It’s kind of weird penning an article that covers what I learned and experienced at the 2014 Mobile Air Conditioning Society’s training event and trade show in January in New Orleans, when the cold, stiff hands of Old Man Winter still have an icy grip on most of the country. But hopefully, by the time this feature appears in your hands, spring will be well underway and the blustery conditions suffered by many will be fading into the fog of unpleasant memories.
Training Focus On Day Two
After a hard day learning, where better to unwind than on New Orleans’ historic Bourbon Street?
Wait a minute, what happened to day one? In this unique event, day one is a day that is reserved for fun at the MACS event, with golf, bowling or if you’re like me, familiarizing yourself with the scheduled classes and meetings.
So, the real action begins on day two, and that’s where my story starts. In the past, it was my practice to peek in on several classes to gain an overview of what was being taught, but this year I wanted to be a student as much as a reporter and decided to choose among the variety of classes offered and sit through the entire session. That first morning of training found me sitting in on a class on “New Perspectives On A/C Repair,” taught by Richard Sheffield. Being the “geek” that I am, I was intrigued about some of the techniques the course description said he would be sharing as part of his presentation. I never heard of using a Digital Storage Oscilloscope (DSO) and pressure transducers being used for a/c testing before.
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A city view not unlike a dozen others I’ve visited over the last few years. Time to get out and take a look around.
Sheffield’s class began by focusing on common mistakes many techs across the country still make when servicing more modern A/C systems. Many of these tips you’ve read about in the pages of our magazine, and the consequences of not being up-to-date with current servicing procedures include repeat compressor failures, systems that won’t cool as they should and irate customers.
“‘But I’ve always done it this way’ is a typical response offered by these technicians,” Sheffield told the class, asking us if we were one of “those guys.”
One common mistake worthy of discussing here is equipment maintenance. Having worked in a number of different shops over the years, I can testify to the fact that recovery/recycling/recharging (RRR) machines are woefully ill-maintained. Filter reminders are reset (rather than replacing the filter), and vacuum pump oil rarely is changed. And even though current SAE standards governing the capabilities of RRR machines has been in place for several years now, I’m willing to bet that many of you reading this article are still using old equipment that does not meet these new standards. And that means you are not recovering all of the refrigerant that you should, and you are not charging repaired systems with the correct amount of clean refrigerant.
In between classes, the event luncheons offered a chance to interact with other attendees and listen to great speakers, like Thursday’s keynote by Roy Gage.
Another valid point Sheffield raised was the proper method of ensuring all of the moisture is removed from a system before recharging. I’ve witnessed personally repairs where the accumulator (or receiver-drier) was not replaced as part of the repair. I’ve also seen systems that were not evacuated prior to charging a repaired system, ensuring that air would be present (resulting in higher pressures and lower cooling efficiency) and any moisture trapped in the system’s oil would remain there.
Sheffield pointed out two critical mistakes that are often made in the field. First, deciding on how long a system needed to remain in vacuum in order to successfully cause the moisture to vaporize and be removed (dependent on outside air temperature and amount of vacuum applied). Second, adding moisture to a system inadvertently by using PAG oil from an unsealed opened container. PAG oil is hygroscopic, absorbing water from the air if left open. Moisture in the system can lead to corrosion and damage to the mostly aluminum components that make up a modern air conditioning system.
Additionally, Sheffield commented on the importance of testing the system as outlined by the OEMs. Some makes require the doors open, hood closed. Some doors closed, hood closed. And some require testing with everything open. The only way to make sure your test results are accurate is to first review the test procedure in your service information system. He also stressed a point that bears repeating here. It is vitally important that oil and refrigerant charges remain in specification. Modern systems (made during the last 10 years or so) use much smaller oil and refrigerant charges and have less tolerance for error. Too much oil can act as an insulator inside the heat exchangers (condenser and evaporator) and impede the heat transfer necessary to effective system operation. Too little oil speaks for itself, resulting in catastrophic compressor failure that often spells expensive repairs requiring the replacement of related system components. Too much refrigerant results in lower cooling efficiency and higher pressures and temperatures in the compressor while too little refrigerant can impact oil flow through the system and cause a loss of cooling ability.
During his class, Sheffield also shared two techniques that he uses routinely for diagnosing A/C system performance. The first he shared was what drew me to his class in the first place: using a DSO and pressure transducers to aid in compressor diagnosis. The concept was simple enough. Compressors are mini-pumps, and their pumping cycles can be seen in the pressure signal picked up by the transducer. Sheffield made his own testing rig by adding pressure transducers to a standard gauge set and powering them independently.
