2011 05 Ms

MACS Service Reports is the official technical publication of the Mobile Air Conditioning Society Worldwide, Inc., P.O. Box 88, Lansdale, PA 19446. The material published in MACS Service Reports expresses the views of the contributors and not neces-sarily that of MACS. Every attempt has been made to ensure

the accuracy of the content of MACS Service Reports. MACS, however, will not be responsible for the accuracy of the informa-tion published nor will MACS Worldwide be liable in any way for injury, labor, parts or other expenses resulting from the use of information appearing in MACS Service Reports.

May 2011 1 MACS Service Reports

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Most independent garages are small businesses closed on both Saturday and Sunday year-round. At the same time, all the franchised shops (quick lube, tires, etc.) are open at least on Saturday and often on Sunday too (Figure 1). A recent survey by Chrysler showed that 72% of its dealers keep their shops open on Saturday and Chrysler is trying to persuade more to do so, to get that percentage up to at least 80%. It may be important for you to make a decision on whether or not to do the same, just as the peak A/C service season is starting.

Typical comments we hear about the competition that’s open on weekends are:

• “They just do oil changes, tires and stuff like that.”• “Air conditioning is important and people re-ally want it when it’s hot, but I need the weekends off, particularly during the busy season. Remem-ber, we’re not talking about whether or not the car starts, runs and stops.” • “Those shops open weekends just have kids or guys who may be able to do a few simple jobs, but no real technicians there to do real repairs.” And similar, “All you’re going to get on a weekend is ‘gas and go’ for air conditioning, and we do real leak detection and repair.” • “We do a lot of general auto repair too. If I open for some types of work, the pressure will be on to do more than oil changes and brake jobs. As it is, we schedule very carefully on Friday so we get everything possible out the door. Usually, nothing

sits over the weekend.”These comments may be true, but we should also note that

many dealer parts depart-ments also are open on Satur-days, and they are selling to more than do-it-yourselfers. We’ll also point out that A/C is a seasonal business, and there’s nothing that says you have to offer full service on weekends – or for that mat-ter – any other individual day of the week. With fl ex-ible hours in such wide use today, you could have a spe-cialist off duty on a weekday. Some technicians may prefer Sunday-Monday off, for ex-ample.

This article is not a clarion call for Saturday A/C service. We see car dealers that are suffi ciently busy, but have limited service bays, so they can justify running two shifts every day, or even a 7/24 op-eration.

We would never suggest that to a small independent

By Paul Weissler, MACS Senior Technical Correspondent May 2011

A TOUGH DECISION YOU SHOULD MAKE RIGHT NOW

Figure 1: Sign at a seven-day opera-tion that, despite the tire company logo, offers a wide range of auto ser-vice and repair. With people working fl ex hours and changes in lifestyle, weekend (even night) service is tak-ing hold in many areas. If you’re un-sure if some weekend service, even if it’s seasonal, is something you need to offer, start visiting these shops during weekends and determine if there’s business worth pursuing.

ALSO INSIDE THIS ISSUE:

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


The auto industry, facing the 35.5 mpg regulatory mandate for 2016 (with important “early credits” available since 2009), is doing all sorts of things to reduce the fuel consumption of air conditioning. The A/C effect on fuel economy previously did not affect window sticker fuel economy numbers, because the fuel economy test cycles (city and highway) didn’t run the ve-hicles with A/C on. Starting with the 2011 model year, all gaso-line/diesel engine cars are run through fi ve driving cycles, one of which includes A/C on and four of which have a lot of idle stops.

Starting next year, we’ll also be seeing a lot of cars with idle stop (a subject whose effect on A/C we’ll cover in a future MACS Service Report). But for now, let’s look at the “ECO” (economy) modes, which are being used on all hybrids in par-ticular, and some conventional models (Figure 2). In fact, some Japanese cars had an air conditioning Economy mode for many

years, a simple A/C module algorithm that with the driver’s push of a button, would change the clutch cycling strategy to increase the cycled-off time. And if you go back to the days of hang-on units, turning the Cool control knob changed the sens-ing by the cycling clutch switch, which (depending on which way it was turned) increased or decreased the cycle-off time, for less or more A/C cooling.

Understanding all these computer strategies – which go be-yond just a fuel economy objective – is important, because they

affect the way an increasing number of A/C systems operate, and that translates into how you troubleshoot a system. You have to be able to tell if A/C performance is poor, or if there’s something else in the picture, and the simple “is the air cold” isn’t so simple anymore. What also enters the picture is the A/C control system in the supposedly normal mode, which also may use an operating strategy that could be confused with er-ratic performance.

