2011 05 Ms

A service to members – $70 annually to subscribers © Mobile Air Conditioning Society Worldwide

By Paul Weissler, MACS Senior Technical Correspondent May 2011
A TOUGH DECISION YOU SHOULD MAKE RIGHT NOW
Most independent garages are small businesses closed on sits over the weekend.”
both Saturday and Sunday year-round. At the same time, all These comments may be true, but we should also note that
the franchised shops (quick lube, tires, etc.) are open at least on many dealer parts depart-
Saturday and often on Sunday too (Figure 1). A recent survey by ments also are open on Satur-
Chrysler showed that 72% of its dealers keep their shops open days, and they are selling to
on Saturday and Chrysler is trying to persuade more to do so, more than do-it-yourselfers.
to get that percentage up to at least 80%. It may be important for We’ll also point out that A/C
you to make a decision on whether or not to do the same, just as is a seasonal business, and
the peak A/C service season is starting. there’s nothing that says you
Typical comments we hear about the competition that’s open have to offer full service on
on weekends are: weekends – or for that mat-
• “They just do oil changes, tires and stuff like ter – any other individual
that.” day of the week. With flex-
• “Air conditioning is important and people re- ible hours in such wide use
ally want it when it’s hot, but I need the weekends today, you could have a spe-
off, particularly during the busy season. Remem- cialist off duty on a weekday.
ber, we’re not talking about whether or not the car Some technicians may prefer
starts, runs and stops.” Sunday-Monday off, for ex-
• “Those shops open weekends just have kids or ample.
guys who may be able to do a few simple jobs, but This article is not a clarion Figure 1: Sign at a seven-day opera-
no real technicians there to do real repairs.” And call for Saturday A/C service. tion that, despite the tire company
similar, “All you’re going to get on a weekend is We see car dealers that are logo, offers a wide range of auto ser-
vice and repair. With people working
‘gas and go’ for air conditioning, and we do real sufficiently busy, but have flex hours and changes in lifestyle,
leak detection and repair.” limited service bays, so they weekend (even night) service is tak-
• “We do a lot of general auto repair too. If I open can justify running two shifts ing hold in many areas. If you’re un-
for some types of work, the pressure will be on to every day, or even a 7/24 op- sure if some weekend service, even if
it’s seasonal, is something you need
do more than oil changes and brake jobs. As it is, eration. to offer, start visiting these shops
we schedule very carefully on Friday so we get We would never suggest during weekends and determine if
everything possible out the door. Usually, nothing that to a small independent there’s business worth pursuing.

ALSO INSIDE THIS ISSUE:
ECO MODES—WHAT THEY ARE AND HOW TO TEST THE SYSTEMS .............................................................................. 2
TORQUING WATER PUMP BOLTS ................................................................................................................................................ 5
THOSE HVAC CASE ACTUATORS ....................................................................................................................................................................6

MACS Service Reports is the official technical publication of the the accuracy of the content of MACS Service Reports. MACS,
Mobile Air Conditioning Society Worldwide, Inc., P.O. Box 88, however, will not be responsible for the accuracy of the informa-
Lansdale, PA 19446. The material published in MACS Service tion published nor will MACS Worldwide be liable in any way for
Reports expresses the views of the contributors and not neces- injury, labor, parts or other expenses resulting from the use of
sarily that of MACS. Every attempt has been made to ensure information appearing in MACS Service Reports.

May 2011 1 MACS Service Reports

garage. You and your employees still want to have a life, and if bringing the customer back? The fact that you booked the job on
you offer a reasonable package of convenience and fairly-priced a Saturday is the plus business. However, lots of A/C jobs may
good service to your customers, you’ll do fine. be completed with parts in your stockroom, or if there’s a leak
But hours of operation depend on the service mix in your you can’t find, add a dose of trace dye and tell the customer to
shop, and what competition requires. If you feel there could be a bring the car back on Monday.
marketing advantage to Saturday service and you can work out The economy is still in the doldrums, and being competitive
the flex hours with your employees, you could be the one shop is important. Located in a business district that clears out for the
or the first shop in your area that forces the issue-- and there’s weekends? That makes the decision easy. However, if you pull
nothing wrong with that. If dealers are closed on weekends and from residential districts and want to post Saturday service (per-
parts are near-impossible to get, you could decide otherwise, or haps with an early closing) as a seasonal offering featuring air
stick to a limited range of services. conditioning work, you still are free to change hours of opera-
What’s wrong with taking in an A/C job on a Saturday, find- tion in winter. ■
ing out it needs a compressor you can’t get at that time, and

