Looking for mobile A/C wiring diagrams? We know where they are!

MACS mobile A/C diagnostics app includes wiring diagrams for mobile A/C systems for cars and light duty trucks. The only way to get the MACS mobile A/C diagnostics app is to become a MACS member. Join Now! Visit the MACS website at www.macsw.org

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Tata Motors and MAHLE partner together to develop a prototype Secondary Loop Mobile Air Conditioning System on a vehicle

Tata Motors Limited and MAHLE, one of the world’s 20 largest suppliers to the automotive industry, have signed a joint development agreement for designing and developing a Secondary Loop Mobile Air Conditioning System (SL–MAC), under the aegis of United Nations Environment. MAHLE and Tata Motors, along with the Institute for Governance and Sustainable Development (IGSD), which is coordinating the project, received funding for developing the SL-MAC system from the Climate and Clean Air Coalition to Reduce Short-Lived Climate Pollutants (CCAC), a global initiative to support fast action and make a difference in the areas of climate, public health, and food and energy security (www.ccacoalition.org). This project envisages use and trial of environment friendly, low global warming potential (GWP) refrigerants HF01234yf (ASHRAE A2L) and HFC-152a (ASHRAE A2).


A team comprising of representatives of the California Air Resources Board (CARB), the Mobile Air Conditioning Society Worldwide (MACS), the National Renewable Energy Lab (NREL), MAHLE, Tata Motors, and IGSD reviewed the newly constructed SL-MAC system and the prototype at the MAHLE Behr facility in Lockport, New York, USA, on 7 April 2017.

A Tata vehicle based on a new generation platform for utility vehicles, consisting of a more complex architecture with front and rear air conditioning system, has been selected for this joint development program. The SL–MAC system will first be installed in the Tata utility vehicle as a prototype. In the SL-MAC system, the alternative refrigerants first cool a secondary fluid/coolant, which in turn cools the air to comfortable temperatures inside the vehicle cabin. This process allows the safe use of slightly flammable refrigerants that have a low GWP and in turn achieves high cooling capacity, minimizing the losses and achieving an optimized overall thermodynamic efficiency in the process. This is in contrast to the conventional mobile AC system, where the cabin air is directly cooled by the refrigerant HFC-134a, which is ozone safe but has a high GWP.


According to Dr. Tim Leverton, Chief Technology Officer, Tata Motors – “Tata Motors has been at the forefront of innovation and is constantly working towards shaping the future of mobility. As a part of our R &D efforts, we are committed to pioneering and inventing solutions to a greener future in the auto industry and this initiative is a step in that direction. We are the first OEM in India who is developing and evaluating an SL-MAC system on a car, using environmentally friendly refrigerants. We are delighted to work with class leading global suppliers like MAHLE and institutions like IGSD to contribute to the United Nations Environment initiative.”


The new SL-MAC system, which is testing the low-GWP refrigerants, is expected to increase vehicle energy efficiency through engineering. This system will turn off the compressor during acceleration and will retain coolness when the compressor is inactive or the engine is turned off for a short duration, allowing rapid cool-down at re-start. In addition to the expected energy efficiency benefits (fuel saving of up to 3%), the SL-MAC system allows the use of refrigerants that should avoid flow into the vehicle cabin. The refrigerant never enters the passenger compartment and instead stays in the engine area. Only the coolant circulates through the interior air conditioning unit.


According to Dr. Stephen O. Andersen, PhD, Director of Research for IGSD – “The Secondary Loop System will permit the use of alternative refrigerants like HFC-152a (GWP of 138) and HFO-1234yf (GWP<1) which have much lower GWPs than the current most-commonly used refrigerant, HFC-134a (GWP of 1300). We will be comparing the life-cycle carbon footprint of HFC-152a – with a higher GWP offset by higher energy efficiency – to the carbon footprint of HFO-1234yf and we will be estimating the cost of manufacture and ownership for each system”.


The SL-MAC project is on schedule, as expected, with anticipated environmental and cost advantages to be determined in the next stages. The prototype will be tested on the Indian roads later in the third quarter of 2017, where long seasons of hot and humid weather and stop-start driving conditions make a secondary loop air conditioning system highly advantageous.

To know more, please visit (www.tatamotors.com; also follow us on Twitter: https://twitter.com/TataMotors

MAHLE is one of the world’s 20 largest suppliers to the automotive industry (www.MAHLE.com).

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Keeping pace with change

We have been hearing about the evolving and expanding roles of air conditioning and cooling as technology continues to develop. A couple examples will appear in the 2018 Dodge Challenger SRT Demon to be released this fall.

When in Drag Mode, the air conditioning system of the Demon is diverted to chill the engine’s charge air cooling system. The vehicle is also equipped with an After-Run Cooler, which continues to cool the car after it has made a pass down the drag strip.

