adapters to pull a vacuum on the
evaporator. The evaporator should
pull down to 29 inches of vacuum,
then hold within 5 inches (no lower
than 24 inches) for at least five minutes. If the evaporator won’t meet
those criteria, the leak is too large. A
sealer may reduce the loss for a
while, but that’s it. The expansion
valve is in the HVAC case with the
evaporator on many vehicles, so you
really want to confirm the leak is
from the evaporator.
In the case where a customer has
an old car he plans to keep no more
than two years or so and you’ve confirmed a small leak from evaporator
pinholing, with the cost of evaporator
replacement close to or more than
$1000, you’ve got a possible candidate for sealer. Fine, but you’ve got to
protect against sealer clumping and
damage to the system. Some sealer
kits contain a drying agent, but installing a new accumulator or receiver/dryer offers some long-term protection for the system, as the customer may eventually decide to keep
the vehicle longer than two years.
Get him or her to sign a release for
This hose from a Robinair machine was cut
open and found to be plugged with sealer.
unit comes with a conventional light
and a UV light, so you can insert it
through the evaporator drain and see
if there’s an oil film or an external dye
stain. Other new helpers in this area
are an electronic leak detector with a
UV light built into the tip and several
ultra-compact lights, including a
flashlight type and even one built into
an inspection mirror.
If you’re looking to pinpoint an
evaporator leak, disconnect the evap-
Photo: Paul Weissler
ward, there’s trace dye (often installed at the factory) and ultraviolet
lights made super-slim and compact,
using new-generation LEDs. But
trace dye means the customer has to
come back, so a repeat with the electronic sniffer should be done next, if
there isn’t dye already in the system.
Can’t get an electronic “sniff”? To
make it easier to find evaporator leaks
by looking for dye or oil stains, use an
inexpensive borescope. Robinair’s
Neutronics’ low-cost sealer identifier (about $150) uses a wetted fitting inside a coupling that attaches to the high-side service valve. If the flow path in
the fitting plugs with sealer, the flowmeter reading will drop significantly.
30
April 2003
RTI’s new air-operated flushing machine was developed in cooperation
with Visteon. It’s similar in operation
to the Cliplight Flashworks, which is
also approved by Visteon and uses a
pump f lush circulation cycle followed by a shop air purge.
the work, and be sure to put a warning label under the hood. And shrinkwrapping the service valves to prevent an additional dose of sealer,
more refrigerant, etc., wouldn’t hurt.
Compressor Failures &
Repeat Failures
Compressors are big-ticket items that
can fail when they’re original equipment in a new vehicle, when they’re
remanufactured or even when they’re
all-new replacements. Is something
wrong with all these compressors?
The fact is they’re better than ever—
lighter, more efficient, better-performing—but they’re also less forgiving, particularly in R-134a systems.
These days, a/c is standard equipment even on entry-level econoboxes,
which is why a/c service is such big
shop business today. The sheer volume drives up the number of failures,
even if the failure rate is not abnormally high. The systems are integrated
with the defrost and heat functions,
with electronic controls even on socalled manual systems. This greater
complexity makes diagnosis more difficult, and explains why NTF (No
Trouble Found) is the most common
label put on returned compressors.
Is there one development that
stands out? Well, R-134a makes compressor lubrication more difficult, because the synthetic oils don’t mix
nearly as well with the refrigerant as
mineral oil did with R-12. And we
now don’t have a refrigerant with a
chlorine atom, which produced a lubricationlike surface on moving parts.
These are major factors in the “less
forgiving” category.
But there’s more. The variable-displacement piston compressor (or variable-output scroll) can be tough to diagnose, because it has to be loaded to
force it to pump for maximum cooling.
The situation is getting tougher, as systems with constant-run compressors—
no compressor clutch—are coming into wider use. These compressors rely
on resetting to minimum displacement
instead of disengaging the clutch.
MOTOR has talked about compressor
failures for years, and this year’s MACS
convention seminars on compressors
produced new evidence of some of the
same problems. And whenever we
think we’ve identified all the issues,
along comes new information. The
compressor seminars did make some
points well worth mentioning:
At the top of the list: A “just-low”
refrigerant charge (typically a 10% to
20% undercharge) significantly re-
duces oil flow, according to Four Seasons’ Jim Johnson. He gave this example for 88°F ambient: The a/c duct
temperature rose just 3° (from 46° to
49°F), hardly enough for a customer
complaint. Yet so much oil was
trapped in the evaporator under lowrefrigerant conditions that oil circulation dropped from about 10% to 25%
April 2003
31
THE HOT NEWS IN A/C SERVICE
32
April 2003
Probe
Sensor
Tip Protector
Filter
The tiny filter in the tip of an electronic leak detector should be replaced at
least once a month, or anytime it becomes plugged with water or oil. It’s the
sensor’s only defense against damage. In this design, the heated sensor is in
the probe tip just behind the filter; in others, it’s in the detector body.
vents—including WD-40—were being used, and the results aren’t pretty.