ECO MODES—WHAT THEY ARE AND HOW TO TEST THE SYSTEMS
The auto industry, facing the 35.5 mpg regulatory mandate affect the way an increasing number of A/C systems operate,
for 2016 (with important “early credits” available since 2009), and that translates into how you troubleshoot a system. You
is doing all sorts of things to reduce the fuel consumption of air have to be able to tell if A/C performance is poor, or if there’s
conditioning. The A/C effect on fuel economy previously did something else in the picture, and the simple “is the air cold”
not affect window sticker fuel economy numbers, because the isn’t so simple anymore. What also enters the picture is the A/C
fuel economy test cycles (city and highway) didn’t run the ve- control system in the supposedly normal mode, which also
hicles with A/C on. Starting with the 2011 model year, all gaso- may use an operating strategy that could be confused with er-
line/diesel engine cars are run through five driving cycles, one ratic performance.
of which includes A/C on and four of which have a lot of idle In other MACS Service Reports, we’ve talked about the
stops. “breeze” airflow strategy of some luxury cars (Audi, VW and
Starting next year, we’ll also be seeing a lot of cars with idle Infiniti, for example), and that clearly is very different from a
stop (a subject whose effect on A/C we’ll cover in a future max-cold blast of high blower speed air from the center reg-
MACS Service Report). But for now, let’s look at the “ECO” isters. The strategy will have a fuel economy benefit (even if
(economy) modes, which are being used on all hybrids in par- small), but there’s also a matter of what the engineers believe
ticular, and some conventional models (Figure 2). In fact, some will deliver a more comfortable level of climate control. After all,
Japanese cars had an air conditioning Economy mode for many a lot of people may not want a heavy blast of cold air to the face.
The new Lexus CT200H is widely considered a custom-body
Prius, and it does have a Prius powertrain, but a lot of differ-
ences too. Most important, it has Toyota’s most aggressive
Denso design in its “neural network” control system for HVAC.
Neural network (Figure 3), for those who’ve forgotten, is a com-
plex algorithm that mimics the human brain’s decision-making
process. It continuously readjusts the importance of sensor and
switch inputs according to each other, so that the A/C system’s
target for A/C register temperature and blower speed depends
on the inter-relationships. In simplest terms, if humidity is high
and the ambient temperature indicates a likely need for defrost,
Figure 2: Most drivers of hybrids (and likely the new electric vehicles
such as the Nissan Leaf) are sure to be using ECO (economy) mode for
any A/C cooling request from the driver is modified accord-
maximum efficiency. If you see the “ECO” on the instrument cluster of ing to what is needed for effective defrost, and if this requires a
this Lexus CT200H, HV performance will be reduced, perhaps below
AC change in the calculated cooling load, the computer calls for it,
what the customer expects. and if necessary may increase the compressor displacement. It
also can vary the temperature between upper and lower regis-
years, a simple A/C module algorithm that with the driver’s ters, so if the solar load is high, the upper registers deliver cooler
push of a button, would change the clutch cycling strategy to air.
increase the cycled-off time. And if you go back to the days of There’s a lot more to it, including the fact that the computer
hang-on units, turning the Cool control knob changed the sens- also controls the output of the engine’s electric water pump,
ing by the cycling clutch switch, which (depending on which so the need for engine cooling vs. cabin heat also must be part
way it was turned) increased or decreased the cycle-off time, for of the strategy. But basically it means that you can’t just think,
less or more A/C cooling. “Well, it should produce colder air and the blower should run
Understanding all these computer strategies – which go be- faster.”
yond just a fuel economy objective – is important, because they Further, this system (like most other late model ones) has a