In other MACS Service Reports, we’ve talked about the “breeze” airfl ow strategy of some luxury cars (Audi, VW and Infi niti, for example), and that clearly is very different from a max-cold blast of high blower speed air from the center reg-isters. The strategy will have a fuel economy benefi t (even if small), but there’s also a matter of what the engineers believe will deliver a more comfortable level of climate control. After all, 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, any A/C cooling request from the driver is modifi ed accord-ing to what is needed for effective defrost, and if this requires a change in the calculated cooling load, the computer calls for it, and if necessary may increase the compressor displacement. It also can vary the temperature between upper and lower regis-ters, so if the solar load is high, the upper registers deliver cooler air.

There’s a lot more to it, including the fact that the computer also controls the output of the engine’s electric water pump, so the need for engine cooling vs. cabin heat also must be part of the strategy. But basically it means that you can’t just think, “Well, it should produce colder air and the blower should run faster.”

Further, this system (like most other late model ones) has a

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 maximum effi ciency. If you see the “ECO” on the instrument cluster of this Lexus CT200H, HVAC performance will be reduced, perhaps below what the customer expects.

ECO MODES—WHAT THEY ARE AND HOW TO TEST THE SYSTEMS

garage. You and your employees still want to have a life, and if you offer a reasonable package of convenience and fairly-priced good service to your customers, you’ll do fi ne.

But hours of operation depend on the service mix in your shop, and what competition requires. If you feel there could be a marketing advantage to Saturday service and you can work out the fl ex hours with your employees, you could be the one shop or the fi rst shop in your area that forces the issue-- and there’s nothing wrong with that. If dealers are closed on weekends and parts are near-impossible to get, you could decide otherwise, or stick to a limited range of services.

What’s wrong with taking in an A/C job on a Saturday, fi nd-ing out it needs a compressor you can’t get at that time, and

bringing the customer back? The fact that you booked the job on a Saturday is the plus business. However, lots of A/C jobs may be completed with parts in your stockroom, or if there’s a leak you can’t fi nd, add a dose of trace dye and tell the customer to bring the car back on Monday.

The economy is still in the doldrums, and being competitive is important. Located in a business district that clears out for the weekends? That makes the decision easy. However, if you pull from residential districts and want to post Saturday service (per-haps with an early closing) as a seasonal offering featuring air conditioning work, you still are free to change hours of opera-tion in winter. ■


refrigerant capacity of just 16 oz, which means that any sealing failure that causes a loss of just a couple of ounces or more can produce a loss of cooling performance. Also, in part for Federal emissions credits, the systems are changing system refrigerant controls. As you should know, evaporator temperature control today may allow the evaporator core temperature to rise into the mid-40’s (or even higher) if the A/C cooling load is low, vs. the conventional system that always cools the evaporator to “32 degrees F.,” then reheats the air in the plenum to produce the desired comfort level by an air temperature mix. We’re also seeing a continuous use of partial recirculation, so that much

of the cooling is to already cooled interior air, but without the nearly 100% recirculation that would be used with Max Cool. The recirc level is from a complex computer calculation con-tinually adjusted according to what temperature air must come from the A/C registers. The setting is largely from an effi ciency standpoint, within limits that include factors for humidity and temperature levels outside and within the cabin.

Combine that with a system that in ECO mode is designed to reduce A/C cooling below what the motorist called for (mean-ing higher A/C register air temperatures), and you can see the 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 signifi cant some are for the particular situation. These “decisions” create “target” settings that are corrected for a satisfactory overall result, such as enough airfl ow 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 HVAC fl ap doors, are operating properly.


How do I know what’s normal, what is represented by a refrig-eration system problem, or perhaps a drifting sensor or an out-of-calibration fl ap door in the HVAC case?

When you have a system designed to operate within tight parameters all around for maximum effi ciency, the A/C perfor-mance level that you’ll be required to restore must include that “ECO” mode to the extent possible. After all, the buyer of a hy-brid with fuel economy numbers of 40-50-plus mpg is not going to run the car in regular mode and tolerate a fuel economy drop into some unacceptably low number, like maybe 30 mpg (yeah, that would make for one very unhappy owner).

So for openers, it comes down to this: Turn off the ECO mode, by just pressing the button at the bottom of the control

stack (Figure 4). Select LO for temperature with me-dium blower (the system also should be in recirc and airfl ow through upper reg-isters). If you can get the performance you expect in maximum cool Auto and/or an equivalent manual mode, that proves the re-frigeration system works (Figure 5). As for the auto-matic A/C performance in ECO mode, don’t think about installing a new con-trol module unless there is a diagnostic routine that points to it. More likely there’s something else involved if performance is weak, such as sticking fl ap 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 pass-through device that uses the SAE J2534 protocol for scan 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 refl ash 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 Identifi x 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-tion – example: Even the Lexus CT200H normal mode for set temp or ambient temp could be set for plus/minus 2 degrees C (plus/minus 4 degrees F) from the display, if that was preset (double effect possible). Or the blower speed could go up in de-frost, or ECO drive operation could be cancelled when the A/C is turned on (interesting one to keep in mind). ■

Figure 4: To turn off the “ECO” setting, which reduces Climate Control performance for fuel economy, press the knob at the center bottom of the control stack. To restore “ECO,” turn the knob to the left.