ACDelco’s Bob Stewart said his studies show that 8% of brand-new service compressor failures can be
traced to the use of flushing agents.
The major reasons for using remans are price and availability, with
the latter increasingly important.
There are so many compressors out
there that even shops with customers
willing to pay the new-pump price
are using remans, because that’s what
they can get. The quality of remans
from major suppliers is high, but you
can’t put them into a dirty system and
expect them to survive the abuse.
That’s why replacing plugged con-
Photo: Paul Weissler
by weight to just 2% to 4%. That’s a
prescription for increased compressor
wear and therefore short compressor
life. Other causes of similarly low oil
flow, he said, are internal restrictions
(typically from contamination, which
increases rapidly with low refrigerant), poor airflow through the condenser and high coolant temperatures.
Today’s systems have R-134a refrigerant capacities as low as one
pound (Saturn Ion), so as we’ve noted
in previous a/c reports, just 2 to 3
ounces lost and the system is in trouble. Even the larger systems have capacities under 2 pounds. And although large SUVs with rear a/c may
have a lot more, they’ll still be perhaps 3 to 4 pounds, a capacity we
used to see on R-12 systems in passenger cars.
What all this means is that you need
very accurate measuring equipment—
pressure gauges and thermometers—
for the right diagnosis, and charging
equipment to install exactly what’s
specified. Just because your charging
equipment is calibrated to .1 pound or
even 1 ounce, that doesn’t mean it’s
charging refrigerant that accurately.
When was the last time you
checked—even a digital scale? Is your
equipment old or damaged, and badly
in need of replacement or repair? In
previous a/c reports, we’ve shown
what neglected, damaged equipment
looks like. Hopefully, you’re getting
the idea (or look at previous April a/c
issues at www.motor.com).
Another important point made at
this year’s compressor seminars is
that new vs. remanufactured continues to be a controversial issue. Sure,
brand-new compressors have a lower
failure rate than remans, but that’s
because they start out as original
equipment in clean systems. Remans
never do. Although new compressors
also have a lower failure rate for replacement, they also don’t fare as well
in debris-filled systems. And all compressors do poorly if a system is
flushed with an unapproved agent
that’s not fully purged from the system. MACS trainer Jim Brunner told
the convention that petroleum sol-
Robinair’s Flex-View UV 3591 borescope has both a UV leak-detection light for
dye traces and a conventional inspection lamp in the tip. When inserted
through the evaporator drain, the borescope permits inspection of the evaporator core for leakage and fungus contamination.
densers, orifice tubes, accumulators
and receiver/dryers, flushing in some
cases and using in-line filters are important service items.
The MACS trade show also unveiled many lines of brand-new compressors, including direct replacements for the most popular Delphi
Harrison and Denso models. Some
are made here by aftermarket companies such as Four Seasons and CompressorWorks, or imported by aftermarket suppliers from Japan and China. Even Zexel/Valeo, looking to increase its aftermarket business, is
producing replacements for popular
Delphi Harrison axial six-cylinder
models. And Sanden long has supplied the Chrysler Group with replacements for the discontinued
C171 axial six-cylinder compressors
(which also are manufactured new in
China and sold here). In addition,
such companies as ACDelco, Visteon
(Climate Pro) and Frostemp (Coolstar) sell comprehensive lines of OEbrand new compressors.
The replacement compressors are
designed to bolt in place of the OE
units and offer similar performance,
even if the physical look and internal
operation are totally different.
some owner’s manuals suggest higher-viscosity engine oils in summer
and ultra-lights for easier starting in
winter. To add to the confusion, many
motorists want “higher-mileage oil,”
“oil for SUVs,” etc., so shops have to
stock them, too.
The R-134a a/c situation actually is
much more stable, and we’re down to
four oils—light (typically 46 centistokes, or CSt), medium (100 CSt),
heavy (typically 125 to 135 CSt) and
extra-heavy (150 CSt), despite proprietary formulations. Now it seems that
lightweight oil will be acceptable for
most compressors, at least for topping
up (a 2- to 3-ounce addition that may
accompany replacement of a com-
Compressor Oils
When R-134a replaced R-12, every
system manufacturer had its own oil,
and often more than one. To follow
each maker’s guidelines, a conscientious shop needed a shelf full of different oils.
Why can’t we have just one a/c oil?
technicians moaned, and gradually
the number of oils came down. The
OEMs and most remanufacturers all
had settled on polyalkylene glycol
(PAG), although a handful approved
polyol esters (POEs), primarily for
retrofit. But even among the PAG
proponents, there was no agreement.