Of course, it’s unlikely that we will see the Demon in our bays. Only 3,000 will be produced.

However, we are seeing new cooling applications. Most are for EVs and plug-in hybrids, some of which have three separate liquid cooling systems. But look under any hood and you’ll discover hose connections galore. You’ll also see more engine and transmission cooling because (definitely for the transmission) there can be a CAFE credit.

The keynote address by Dr. Mark Quarto at our annual meeting this year featured “The New Role of an Air Conditioning System,” and how our future is changing to support hybrid, electric, fuel cell and other advanced technology vehicles.

His message: “The role of the A/C system has dramatically changed as hybrid, plug-in hybrid, battery electric, extended range electric and fuel cell technologies continue to populate the vehicle landscape. No longer strictly a cabin cooling system, the A/C has become a crucial system for cooling high voltage electronics and battery packs. With this new role, the A/C system is now part of a larger, high voltage integrated thermal management system. The result of this integration means diagnostics and repair become more expansive and potentially more profitable for MACS members.”

During his presentation at the MACS 2017 Training Event, Bob Pattengale, the North American Training Leader for Robert Bosch LLC, heightened awareness of how widespread technological change is impacting the industry. “Modern climate control systems today not only employ more and more modules, they are also using an increasing number of actuators and sensors. Besides understanding emerging communication network topologies, technicians need to ensure their diagnostic approach, service procedures and associated skills are in step with technological changes.”

Another presentation by MAHLE’s Timothy Craig and Lindsey Leitzel echoed this theme. “Mobile air conditioning refrigerant systems are rapidly evolving in response to a number of drivers,” noted Craig. “These include the ongoing quest for improved efficiency and lower environmental impact, new vehicle architectures (notably the electrification of powertrains and other vehicle systems), the adoption and mandating of new refrigerants that feature lower Global Warming Potential (GWP), and other forces.”

Craig and Leitzel suggested that the service sector, “Expect, prepare for and then leverage the opportunity presented by increasing complexity in vehicle refrigerant systems and associated hardware. For instance, recognize that service demand will likely be as strong on controls and sensors as it is on parts and refrigerant.

“Expect the growing complexity of mobile air conditioning and refrigerant systems management to impact the industry with more parts, more sensors, more functions and systems, and clearly, more service needs. Look and prepare for them. And remember, it’s important to review the basics to understand the incoming change evolution. Knowledge and comprehension will improve your opportunity and maintain your ability to resolve customer problems.”

Looks like we have our work cut out for us!

Not a member of MACS yet? What are you waiting for? Join now! Visit the MACS website.

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

Get the MACS mobile A/C diagnostics app with your paid MACS membership


Nearly a year in the making, the MACS mobile A/C diagnostics app is now available. The MACS board of directors decided last fall that it was time for MACS to fully embrace current technology and push our information out to mobile devices for the benefit of all of our members. The app was created by MACS member and digital industry leader SHIFTMobility.

All MACS members will receive the MACS mobile A/C diagnostics app provided their membership renewals are paid.


The app is for both Apple and Android mobile devices and can be downloaded from your respective app store (MACS Mobile A/C Diagnostics). After the download, expect to be verified within 24 hours.

How does it work?

The MACS mobile A/C diagnostic app is a native app, meaning you have the ability to use many of the built-in features of your mobile device.


On the top of the screen, to the right of Mobile A/C Diagnostics, you will see a stacked bar icon.

Press it to access settings.

This is where you can change your password and add your business information.

Mobile A/C system specifications

The icons directly below the title, Mobile A/C Diagnostics, are used to identify/select the specific vehicle information you are looking for. For example: refrigerant charge.

  • Vin: Press the Scan Vin icon, type in the VIN and confirm.
  • Plate: Press Plate and enter the letters and numbers for the license plate along with
    the state.
  • Vehicle: Press Vehicle, select year, make, model, sub-model (if applicable), engine.

After completing the vehicle selection all available information is ready for selection. Simply touch what you are looking for.  Hint: Because this is a native app, all images are expandable by placing two fingers on the screen and spreading them apart.

Truck and off-road vehicle data

To access all available truck and off- road vehicle data simply touch the area where the title, Truck and Off Road Vehicle Data appears. You will be taken to the truck and off-road vehicle data library.  You can either browse for the data you are looking for or enter a key word to be presented with the available information. MACS members ATC, AGCO and T/CCI Manufacturing have provided pdfs of helpful reference data. Keep in mind that truck reference data is VERY HARD TO OBTAIN and MACS has exhausted all resources to acquire it. Our best resource was our member suppliers and we are grateful for what they have shared with us.

The best of all MACS resources have also been added to this app so you can have them in the palm of your hand for access.

MACS Service Reports

To access the MACS Service Reports archive, simply touch the area titled Service Reports.

