School bus A/C

By Steve Schaeber, MACS Technical Editor

I recently had the chance to tour Rifled Air Conditioning in High Point, North Carolina, where they install new A/C systems into school buses. It’s fascinating to watch the teams work together, as they install these unique A/C systems.

DSC_7083 Fig 1Air conditioned school buses can be found throughout North America. Usually it’s only mandated for special needs buses, but with high temperatures and humidity during much of the school year, many buses in southern states have A/C.

DSC_6875 fig 2Depending on their size, buses can have multiple, independent A/C systems installed side by side. This bus has three systems: A front or dash system provided by the vehicle manufacturer, along with two additional systems installed by Rifled Air Conditioning.

DSC_6877 fig 3Bus A/C systems are typically referred to by their installed location: front, mid and rear. This mid unit hangs from the ceiling, while the rear unit is integrated with the rear bulkhead.

DSC_6964 fig 4

Installation teams work together to install A/C systems at Rifled Air Conditioning

DSC_7054 fig 5Even though they’re really big, there’s only so much room for heat exchangers at the front of a school bus. Many times the mid and rear A/C system condensers are mounted along the side and are referred to as Skirt Condensers.

DSC_7068 fig 6Just as with any other A/C system, performance is highly dependent on having a properly charged system. On this school bus, the A/C charge label can be found on the inside of the electrical panel, along with A/C system relays, fuses and connectors.

Are you interested in learning more about these complex and highly important A/C systems? Make your plans now to attend the 2016 MACS Training Event and Trade Show! Several classes will cover bus A/C, HD truck and specialty vehicle A/C. Visit for more information, or call us at (215) 631-7020 to register. We hope to see you in Orlando!

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Download the MACS 2016 Training Event and Trade Show Program

MACS Training Event Registration opens September 1, 2015

2016 Training Event email banner

Download the 2016 Training Event and Trade Show Program

The MACS Annual Training Event and Trade Show will take place February 11 to 13, 2016 at the Caribe Royale All Suite Hotel and Convention Center in Orlando, Florida. The 2016 program theme is Mobile A/C: The Next Generation!


“The MACS convention theme recognizes the automotive service industry is in the midst of the largest generational shift in its 100+ year history. The men and women who will be stepping into those leadership roles face technology and business challenges we could only scarcely imagine 25 years ago. MACS is fortunate to have many under-40 members and participants and this event will celebrate their role in our changing industry and discuss the proliferation of new technology all of our members will need to embrace,” explained Elvis L. Hoffpauir, MACS president and chief operating officer.

Industry networking is the number one reason attendees cite for attending, as the MACS annual Training Event and Trade Show is the number one meeting place for all professionals in the total global vehicle climate and thermal management industry.

MACS will have a blockbuster line-up of mobile A/C technical training covering automotive and light duty truck, heavy duty truck, off-road and recreational vehicles. Industry experts from ACDelco, American Cooling Technology, Bergstrom, Caterpillar, DENSO, Eaton, Fiat Chrysler, Ford, Four Seasons, Gates, General Motors, Jaguar, Red Dot, Robert Bosch, U.S. E.P.A. and many other industry experts will provide information and training.

The MACS Caribe Royale hotel room rate will be $159 single or double plus tax per night. Room reservations can be made online or by calling (800) 823-8300.

Posted in Automotive Aftermarket, Automotive training, MACS Training Event, Mobile Air Conditioning | Tagged , , , , , , | Leave a comment

You don’t see that everyday!

While taking in the sights around Denver, Colorado last week we decided to drive up Mt. Evans for the thrill of being at 14,000 feet above sea level. There is also something wondrous about switchback roads at high elevation with no guard rails. Falling off the mountain would be easy to do if you’re not careful.
As we stopped to take pictures and enjoy the beautiful views we kept seeing three mysterious cars. One was identifiable the other two had squiggly swirls on them.

Curiosity of course got the better of us and at the summit we caught up with the caravan. These were three BMW hybrid test cars outfitted with sensors and computers measuring all sorts of parameters.

Very cool.


Posted in ACtion Magazine, Automotive, Automotive Aftermarket, Automotive training, Hybrid, MACS Member | Tagged , , , , , , , | Leave a comment

The great debate

By Elvis L. Hoffpauir, MACS president and COO

Chances are, if you take any kind of extended road trip over the hot summer months, you’re going to see this sight: two feet sticking out of the passenger side window, legs crossed at the ankle, as a vehicle cruises down the Interstate. Perhaps it’s an expression of freedom or rebellion, a penchant for the sensation of bugs striking flesh at 65 mph or so, or one person’s vote in the years-old debate of which yields better mileage – windows down, A/C off or windows up, A/C on.