Figure 5: The best way to evaluate cooling capacity is to check perfor-mance with the system in a manual mode (including recirc and LO set-ting on the temperature dial) and a medium blower setting. You also can do this in Auto and in addition, in LO setting, which checks some of the automatic control, but without all the neural network adjustments.

Figure 6: Mongoose scan/reprogram tool, based on the SAE J2534 protocol, is available for Toyota/Lexus/Scion and Detroit three makers’ vehicles. It’s $495 and does both factory scan data/ trouble codes, and reprogramming, in conjunction with a PC and a suitable subscription to the premium level of the factory websites. The Toyota one is supported by Toyota, which includes tech support.


When was the last time you replaced a water pump and torqued the bolts to specifi cations – in stages—with a torque wrench you knew was reasonably accurate? We’re not going to take a poll using a lie detector, but we suspect few readers could honestly answer yes to all three parts of that question. And now we’ll add a fourth: in the correct sequence.

Most reputable tool suppliers offer torque wrench calibration service, and they sadly aren’t deluged with business that we’ve heard. Worse, we’ve seen torque wrenches, those big click-off micrometer – set types, tossed into a toolbox after use (well, at least someone had the idea of using it). It’s supposed to be set

back to zero after use, so the preset spring inside can relax, rather than take a set. And if you haven’t used it in a week or so, set it to some reason-able torque (maybe 50-75 foot-pounds on a 0-150 range wrench) and torque a few bolts before you take it to the job.

The beam-type torque wrench is low-cost and unless mishandled, retains accuracy for a long time, but it just isn’t convenient to use. Working on cars means setting torque when you can’t see a dial,

so the click-off is the almost universal choice. However, if your 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 type matches it. That’s not perfect, but at least it isn’t total guess-work.

There are electronic torque wrenches (well, the electron-ics measure a strain gauge) and they hold accuracy better, but aren’t cheap, and even they don’t like a beating. The enclosed split-beam torque wrench is a choice if you have a technician or two who doesn’t treat these tools as well as he should, including the fact that they don’t have to be reset to zero. Although few torque wrenches are accurate at the ends of the scale, the Preci-sion Instruments one is rated for plus/minus 4% from 20-100 foot

pounds. Now let’s look at the

water pump issue. Gen-eral Motors has released a bulletin that says a re-quired torque sequence applies to their “high feature” V-6s (the 2.8, 3.0 and 3.6-liter engines with dual overhead cams and typically variable valve timing). Note the sequence, which is tightening bolts a star-alternate way, some-what similar to road wheels. The spec torque is relatively low, so GM says you can tighten to 12 N-m/106 inch-pounds (9 foot-pounds) and then just repeat that torque, in the same se-quence (Figure 7).

The sequence was instituted to reduce gas-ket leak issues on these all-aluminum engines. Of course, precise torque is meaningful only if the gasket was mounted on a cleaned surface and the bolt holes are all clean and dry.

And Those Intake Manifold BoltsReplacing GM pushrod V-6 intake manifold gaskets is a com-

mon cooling system repair, and here again, proper torquing of the manifold bolts is important for sealing with the new gaskets. The bolts on the 60-degree V-6 engines are not reusable. Those on the 3800 90-degree V-6 are reusable (Figures 8, 9, 10). The sequences, similar to cylinder heads, are center-start and then work alternately to the ends.

In the case of the 60-degree V-6, not only do you have to torque to the specifi c sequence, but like road wheels and cyl-inder heads, in two stages, and to two different torques (one spec for each set of four bolts) to ensure

good sealing (Figure 11). ■

TORQUING WATER PUMP BOLTS

Figure 7: GM’s recommended sequence for tightening water pump bolts on their “high-fea-ture” DOHC V-6 engines (2.8, 3.0 and 3.6 V-6s).

Figure 9: Lower intake manifold gasket torque sequence for 3800 V-6.

Figure 8: “Torque to specifi cations” is important when replacing intake manifold gaskets on GM pushrod V-6 engines, such as this 3800 90-de-gree V-6.

Figure 10: Upper intake manifold gasket torque sequence for 3800 V-6.

Figure 11: Lower intake manifold gasket torque sequence for 60-degree V-6 (3.1 liter shown). At fi rst, all bolts should be torque to 7 Newton-meters (62 inch-pounds). Then bolts 1-2-3-4 should be tightened to 13 N-m (9.5 foot-pounds), and 5-6-7-8 should be tight-ened to 25 N-m (18 foot-pounds). All intake manifold bolts on the 60-degree V-6s should be replaced. The upper intake manifold bolt tight-ening sequence is similar, but all bolts should be tightened to 25 N-m (18 foot-pounds).