refrigerant capacity of just 16 oz, which means that any sealing of the cooling is to already cooled interior air, but without the
failure that causes a loss of just a couple of ounces or more can nearly 100% recirculation that would be used with Max Cool.
produce a loss of cooling performance. Also, in part for Federal The recirc level is from a complex computer calculation con-
emissions credits, the systems are changing system refrigerant tinually adjusted according to what temperature air must come
controls. As you should know, evaporator temperature control from the A/C registers. The setting is largely from an efficiency
today may allow the evaporator core temperature to rise into standpoint, within limits that include factors for humidity and
the mid-40’s (or even higher) if the A/C cooling load is low, vs. temperature levels outside and within the cabin.
the conventional system that always cools the evaporator to Combine that with a system that in ECO mode is designed to
“32 degrees F.,” then reheats the air in the plenum to produce reduce A/C cooling below what the motorist called for (mean-
the desired comfort level by an air temperature mix. We’re also ing higher A/C register air temperatures), and you can see the
seeing a continuous use of partial recirculation, so that much potential for an unhappy customer. Your logical question is:

Figure 3: The “neural network” is intended to produce a cabin climate based on how a human brain might analyze different bits of information and make
an overall compromise decision for the most satisfactory overall result. At left are the inputs, which are all computer-evaluated to produce a decision. Their
obvious impacts are tuned up or down, depending on how significant some are for the particular situation. These “decisions” create “target” settings that
are corrected for a satisfactory overall result, such as enough airflow to cover cabin temperature and defrost if needed. This method does make it effectively
impossible for the technician to determine if the non-refrigeration system is working to design intent. He just has to assume it does, if there are no trouble
codes and all the mechanical parts, including HV flap doors, are operating properly.
AC


How do I know what’s normal, what is represented by a refrig- stack (Figure 4). Select LO
eration system problem, or perhaps a drifting sensor or an out- for temperature with me-
of-calibration flap door in the HVAC case? dium blower (the system
When you have a system designed to operate within tight also should be in recirc and
parameters all around for maximum efficiency, the A/C perfor- airflow through upper reg-
mance level that you’ll be required to restore must include that isters). If you can get the
“ECO” mode to the extent possible. After all, the buyer of a hy- performance you expect in
brid with fuel economy numbers of 40-50-plus mpg is not going maximum cool Auto and/
to run the car in regular mode and tolerate a fuel economy drop or an equivalent manual Figure 6: Mongoose scan/reprogram
into some unacceptably low number, like maybe 30 mpg (yeah, mode, that proves the re- tool, based on the SAE J2534 protocol,
that would make for one very unhappy owner). frigeration system works is available for Toyota/Lexus/Scion
So for openers, it comes down to this: Turn off the ECO (Figure 5). As for the auto- and Detroit three makers’ vehicles. It’s
$495 and does both factory scan data/
mode, by just pressing the button at the bottom of the control matic A/C performance trouble codes, and reprogramming, in
in ECO mode, don’t think conjunction with a PC and a suitable
about installing a new con- subscription to the premium level of
trol module unless there is the factory websites. The Toyota one is
supported by Toyota, which includes
a diagnostic routine that tech support.
points to it. More likely
there’s something else involved if performance is weak, such as
sticking flap doors and air leaks.
With these systems, a technician has to rely on the computers
to produce trouble codes, particularly if system performance is
normal in manual mode. The HVAC has bushels full, and some
of them can be displayed through on-board diagnostics in the
HVAC. Many are likely, however, to show up only with a scan
tool that is either equipped with factory software or something
enhanced far beyond “generic.” If you do a lot of Toyota work,
you should consider the Toyota-endorsed Mongoose from
Drew Technologies, covered on the factory website (techinfo.
toyota.com). For $495, you can buy the Mongoose (Figure 6), a
Figure 4: To turn off the “ECO” setting, which reduces Climate Control pass-through device that uses the SAE J2534 protocol for scan
performance for fuel economy, press the knob at the center bottom of the
control stack. To restore “ECO,” turn the knob to the left.
data and reprogramming.
For $1000, you then can sign up for a year (or $55 for just two
days) of subscription to Toyota’s Techstream Lite, which will en-
able you to search the website for service information, and also
reflash modules (the information system alone is just $15). It’s
one of the best deals around, although Drew does make Mon-
gooses (yes, that’s the plural) for other makes, including Ford,
GM and Chrysler. Each Mongoose services only one make (the
Toyota unit covers Lexus and Scion too, just as the Ford unit
covers Lincoln, and the Chrysler unit covers Dodge). So if you
are a specialist with volume in just one or two makes, it’s a cost-
effective investment. All the electronics are built into the end of
the cable. Yes, you need a shop PC that isn’t ancient – at least
Windows XP, and with a minimum of 512 kb of RAM, but most
PCs built in the last half-dozen years surpass that level. The sub-
scription also provides access to tech support for the informa-
tion/scan/programming system, plus Identifix Direct-Hit (and
one call-in assist) for diagnostic help, but just on Toyota products
of course.
An important thing to be aware of – A/C control customiza-
Figure 5: The best way to evaluate cooling capacity is to check perfor-
tion – example: Even the Lexus CT200H normal mode for set
mance with the system in a manual mode (including recirc and LO set- temp or ambient temp could be set for plus/minus 2 degrees
ting on the temperature dial) and a medium blower setting. You also can C (plus/minus 4 degrees F) from the display, if that was preset
do this in Auto and in addition, in LO setting, which checks some of (double effect possible). Or the blower speed could go up in de-
the automatic control, but without all the neural network adjustments.
frost, or ECO drive operation could be cancelled when the A/C
is turned on (interesting one to keep in mind). ■