Back in 1979 when I first became involved in the mobile A/C industry, I was working for IMACA (the International Mobile Air Conditioning Association), which had just mounted a PR campaign to convince motorists that the use of mobile air conditioning was not only beneficial, but more fuel efficient than blasting down the highway with the windows rolled down. That year, the debate was perhaps more important than most years, because it marked the second oil crisis in the wake of the Iranian Revolution (the first crisis occurred in 1973). High prices and long lines at the pump sharpened the focus on fuel efficiency.

Over the years, many have weighed in on the question, including the folks at Discovery Channel’s MythBusters, who tackled the issue twice, coming to opposite conclusions each time. This isn’t necessarily surprising, because a host of variables come into play in any such comparison – variables not easily controlled.


As MACS technical consultant Ward Atkinson observes, “The energy required to provide comfort in a vehicle depends on many factors. The load on the A/C system is a function of the fan setting, the weather conditions, outside temperature and humidity, and the speed of the vehicle among other variables.”


Atkinson further notes, “Since the user has many options in operating the A/C system, it is important to have an understanding of the effect of various settings on fuel consumption. The use of recirculated air and reduced fan speed result in the lowest energy requirements. However, the use of outside air and a selected fan speed will provide a more desirable air exchange and air quality within the passenger cabin.”

Given that many motorists’ knowledge of their A/C systems may not extend beyond turning the systems on or off, a brief tutorial for your customers may be worth your (and their) time. 


AC and Mileage

Much information available in print or on the Internet tells only part of the story. For more detail on this subject (including suggested A/C settings for energy efficiency for various driving and weather conditions), check out the paper by Ward Atkinson and Bill Hill on “Mobile A/C system energy requirements.”


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Military origins of popular civilian rides

By Keith Leonard, Esq.

“Necessity is the mother of invention” is an idiom at least dating back to Plato in his seminal work, Republic, and meaning necessity gives rise to inventors coming up with new and useful ideas and inventions to solve a problem. Similarly, there are often rapid advancements in medical techniques and various areas of technology during and due to a war. Motor vehicles are certainly not exempt from these advancements.

Perhaps the most famous American vehicle that has a military origin to it came out of the United States Department of War’s need, on the eve of World War II, for a light, cross-country reconnaissance vehicle. The compact utility vehicle that was developed was known as the Willys-Overland Model MB. Due in part to the fact that the Willys-Overland Motors company could not produce enough of them for the army’s needs during the war, Ford Motor Company also produced a significant number of this vehicle under the designation of Model GPW. In either case, the army identified the vehicle as “Truck, 1/4 ton, 4×4”. This vehicle was so popular for war-time use that over 50,000 of them were exported to the Soviet Union to assist it in its struggles against Nazi Germany. After the war, the Soviet Union began producing its own variation of this vehicle which it designated the GAZ-46. However, I suspect that most every reader of this article will know the vehicle by the name it eventually acquired with the public – the jeep. A classic early example of the jeep’s “off-road” prowess was a demonstration in early 1941 when a jeep was driven up the steps of the United States Capitol. Advertising of the various Jeep models produced since World War II have emphasized the vehicle’s off-road capabilities. Today, the Jeep brand is produced by a division of FCA US LLC, a wholly owned subsidiary of Fiat Chrysler Automobiles.

DSC_0119Over the last forty years, the United States Army has sought other vehicles to handle similar off-road needs of the military. In the late 1970s, the High Mobility Multi-purpose Wheeled Vehicle (HMMWV) was developed to address the army’s needs for a tactical vehicle. AM General was awarded a contract for such a vehicle, which it began producing in 1984. Some 100,000 HMMWVs had been built by the spring of 1995 in at least fifteen different configurations including troop and cargo carriers as well as weapons carriers and ambulances. In 1992, AM General began marketing a non-military version of this vehicle, popularly coined the Hummer H1. While the World War II Jeep’s ground clearance was 8.25 inches, the HMMWV’s ground clearance is 16 inches, making it a superior off-road vehicle and one which is difficult to roll over.