Press the year and then the month. This allows you to view the entire issue of MACS Service Reports for that month and year.


To access past issues of ACTION Magazine, simply touch the area titled ACTION Magazine and select the issue you are interested in viewing. This allows you to view the entire issue.

Training Resources

To access training available from MACS simply touch the area titled Training Resources.  You will be taken to the MACS website where you can view all of the available resources.

Mobile A/C Service Checklists

To access the service checklists simply touch the area titled Mobile A/C Service Checklists.  You will be taken to a screen with multiple thumbnails.  Simply touch the thumbnail that interests you and it will become visible.  In the upper right corner, you will notice three stacked dots.  Touch the icon to be able to “Send,” “Open With,” “Download,” “Print” and “Report a Problem.” To print directly from the app, you must follow the steps to configure your printer.

Supplier Directory

To access the MACS Supplier Directory, simply touch the area titled Supplier Directory.  There you will find a list of MACS member suppliers along with a hyperlink which will take you directly to their website or a phone number if there is no website. Just touch the company you are interested in and off you go.

As always with all MACS member services, if you have any questions call the MACS office at 215-631-7020 x 0 or email membership@macsw.org.

Once again you must be a paid member of MACS to access our app. Join us now!





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HD and OTR vehicle service: Keep it clean

July/August 2017 MACS ACTION Magazine

It’s been said that cleanliness is next to godliness. This can also be considered gospel when servicing heavy duty (HD) and over-the-road (OTR) refrigeration. These systems operate in far more severe conditions compared to those installed in the lowly light-duty vehicle. All systems must be kept clean both inside and outside, which is a tall order for HD and OTR.

Take a moment to consider the annual cycle of an OTR system. It can sit for months in sub-zero weather and may be placed into 24-7 service when seasons change. Consider what happens to the system during its down time. While not operating, could the refrigerant leak out over time? If not leaking, could undesirables enter the system while idle?
Read the rest of this article  

Download the July/August 2017 MACS ACTION 

Join MACS Today

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Cool runnings

By Steve Schaeber, MACS Technical Editor

The main purpose of a thermostat is to help the cooling system regulate engine operating temperatures to within the manufacturer’s specification. This is normally done by first remaining closed to allow engine coolant to warm up, and then gradually open all the way as temperatures near spec. But sometimes this doesn’t happen, as in the case of a fully or partially stuck open thermostat.

When a thermostat sticks open, engine coolant is allowed to circulate without much restriction throughout the cooling system. This sounds great, and it’s important for this to happen after the proper operating temperature is reached.  However, if it happens too soon the engine coolant may not be able to reach a high enough temperature. This problem occurs because modern cooling systems are actually quite efficient, and are able to transfer a lot of heat from a lot of liquid in a relatively short period of time. When the coolant is not allowed to warm up fully, it basically circulates from the engine to the radiator and back to the engine, losing so much heat with each pass that it stays relatively cool.

Problems attributed to a cold running engine include lower HVAC heater output, engine performance issues and increased tailpipe emissions. But it also prevents the evaporation of condensation that forms on the inside of the engine block. If this water doesn’t burn off it can oxidize the metal (producing rust) and cause an oil sludge buildup in the bottom of the pan.

Engine oil is also affected by the thermostat, and it’s important for it to reach an operating temperature of approximately 190°F. Oil that is cold is not quite as viscous as the substance when it’s warm. Transmission oil coolers are also affected because they are generally in direct contact with engine coolant.

An easy way to determine if a thermostat may be stuck open is to simply monitor coolant temperature. Some vehicles have a dashboard temperature gauge, but many technicians prefer to use a scan tool with graphing capabilities. Begin when the engine is cold and connect your scan tool before starting the engine. Graphing the coolant temperature sensor PID will allow you to watch the thermostat to see what happens over time. If the thermostat is only partially stuck open, you may notice a rise in value to a relatively warm number, perhaps around 150°F. But if it’s stuck open all the way, temperatures may not increase much past 120°F.

Many PCMs will also monitor thermostat operation, illuminate the check engine light and produce a trouble code if there’s a problem. Ford uses P0125, Insufficient Coolant Temperature for Closed Loop Fuel Control, along with P0128 Coolant Thermostat (Temperature Below Thermostat Regulating Temperature). Issues could be related to slow warm up times, low coolant level, or sensor output issues, as well. Sensor readings may be double checked by using a mechanical thermometer or a thermocouple connected to a digital meter.

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Thermocycle leaks

Radiator leaks are nothing new, and some technicians may initially blame a faulty part, poor construction or shoddy workmanship during installation when a leaker shows up in their bay, particularly when it’s a later model vehicle that has failed. But sometimes the radiator may be the victim of rapid coolant temperature changes caused by a faulty or rapidly degrading thermostat that is opening and closing too often.