TORQUING WATER PUMP BOLTS
When was the last time you replaced a water pump and pounds.
torqued the bolts to specifications – in stages—with a torque Now let’s look at the
wrench you knew was reasonably accurate? We’re not going to water pump issue. Gen-
take a poll using a lie detector, but we suspect few readers could eral Motors has released
honestly answer yes to all three parts of that question. And now a bulletin that says a re-
we’ll add a fourth: in the correct sequence. quired torque sequence
Most reputable tool suppliers offer torque wrench calibration applies to their “high
service, and they sadly aren’t deluged with business that we’ve feature” V-6s (the 2.8, 3.0
heard. Worse, we’ve seen torque wrenches, those big click-off and 3.6-liter engines with
micrometer – set types, tossed into a toolbox after use (well, at dual overhead cams and
least someone had the idea of using it). It’s supposed to be set typically variable valve
Figure 9: Lower intake manifold gasket
back to zero after use, so the timing). Note the sequence, torque sequence for 3800 V-6.
preset spring inside can relax, which is tightening bolts a
rather than take a set. And if star-alternate way, some-
you haven’t used it in a week what similar to road
or so, set it to some reason- wheels. The spec torque
able torque (maybe 50-75 is relatively low, so GM
foot-pounds on a 0-150 range says you can tighten
wrench) and torque a few to 12 N-m/106 inch-
bolts before you take it to the pounds (9 foot-pounds)
job. and then just repeat that
The beam-type torque torque, in the same se-
wrench is low-cost and unless quence (Figure 7).
Figure 7: GM’s recommended mishandled, retains accuracy The sequence was Figure 10: Upper intake manifold gasket
sequence for tightening water for a long time, but it just isn’t instituted to reduce gas- torque sequence for 3800 V-6.
pump bolts on their “high-fea- convenient to use. Working ket leak issues on these
ture” DOHC V-6 engines (2.8,
3.0 and 3.6 V-6s).
on cars means setting torque all-aluminum engines. Of course, precise torque is meaningful
when you can’t see a dial, only if the gasket was mounted on a cleaned surface and the bolt
so the click-off is the almost universal choice. However, if your holes are all clean and dry.
click-off type has taken a beating and you want to check it, you
can tighten a bolt with the beam wrench and see if the click-off And Those Intake Manifold Bolts
type matches it. That’s not perfect, but at least it isn’t total guess- Replacing GM pushrod V-6 intake manifold gaskets is a com-
work. mon cooling system repair, and here again, proper torquing of
There are electronic torque wrenches (well, the electron- the manifold bolts is important for sealing with the new gaskets.
ics measure a strain gauge) and they hold accuracy better, but The bolts on the 60-degree V-6 engines are not reusable. Those
aren’t cheap, and even they don’t like a beating. The enclosed on the 3800 90-degree V-6 are reusable (Figures 8, 9, 10). The
split-beam torque wrench is a choice if you have a technician or sequences, similar to
two who doesn’t treat these tools as well as he should, including cylinder heads, are
the fact that they don’t have to be reset to zero. Although few center-start and then
torque wrenches are accurate at the ends of the scale, the Preci- work alternately to
sion Instruments one is rated for plus/minus 4% from 20-100 foot the ends.
In the case of the
60-degree V-6, not
only do you have to
torque to the specific
sequence, but like
Figure 11: Lower intake manifold gasket
road wheels and cyl- torque sequence for 60-degree V-6 (3.1 liter
inder heads, in two shown). At first, all bolts should be torque to 7
stages, and to two Newton-meters (62 inch-pounds). Then bolts
different torques (one 1-2-3-4 should be tightened to 13 N-m (9.5
foot-pounds), and 5-6-7-8 should be tight-
spec for each set of ened to 25 N-m (18 foot-pounds). All intake
four bolts) to ensure manifold bolts on the 60-degree V-6s should be
Figure 8: “Torque to specifications” is important when replacing intake
good sealing (Figure replaced. The upper intake manifold bolt tight-
ening sequence is similar, but all bolts should
manifold gaskets on GM pushrod V-6 engines, such as this 3800 90-de- 11). ■
be tightened to 25 N-m (18 foot-pounds).
gree V-6.