THOSE HVAC CASE ACTUATORS

The temperature (blend-air) door actuator on the 1997 Buck LeSabre was clearly not moving, despite the fact that it was a brand-new one that replaced one that verifi -ably had failed. The actuator was a typical General Mo-tors fi ve-wire type, like the type also used by Ford, in which two wires form the fi ve-volt reference signal, two the reversible 12-volt signal to operate the motor and one for the motor position feedback signal (Figure 12). The technician found 12 volts on the No. 10 terminal and varying voltage at No. 8. He looked for a ground at No. 7, but there was nothing. No, it wasn’t a wiring problem, but the wrong actuator, as he realized when he removed it and took a close look inside its connector: no terminal for B7.

The wrong part being a perfect-fi t replacement for the right one is no enormous surprise. But with HVAC case actuators, the situation can work in a number of ways. Here’s an example from a 2000 Honda Accord, where the onboard diagnostics (which can be run through the HVAC control panel) had logged a code for a failure in the temperature door control linkage, motor or door it-self. Okay, the technician fi nds the motor is seized, or-ders a replacement and the new one doesn’t work either. Same basic problem as previous: the wrong part, in this case the recirc door actuator was sent instead of the tem-perature door unit, and the correct part works fi ne. The tipoff: the recirc motor is physically the same, but uses just three of seven terminals, whereas the temperature motor uses fi ve.

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 specifi c terminals of the HVAC control module, they can be operated in a similar manner but controlled specifi cally 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 fi ve-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 fl ap 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 infi nitely variable. The computer goes through pulse counting until it fi nds each fl ap door’s stop at one end, then reverses direction (by changing motor polarity) to fi nd the opposite end. In the case of the recirc door, the computer has to provide only two positions, although we eventually may see the computer provide some intermediate steps for improved tempera-

Figure 12: Five-wire actuator for General Motors HVAC. Although the housing may be different for packaging purposes, the internal arrange-ment is similar for all, a two-wire fi ve-volt reference circuit, a two-wire circuit for the 12-volt actuator motor, and a feedback position wire.


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

ture control by mixing cabin and outside air. The mode door actuator, of course, can be stopped in positions for up to three doors (fl oor, panel and defrost/demist. The single zone systems have just one blend-air actuator; the dual-zone (side-to-side) have separate ones.

Not surprising, the two-wire system works by pull-ing voltage low on one side and high on the other, to cause movement in one direction or another. However, if the voltage is the same along both wires, the motor will stop—that’s the way it’s supposed to happen. If it’s working, but not the way it should for the operating con-

ditions, the problem is not in the actuator motor itself, a point not to forget in the haste to get a job done.

All the operation and positioning is software in the computer, with readings from the sensors. There are no adjustments and no repairs, so if the actuator motor doesn’t work and the connections to the two-wire sys-tem are good, you have to check voltages to the actuator, and then the appropriate sensor inputs, before you just pop for a new part.

Because it’s all software-determined, what you fi rst can do is look for trouble codes, provided of course,


MACS Service Reports is published monthly by the Mobile Air Conditioning Soci-ety Worldwide. It is distributed to members of MACS Worldwide and is intended for the educational use of members of the automotive air conditioning service and repair industry. Suggestions for articles will be considered for publication, however, MACS Worldwide reserves the right to choose and edit all submissions.

Editors: Elvis Hoffpauir, Paul DeGuiseppiProduction Designer: Laina CaseyManager of Service Training: Paul DeGuiseppi

Mobile Air Conditioning Society WorldwideP.O. Box 88, Lansdale, PA 19446

Phone: (215) 631-7020 • Fax: (215) 631-7017Email: [email protected] • Website: www.macsw.org

your scan tool can read these manufacturer-specifi c codes. The factory scan tool has the software, and it’s up to individual aftermarket scan tool companies to add it to their tools’ capabilities. From there, diagnosis comes down to ensuring that if there’s a short or open, you trace the wires, fi nd and fi x. The only signifi cant alterna-tive codes are:

• Failure to move enough, to a specifi c posi-

tion, which could be a binding door, of course.• Moves too far, which could be a door with stripped links or cracks in the linkage or may-be defective stops.

Because door movement problems can cause perfor-mance issues, either of the movement errors also could be a software issue, and you should be checking for an update. ■

Figure 14: Chrysler HVAC actuators are two-wire type, so the control module counts pulses to determine position and reset the fl ap door to a new position as required. Note that in addition to the specifi c 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.

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

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2011 05 Ms