Of course, we have about a dozen
engine oils and no one complains.
But so long as an engine oil is designated for API Service SL, it meets
the carmakers’ guidelines, right? Not
really, as some makes mandate full
synthetics, or gas-conserving and/or
specific-viscosity oils. And, of course,
April 2003
33
THE HOT NEWS IN A/C SERVICE
subishi, Zexel and Visteon. GM approved the 46-CSt oil from Idemitsu,
the oil supplier to Visteon and reportedly most Japanese compressor manufacturers. The 46 is being used for
Photos: Paul Weissler
pressor, evaporator or condenser).
The “universal oil” approach is taken by General Motors, which has
been using compressors made by Delphi Harrison, Denso, Sanden, Mit-
The Inspector flexible-shank leak detector from Mastercool combines a
corona-discharge electronic probe with a UV light for locating dye traces.
Tracer Products’ new UV lamp is situated on the end of an inspection mirror
with a telescoping shank that extends up to 28 inches.
34
April 2003
factory installation on all but Delphi
compressors, and GM will be marketing this oil to its dealers. It’s the service oil for all GM R-134a systems,
except those retrofitted from R-12.
GM’s okay for 46-CSt oil basically
sets a de facto standard for almost all
compressors, within some limits.
Some rotary vane compressors (such
as the Denso TV in some Toyotas)
call for a specific oil.
And then there’s Delphi Harrison.
The new Delphi CVC-6, CVC-7
(compact variable compressor, sixand seven-cylinder, introduced in
2001) are factory-filled with oil from
a U.S. supplier (Union Carbide), and
shipped to both GM and the aftermarket. This oil has a viscosity of 55
to 65 CSt, but that’s close enough to
the 46-CSt oil used in other GM
compressors, and Delphi has no objection to substitution with the 46CSt oil. That’s important, because
GM’s first approval of the 46-CSt oil
for service started in 2002 and applied to 2002 Chevy Cavalier, Pontiac
Grand Am, Olds Alero and Pontiac
Sunfire cars with the 2.2L four-cylinder engine, and that engine has a
CVC-6 or CVC-7.
The older-design Delphi Harrison
compressors (H-6 axial six-cylinder,
V-5 and V-7 variable displacement
compressors, and R-4, still manufactured for service) also are used by
GM. For these Delphi specifies the
125- to 135-CSt oil, but allows a topping up with the 46-CSt. However, if
a GM system requires at least 50% or
more of a fresh fill—i.e., 4 ounces or
more—then the heavier oil should be
used, Delphi cautions.
In the real world, we suspect the oil
situation will come down to this: 46
CSt will be going into all brand-new
compressors except the older-design
Delphis (H-6, V-5/V-7 and R-4). Remanufactured versions also will get
the 125- to 135-CSt oil, and so will
top-ups on older compressors (of all
makes) that are somewhat noisy. Other remans will be lubed with a factory
fill chosen by the remanufacturer, and
if shipped dry, will get whatever is on
the shop’s shelf. The 100- and 150CSt oils are likely to fade.
THE HOT NEWS IN A/C SERVICE
Mercedes and Volkswagen
are beginning to use Denso
variable-displacement
compressors that have no
electromagnetic clutch. If
the compressor seizes, the
elastomeric “doughnut”
disengages from the hub as
shown, and the pulley
rotates freely. Although the
compressor can reduce
displacement to under 10%
and is designed to hold some
oil, it’s still susceptible to
low-refrigerant damage.
Denso Swash Plate Compressor
A/C Compressor Regulator Valve
Hub
Coupling
NORMAL
Pulley Drives Hub
OVERLOAD
Coupling & Hub Deform,
Drive Pulley Slips
Photo courtesy ACDelco
MACS Coolant Panel
Residual amounts of unapproved flushing agent left in the system are unapproved
for a good reason, as this photo of a GM compressor shows. Varnishlike deposits
caused the compressor to malfunction. No, it wasn’t approved for warranty.
36
April 2003
Many attendees at the 2003 MACS
convention with questions on cooling
system problems got the opportunity
to quiz the top tech people. A MACS
panel included chemists from three
leading antifreeze manufacturers,
representatives of two top makers of
radiators and heater cores, the head
of the country’s top coolant test laboratory and even a top authority on
heavy-duty cooling systems. Some of
the panelists’ answers on leading
causes of failures are sure to surprise
you. But you’ll just have to wait for
MOTOR’S cooling system report in the
August issue for the details.
Visit www.motor.com to
download a free copy of this
article. Copies are also available
by sending $3 for each copy to:
Fulfillment Dept., MOTOR Magazine,
5600 Crooks Rd., Troy, MI 48098.
Illustration courtesy Volkswagen
Pulley