THOSE HVAC CASE ACTUATORS

The temperature (blend-air) door actuator on the 1997 The wrong part being a perfect-fit replacement for the
Buck LeSabre was clearly not moving, despite the fact right one is no enormous surprise. But with HVAC case
that it was a brand-new one that replaced one that verifi- actuators, the situation can work in a number of ways.
ably had failed. The actuator was a typical General Mo- Here’s an example from a 2000 Honda Accord, where
tors five-wire type, like the type also used by Ford, in the onboard diagnostics (which can be run through the
which two wires form the five-volt reference signal, two HVAC control panel) had logged a code for a failure in
the reversible 12-volt signal to operate the motor and the temperature door control linkage, motor or door it-
one for the motor position feedback signal (Figure 12). self. Okay, the technician finds the motor is seized, or-
The technician found 12 volts on the No. 10 terminal and ders a replacement and the new one doesn’t work either.
varying voltage at No. 8. He looked for a ground at No. Same basic problem as previous: the wrong part, in this
7, but there was nothing. No, it wasn’t a wiring problem, case the recirc door actuator was sent instead of the tem-
but the wrong actuator, as he realized when he removed perature door unit, and the correct part works fine. The
it and took a close look inside its connector: no terminal tipoff: the recirc motor is physically the same, but uses
for B7. just three of seven terminals, whereas the temperature
motor uses five.
The designs in which an actuator is exactly the same
for all case applications, but the harness wiring connec-
tors (although shaped to make the attachment) have dif-
ferent wiring, is an engineering approach you’ll also see.
You’ll have to check the wiring diagram to pick up this
type, and of course, there’s conveniently just one part
number for the dealer to stock.
And then there are the cases in which the actuators
and harness wiring connectors are the same, but because
they are wired to specific terminals of the HVAC control
module, they can be operated in a similar manner but
controlled specifically for the HVAC application. Figure
13, from a 2009 Ford Mustang, is an example of this, and
in fact, the temperature (blend-air), mode doors and de-
frost actuators all are the same part number. For instal-
lation reasons, many of the GM five-wire actuators are
different part numbers.
At Chrysler in all recent years, virtually all the actua-
tors have been the same, so there’s full interchangeability
among the blend-air (temperature), mode-air and even
the recirculation-air door actuators (Figure 14). Each one
is not only the same, but so is the physical housing, a
black molded plastic with a built-in wiring connector,
and they are a two-wire type.
The actuator’s output shaft is also the same, down to
the splines that go into the flap door linkage. Ditto for
the mounting tabs with which the actuator is held to the
HVAC housing (Figure 15).
Even nicer: None of these actuators has to be indexed.
The HVAC control module exercises each actuator and
calibrates it into the required position.
So the Chrysler product line actuators are both revers-
ible and almost infinitely variable. The computer goes
through pulse counting until it finds each flap door’s
stop at one end, then reverses direction (by changing
motor polarity) to find the opposite end. In the case of
Figure 12: Five-wire actuator for General Motors HV AC. Although the
housing may be different for packaging purposes, the internal arrange-
the recirc door, the computer has to provide only two
ment is similar for all, a two-wire five-volt reference circuit, a two-wire positions, although we eventually may see the computer
circuit for the 12-volt actuator motor, and a feedback position wire. provide some intermediate steps for improved tempera-