Not surprisingly, the US is not the only country which has had vehicles originally conceived or developed for military use which were converted to civilian use. Though technically not built for military purposes, an automotive company was founded on May 28, 1937. The company was state-owned in Germany (then under the control of Adolf Hitler) and was first known as Gesellschaft zur Vorbereitung des Deutschen Volkswagens mbH but renamed that same year to Volkswagenwerk, or “The People’s Car Company.” Their cars were initially designed by Austrian automotive engineer Ferdinand Porsche, with the goal being a mass produced and affordable, but speedy car for working-class Germans. Though production of the car was halted during World War II (the factory was converted to military related production), it was again produced after World War II. The car was not a big seller in America until (in 1959) it was dubbed the “Beetle” by an advertising agency, a campaign so successful it became the most popular import car in the US for the next several years.

A well-known military to civilian translation of a vehicle in England is the Land Rover. This vehicle was originally designed and produced in 1948 to outdo the jeep. However, like the jeep it’s been marketed as able to overcome rugged terrain.

Despite environmental concerns, off-roading, whether done in a race or for fun, remains popular throughout the world. And with no shortage of conflicts worldwide, there is also a military need for vehicles that can likewise perform different purposes well off-road.

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Spray bottle test

By Steve Schaeber, MACS Technical Editor

Replacing the accessory drive belt is one of those things that usually falls under the periodic maintenance category, and is something that technicians learn how to do when they first start working on vehicles. These belts are also commonly replaced due to noise issues, which are often difficult to diagnose.

This noise is something we’ve all heard before; that squeak-y, squeak-y, squeak-y sound coming from the drive belt while the engine is running. Sometimes it may go away after driving for a few minutes, but sometimes it will not stop, eventually annoying the driver enough to do something about it. All too often, technicians will replace the belt, thinking it’s worn out and no longer able to grip against the pulleys. This may temporarily solve the problem, but it’s likely to return if the root cause is not addressed.

Belt noises are not usually caused by problems with the belt itself, but rather are attributable to either alignment or tension issues in the Accessory Belt Drive System (ABDS). Knowing what particular type of noise it is can help pinpoint the cause.

Belt noises are not usually caused by problems with the belt itself…

Belt noises are not usually caused by problems with the belt itself…

A chirping noise usually indicates misalignment between pulleys and idlers. Possibilities can be item wear, pulley damage or improper component mounting.

If a belt is squealing however, it’s usually due to a loss of tension in the system, caused by a worn out belt, a failing tensioner, or both. To return the system to “like new” condition, both the belt and tensioner must be replaced together.

Check out the GatesAutoTraining channel on YouTube for a video called Gates Spray Bottle Test. It’s a neat, simple way to help pinpoint the cause of belt noise. More detail is in the video, but here’s basically how it works:

  • If spraying the belt with water makes the noise get louder, it’s usually due to a tension problem indicating both the belt and tensioner should be replaced.
  • If the noise goes away temporarily and then comes back, this indicates one or more pulleys are misaligned.

Note: While you’re on YouTube, be sure to check out the MACSWorldwide channel. Send an e-mail to and let me know which video is your favorite!

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Ford’s MagicAire System

By Steve Schaeber, MACS Technical Editor

In preparation for the September issue, the staff at ACTION™ checks out many classic cars. We’d really like to find some of the earliest examples of factory or aftermarket air conditioning, but are always happy to find some unique or custom HVAC setup, or something we haven’t seen for a while.

Along the road on this quest, we met up with John Posen, owner of this 1957 Ford Thunderbird.

The Thunderbird was one of Ford’s most popular models for 1957

The Thunderbird was one of Ford’s most popular models for 1957

This car doesn’t have an air conditioning system, but it does have an early example of another feature which eventually became standard on almost every vehicle worldwide. Ford called this their MagicAire System, which included a feature known as Recirculated Air Heat.

The idea was to keep out odor contaminated air and fumes from heavy traffic or other outside sources. On the system control panel, the lower knob has to be moved all the way to the left (OFF), while the top knob can be placed at the desired temperature. These settings close off the outside air doors, allowing air in the vehicle to recirculate through the heater.

As long as the bottom knob is set to OFF, the MagicAire System will operate in recirculation mode

As long as the bottom knob is set to OFF, the MagicAire System will operate in recirculation mode

Of course, there’s still a little bit more to it than that. Almost every vehicle back then also had some sort of direct venting. It works as ram air, forcing ventilation while driving at speed. This model Thunderbird has two cowl side vents, one on each side of the car just forward of the doors. In order for the MagicAire System’s recirculation to work properly, these vents must be closed.

The cowl side vent is the rectangular shape, seen just forward of the door

The cowl side vent is the rectangular shape, seen just forward of the door

The cowl side vent controls are located under each side of the dash and are part of the cowl vent assembly. It’s a simple open/closed control. The more you open the vent, the more air you allow to enter the vehicle.