When this happens, hot, then cold, then hot, then cold, then hot, then cold (you get the idea) coolant is sent from the engine block to the radiator, effectively shocking it back and forth from hot to cold and then back again, over and over. This rapid change is called thermocycling, and it causes radiator tubes to quickly expand and contract so much that they disconnect from the radiator’s side tanks, allowing coolant to leak out. It’s a failure similar to those found in the solder joints of copper pipes or on electronic circuit boards.

GM has identified similar issues in vehicles including certain 2014-2015 Chevrolet Silverado, Suburban, and Tahoe models, as well as the GMC Sierra, Yukon and Denali, and the Cadillac Escalade with 4.3, 5.3, or 6.2L engine. In a series of Technical Service Bulletins, which include #PI1513B titled, “Coolant Smell and/or Slight Leak at Radiator,” issued on November 30, 2016, GM presents comments made by customers, such as smelling coolant while driving or when outside the truck. These complaints may or may not include a coolant leak under the front of the vehicle.

GM recommends that technicians begin their diagnostics by inspecting the radiator for any signs of leaks, such as those that may exist where the flat radiator tubes meet the side header tanks. Particular attention should be paid to the four corners of the radiator, areas which may experience the most fluctuations. The cause could be related to excessive thermocycling of the cooling system,  brought on by excessive cycling of the thermostat.


Technicians’ initial conclusions are often an incorrectly constructed radiator , or a weak tube to header joint, which allows coolant to leak. In some cases, the technician may successfully replace the leaky radiator only to have the replacement fail after a period of time, ultimately causing the owner to bring the car back to the shop, The technician could assume the replacement radiator is also defective and  exchange it once more. But the actual root cause of the fault may be the thermostat, which if it cycles open and closed too often, can shock the radiator by sending out cool and hot coolant. Ideally the temperature of the cooling system should remain constant, or change slowly over time without rapid, frequent or excessively wide changes in temperature.

The final fix includes not only a thorough inspection and replacement of the radiator to solve the leak problem, but also changing out the thermostat, and of course, GM has an updated part number to address the overcycling.

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MACS mobile A/C diagnostics app is now available for download for MACS members

In response to MACS member needs and changing technology MACS has partnered with Shiftmobility to create the MACS mobile A/C diagnostics app for use on mobile devices. The app will include access to the MACS Service Reports and ACTION Magazine archives, checklists to aid system diagnosis, access to MACS member manufacturers and distributor suppliers and an extensive mobile A/C vehicle specifications library.

Vehicle reference specs will include:

A/C & Heater Service, A/C System Specifications, Component Location Diagrams – HVAC Systems Only, Cooling System Bleed, Diagnostic Trouble Codes – HVAC Systems Only, Miscellaneous Capacities – HVAC Systems Only, Radiator & Hose Replacement Procedures and Wiring Diagrams – HVAC Systems Only.

Only MACS members in good standing will have access to this APP. To access the MACS Mobile A/C Diagnostics app visit the Google play store for android devices or the iTunes store for Apple devices. One free download is included with MACS membership. Additional downloads are $60 each. For a larger overview and users guide click here.

After you choose the app, MACS will verify your membership and approve your use.

For more information email marion@macsw.org or call 215-631-7020 x 304.

Not a MACS member? Join here. 

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Today’s technicians need to be total climate control management forensic scientists  


MACS June ACTION Magazine is all about mobile A/C diagnostics!

By Peter Orlando, MACS Contributor

 Technicians need proper skills to work on today’s climate control systems. It is up to industry professionals to ensure they are service-ready and have all the necessary certifications and safety awareness training before they attempt any A/C service work on a vehicle.

We are required to perform a diagnostic system performance test to determine what diagnostic direction we will take on the problem based on the customer’s complaint. Many times, we need to determine up front if a problem is addressed by a Preliminary Inspection or TSB. If we don’t, we can waste many hours on a problem. Following proper OEM test procedures is essential for achieving a job well done, delivered on time and at the price agreed upon while making a profit. Read the rest of the story here.

Download the entire June 2017 MACS ACTION Magazine

Posted in #1234yf, ACtion Magazine, MACS Member, Mobile Air Conditioning, Refrigerants | Tagged , , , , , , , | Leave a comment

MACS Summer of Service Videos

Calling all MACS members! MACS is launching the summer of service videos!

Send us a short mobile A/C technical tip video less than 10 minutes that explains a service procedure or is educational and not overly commerical and we will post it on our website homepage for one week this summer.

You must send us an embed link and again not overly commercial it is fine to mention a product but we are looking for solid tech tips.

This is a great opportunity for MACS member companies to get more traffic for their service videos and help educate the industry.

Email your video embed link to marion@macsw.org.

MACS reserves the right to refuse any video we deem not to be appropriate.

You must be a member of MACS to participate.

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