Many cars have pressure transducers already incorporated into the system, so an DSO can be used to monitor the signal they produce. Much like low current testing on a fuel pump, Sheffield claims he can diagnose worn compressors, especially piston-type designs, using this method. And, like many other testing techniques that were first attempted, this technique is new enough to be interesting but not old enough to be proven.
Attendees put on their ‘back to school’ game faces for classes at the MACS event.
The second technique he shared was not “new” to some of us. That is the use of an anemometer to measure wind speed. This technique uses wind speed to check air flow through the condenser and/or from the panel vents. Users will have to use it on a lot of “known good” cars to get a feel for what numbers to expect, but it can be an effective way to show a customer why he needs to replace his cabin air filter without going through the effort of actually removing it. Restricted filters, or problems with blend doors and blower motors, can affect the amount of air being passed into the cabin (and across the evaporator).
More Training
These passages are pretty small. You sure that blow tip flush gun is going to clean out all the debris?
All that and more, and that was just the first morning session!
After lunch, I elected to attend a class deliverd by ACDelco’s Jerry Mungle. The focus of Mungle’s class was electronic control systems.
Mungle began his class with a statement that holds a lot of truth to it. Today, drivers don’t control their air conditioning systems, computers do. Selecting “A/C” on the dash is only asking a control module’s permission to get cool on a hot day. And the Electronic Control Unit (ECU) with the final say? It’s the Engine Control Module (ECM), and the reason why is pretty interesting.
Thursday evening’s reception featured a local jazz trio, and a mini-Mardi Gras celebration.
Compressors place a lot of load on the engine, and that reduces fuel economy and can increase tailpipe emissions. Anything that impacts either falls under the ECM’s control. Pushing the button on the Heating, Ventilation and Air Conditioning (HVAC) control head merely sends a request to the ECM, sometimes indirectly through a third module (typically, the Body Control Module, or BCM).
Troubleshooting these systems is as much about understanding how to use a scan tool as it is pressure gauge interpretation. Mungle strongly suggests that any A/C electronic troubleshooting session start out with a complete system scan, looking for codes in every module on the car. Often, seemingly unrelated codes can lead to the system fault, especially if the problem involves a communication issue between modules.
A traditional, and looked forward to, part of the MACS conference is Ward Atkinson’s State of the Industry presentation.
Along the way, Mungle shared some interesting automotive trivia. For example, did you know that a “stretchie” belt is nothing of the kind? For those that don’t know, a “stretchie” belt is the serpentine belt design that uses no tensioner assembly and requires special tooling to install. Many of us were led to think of these belts as big rubber bands, but when you think about it, that doesn’t make much sense. If I can stretch the belt to install it, how does it hold tension and why can’t I reuse it?
Mungle supplied the answer. The material used to make these belts shrinks when initially heated. After they have been run for a few minutes, they “shrink to fit.” Another tidbit shared by our instructor was the reason for the proliferation of so many electronic control units. The wiring they require is markedly less than the wiring that would be needed to perform the same functions if only one ECU were used. All this thanks to the capabilities of the Controller Area Network (CAN) protocol.
The trade show hours did not compete with class hours, so attendees didn’t have to miss a thing.
Mungle also told his attendees that more and more, A/C problems will be electrical rather than in the refrigerant circuit. Modern compressors are more robust than ever and systems are sealed so well, leakage is rarely a problem. So break out your scan tool and plug in to known good cars to get a feel for what normal data Parameter Identifiers (PIDs) look like so you’ll be ready when that broken car pulls into your bay.
The Rest Of The Week
Motor Age contributing editor and nationally renowned trainer Bernie Thompson shows the latest ATS product, the Bulls Eye leak detection system, to trade show visitors.
This recap was just from the classes I was able to attend on the first day of training, but that’s not all the MACS event had to offer. In addition to the classroom training, Ward Atkinson presented his annual State of the Industry address (which I refer to in this month’s Undercar feature) as well as an industry trade show featuring a wide array of vendors and aftermarket representatives.
As the technical editor, I get to attend and report on events like this one all over the country. Training events like this one get you thinking, ignites your thirst to learn more, and allows you the opportunity to focus on quenching that thirst. If you’ve never been to one, try to attend one near you in the next 12 months. You won’t regret it.