The passenger’s side interior cowl vent

The passenger’s side interior cowl vent

The driver’s side exterior cowl vent. A simple mesh screen prevents debris from entering the vehicle

The driver’s side exterior cowl vent. A simple mesh screen prevents debris from entering the vehicle

Keep an eye out for the next edition of MACS ACTION™ Magazine. September is our classic car issue, featuring some interesting vehicles you won’t want to miss! Visit to learn more!

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The ratings game

This editorial submission has been provided by MACS member Bergstrom

The British Thermal Unit (BTU) ratings for mobile air conditioning systems are a confusing and often misleading issue. Ratings in the marketplace currently range from a few thousand BTU per hour to as high as 18,000 and even 30,000 BTU per hour.

These discrepancies arise because there is no governing body that sets and enforces an industry standard for the testing and rating of cooling and heating capacities. As a result, some manufacturers manipulate and inflate BTU per hour numbers to entice buyers. Bergstrom has developed this article to help trucking executives create an even playing field and make intelligent decisions when comparing mobile air conditioning systems.

Existing Standards & Recommended Practices

With the lack of an enforced industry standard, many manufacturers develop internal standards that are derived from a combination of ratings recommendations issued by industry organizations. These include:

TableIf a company tells you they have a 30,000 BTU per hour evaporator, be sure to ask them how it is rated. Don’t be shy about asking the ratings questions, and if in doubt, ask for clarification or comparison. If they can’t tell you, chances are they have manipulated the numbers in one of the methods listed below.

Increasing air inlet temperature

A higher air inlet temperature will result in higher capacity and ratings. For example, at 100 ºF or above, the higher temperature difference between the air and the refrigerant causes more heat to flow out of the evaporator. As a result, this is one of the variables that can be manipulated to indicate higher capacities or BTU per hour.

Manipulating refrigerant temperature

One method of “increasing” performance is to operate a system with an excessively low refrigerant temperature. However, remember that an air conditioner has an absolute low end for cooling. Do not accept a rating with evaporator air outlet temperatures below 32ºF, because at that condition the moisture removed from the air will freeze in the coil and block the airflow. With no airflow, no heat is added to the passing refrigerant and it will not evaporate. Liquid refrigerant returning to the compressor could cause damage or failure.

Using blower manufacturer’s airflow stats to measure capacity

Another rating deception, often used by companies who don’t own their own test facilities, is to use the blower manufacturer’s stated airflow at a zero-restriction condition. These companies then use that airflow in a coil sizing computer program to publish results. This coil capacity data is obtained from wind tunnel testing of a coil – by itself – with a uniform airflow across its face. In reality, airflow from a blower assembly is delivered with anything but a uniform velocity. Furthermore, using the blower manufacturer’s stated performance at zero restriction is very misleading. The coil itself, along with other system restrictions (such as filters, inlet ducts, outlet ducts and cab pressure), reduces the blower assembly’s output to a lower CFM value.

Rating performance at maximum air temperature and humidity

Many people would like to rate evaporators at 110 ºF and 100% humidity. In theory, this would provide an impressive capacity. However, these people fail to take into consideration that the other components that make up a mobile air conditioning system cannot support those values. To do so would mean that the compressor must pump enough refrigerant, the condenser must remove enough heat and the blower assembly must provide enough airflow across the evaporator to introduce that much load. None of these 3 components can do this.

Neglecting to show time unit of measure

A new trick in manipulating BTU per hour performance numbers is to fail to show a time unit for measure. Most performance numbers are measured in BTU per hour. If no unit is displayed, make sure you follow up with the manufacturer to determine what unit of time they are using to measure BTU per hour.

Bergstrom’s ratings system

With the lack of a governing body that enforces an industry standard for BTU per hour testing and rating, Bergstrom has developed an internal standard that is derived from the ARI 310/380, TMC RP-432 and IMACA 200 recommended practices.

All NITE systems are tested at 80ºF/50% humidity indoor, and 100ºF outdoor. As our capacity has increased, we have also begun to test at 90ºF/50% humidity indoor and 100ºF outdoor in order to illustrate capacity during a pull down situation. While this rating condition shows elevated capacity it is a situation that rarely occurs. Also, Bergstrom only rates its NITE systems based on actual calorimeter test data from our test and development lab. We do not develop any BTU per hour ratings based on theoretical calculations.

We prefer to simulate the downstream restrictions and to mimic the as-installed conditions of the system to ensure proper design requirements are met. Coils, blowers and housings used in testing are the same as those used in real life conditions. We believe this is as close to the actual performance you can get.