ture control by mixing cabin and outside air. The mode ditions, the problem is not in the actuator motor itself, a
door actuator, of course, can be stopped in positions for point not to forget in the haste to get a job done.
up to three doors (floor, panel and defrost/demist. The All the operation and positioning is software in the
single zone systems have just one blend-air actuator; the computer, with readings from the sensors. There are
dual-zone (side-to-side) have separate ones. no adjustments and no repairs, so if the actuator motor
Not surprising, the two-wire system works by pull- doesn’t work and the connections to the two-wire sys-
ing voltage low on one side and high on the other, to tem are good, you have to check voltages to the actuator,
cause movement in one direction or another. However, and then the appropriate sensor inputs, before you just
if the voltage is the same along both wires, the motor pop for a new part.
will stop—that’s the way it’s supposed to happen. If it’s Because it’s all software-determined, what you first
working, but not the way it should for the operating con- can do is look for trouble codes, provided of course,

Figure 13: Five-wire actuators in 2009 Mustang HV are not only internally similar but the same part number. Here too, there is a 12-volt motor circuit,
AC
five-volt reference circuit (“VREF”) and a feedback line back to the HV control module.
AC


your scan tool can read these manufacturer-specific tion, which could be a binding door, of course.
codes. The factory scan tool has the software, and it’s up • Moves too far, which could be a door with
to individual aftermarket scan tool companies to add it stripped links or cracks in the linkage or may-
to their tools’ capabilities. From there, diagnosis comes be defective stops.
down to ensuring that if there’s a short or open, you Because door movement problems can cause perfor-
trace the wires, find and fix. The only significant alterna- mance issues, either of the movement errors also could
tive codes are: be a software issue, and you should be checking for an
• Failure to move enough, to a specific posi- update. ■

Figure 15: Chrysler two-wire actuator is as
close to a one-size-fits-all as you’ll find. Even
the motor splines and mounting tabs are the
same.

Figure 14: Chrysler HV actuators are two-wire type, so the control module counts pulses to determine
AC
position and reset the flap door to a new position as required. Note that in addition to the specific driver
terminal for each actuator, there is a common driver for all, to a single terminal, and that in addition to mode
and temperature door actuators, the two-wire design is also used for the recirculation door.

MACS Service Reports is published monthly by the Mobile Air Conditioning Soci- Mobile Air Conditioning Society Worldwide
ety Worldwide. It is distributed to members of MACS Worldwide and is intended P.O. Box 88, Lansdale, PA 19446
for the educational use of members of the automotive air conditioning service Phone: (215) 631-7020 • Fax: (215) 631-7017
and repair industry. Suggestions for articles will be considered for publication, Email: membership@macsw.org • Website: www.macsw.org
however, MACS Worldwide reserves the right to choose and edit all submissions.

Editors: Elvis Hoffpauir, Paul DeGuiseppi
Production Designer: Laina Casey
Manager of Service Training: Paul DeGuiseppi


2011 05 Ms

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