To learn more about BTU per hour ratings, don’t hesitate to contact the Bergstrom team at 1.866.204.8570 or

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MACS ACTION magazine honored with five IAMC awards

MACS ACTION magazine has been honored with five medals for editorial excellence by the International Automotive Media Competition. The IAMC program recognizes and encourages excellence in all forms of automotive media from works published, aired, or broadcast in 2014.


The MACS ACTION magazine works honored include; a bronze medal for the column, A rare find in the woods, by MACS manager of service training, Steve Schaeber in the January/February 2014 issue.  A silver medal for the column, Raising the bar, by MACS chairman and CEO, Andy Fiffick from the March 2014 issue. ACTION columnist Keith Leonard, Esq. was honored with a gold medal for his April 2014 column, Classic cars.  A silver medal was presented for his column, Unlock the mystery, to MACS president and COO, Elvis L. Hoffpauir. ACTION contributor and  automotive trainer Becky Witt owner of George Witt Service in Lincoln, NE was honored with a silver medal for her feature, Selling the right things from the May 2014 issue of ACTION.

These awards were announced Sunday, July 26, 2015 during a morning ceremony at the Concours d’Elegance of America at St. John’s in Plymouth, MI.

“We are very pleased to have MACS ACTION magazine recognized by the judges of IAMC. All of our writers and contributors put in a lot of time to provide our readers with the best content possible in our efforts to chronicle the total vehicle climate and thermal management industry,” remarked Elvis L. Hoffpauir, MACS president and chief operating officer.

MACS publications have been honored 78 times since 2001 for editorial excellence.

Since 1981, the Mobile Air Conditioning Society (MACS) Worldwide has been the advocate for service and repair owners, distributors, manufacturers and educators making their living in the total vehicle climate and thermal management industry. MACS Worldwide empowers members to grow their businesses and delivers tangible member benefits through industry advocacy with government regulators and by providing accurate, unbiased training information, training products, training curriculum and money-saving affinity member services. MACS has assisted more than 1 million technicians to comply with the 1990 Clean Air Act requirements for certification in refrigerant recovery and recycling to protect the environment. To learn more about MACS Worldwide visit our website at MACS 2016 Training Event and Trade Show, Mobile A/C: The Next Generation will take place February 11-13 at the Caribe Royale All Suite Hotel and Convention Center in Orlando, FL.

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He wrote the book…

Paul Weissler’s name is ubiquitous within MACS. He’s our senior technical correspondent and has been for the 35 years the Society has existed. His byline appears in literally hundreds of issues of MACS Service Reports, in the pages of ACTION™, and he’s helped host a number of tech forums at MACS’ annual training events.

I know his creds also extend well beyond MACS, encompassing major titles and players within the industry such as MOTOR and SAE International, as well as consumer-oriented pubs you might pick up at your local Barnes & Noble.


Some of Paul’s other titles include: What to Do When Your Car Won’t Run, How to Buy Services and Parts for Your Car, Women’s Guide to Fixing the Car and Auto Repairs You Can Make. 

Still, I couldn’t help being a little impressed when our tech editor, Steve Schaeber, dropped one of Paul’s first published books on my desk. It was Small Gas Engines: How to Repair and Maintain Them published in 1975 by the Book Division of Times Mirror Magazines, Inc.

That got me interested in exploring further. A few searches at turned up a whole list of Paul Weissler titles, probably at least 10 before I stopped looking (even Paul had forgotten some when I later asked him about them).

However, he did recall writing Automotive Air Conditioning, published in 1981 by Reston Publishing Company, Inc. “It may have been the first time R-134a was mentioned in a book,” Paul noted. In fact, he did write about R-134a 15 years before that refrigerant became the accepted industry norm.

Of course, R-134a wasn’t a sure thing when Paul wrote about it in the late ‘70s, early ‘80s, witness this excerpt from the book: “Also under development is a refrigerant, R-134a that does not contain the ingredient in Refrigerant 12 that is considered possibly harmful to the atmosphere. At present, however, Refrigerant 134a is not a suitable carrier for refrigerant oils, so it may pose compressor lubrication problems. Also, although it has been made in the laboratory, there is no presently known way to mass produce it economically.”

Incredible changes have reshaped the industry since Paul first began writing about it. But arguably, no one has tracked those changes more carefully, nor chronicled them more effectively for service technicians, as has Paul.

So if you ever consider calling him out on some technical point, just remember – he wrote the book (several books, in fact).

Posted in Automotive, Automotive training, MACS Member | Tagged , , | 1 Comment