Old Problems, New Technologies Cap the 2002 MACS Show

Every year members of the Mobile Air Conditioning Society (MACS) get together and discuss a wide range of topics that are of interest to those who make their living servicing automotive A/C systems. This year’s event was held Feb. 18-21 in Las Vegas.

For the past several years, many of the technical sessions that were offered were focused on retrofitting older vehicles with R-12 A/C systems to the new "ozone-safe" R-134a refrigerant. But this year, there was hardly any discussion of retrofit at all. The reason? Retrofit has become a non-issue.

R-12 has almost disappeared from the market - except for the residual refrigerant that can still be recovered and recycled from older vehicles, and that which is still being smuggled into the U.S. from offshore sources. When an older R-12 system loses its charge or needs major repairs, most shops are going ahead and converting these systems to R-134a - which is creating a new problem for the environment.

The Greenhouse Gas Issue
Though R-134a is nontoxic, nonflammable, contains no chlorine and it does not breakdown the Earth’s ozone layer that helps block the sun’s harmful ultraviolet radiation, it is a "greenhouse" gas that contributes to global warming. The U.S. Environmental Protection Agency says R-134a has a global warming potential that is 1,300 times greater than carbon dioxide (CO2)!

CO2 is a major issue with environmentalists because the rising level of CO2 in the atmosphere over the past century is causing a gradual rise in average worldwide temperature and adverse changes in world climate patterns. The problem, they say, is that CO2 retains heat. This creates a "greenhouse" effect that traps heat in the atmosphere and allows it to build up over time. The rise in CO2 has been directly linked to the increased use of fossil fuels in industrialized countries and the increase in the world’s vehicle population. Motor vehicles account for about 20% of the overall CO2 problem. But a much larger portion (perhaps 50% or more) of the global CO2 problem is due to deforestation and "slash-and-burn" agricultural practices in many Third World nations. Even so, the role played by motor vehicles is significant.

We now have 738 million cars and light trucks on the world’s roads, plus another 200 million commercial vehicles. By the year 2010 or sooner, the world’s vehicle population of cars and light trucks is expected to number more than 1 billion! Of these, 84% will have factory-equipped air conditioning. Multiply the number of vehicles times the amount of refrigerant each contains (that will leak out or have to be replaced during its lifetime) and it adds up to a lot of greenhouse gas.

A meeting in Kyoto, Japan two years ago produced a proposal that calls for reducing worldwide CO2 emissions. But the proposed reductions would require drastic changes in industrialized nations, including major cutbacks in fuel usage. Since America is so dependent on motor vehicles and isn’t about to curtail its love affair with SUVs, the United States has not signed the Koyoto Protocol. Even so, many European nations are moving ahead with changes in technology that will soon impact our automotive service industry whether our government chooses to participate in the Kyoto Protocol or not.

As long as R-134a or any other refrigerant remains sealed inside an A/C system, it poses no environmental hazard. But if it leaks out, it remains in the atmosphere a long, long time and contributes to the global warming problem. According to new research that has been conducted by the Environmental Protection Agency, measurable amounts of R-134a are now being detected that indicate roughly 40 million pounds of R-134a a year is somehow finding its way into the atmosphere. Forty million pounds of refrigerant is the equivalent of 53 million 12-oz. cans. That’s a huge amount of refrigerant!

The trouble is, nobody seems to know how all this refrigerant is ending up in the wrong place. The number of new vehicles on the road today that have R-134a A/C is now roughly equal to the number of older vehicles with R-12 A/C. But the newer R-134a systems are tighter, leak far less, have smaller refrigerant capacities and go a lot more miles before they require service. So most of this refrigerant probably is not coming from newer vehicles.

Some blame do-it-yourselfers who can walk into any auto parts store and buy cans of R-134a to recharge a leaky A/C system. Recharging a leaker is only a temporary fix, and sooner or later the new refrigerant leaks out - which means another recharge and more pounds of refrigerant that eventually end up in the atmosphere.

Several states including California, Florida and Wisconsin have passed laws prohibiting professional installers from recharging A/C systems that are known to be leaking. But only Wisconsin’s law still remains in effect. The others have been rescinded.

Because noncertified individuals can’t legally purchase small cans of R-12, many DIYers assume R-134a will work just the same and add it to their older R-12 systems. It does work - for awhile. But unless they do a retrofit and add the proper compressor lubricant, all they do is create a cross-contamination problem and shorten the life of their compressor.

Some within the A/C industry say all small cans of refrigerant should be banned for DIYers as well as professionals. Why? Because studies have found that when charging an A/C system with individual 12-oz. cans, approximately 10% of the can’s contents end up being vented into the atmosphere. And if the charging procedure only uses part of a can, the rest of the refrigerant in the can is often allowed to escape when the can is disconnected from the charging hose. Besides, using individual cans of refrigerant is not a very accurate way to recharge A/C systems. Charging from a 30-lb. jug is a much more accurate process because you only use the amount of refrigerant you need. The rest remains in the jug and very little escapes when connecting and disconnecting charging hoses.

Used car dealers who recharge leaky A/C systems but won’t spend a dime on repairs are another culprit who add to the problem. So too are small repair shops (particularly collision repair shops) who do A/C repairs but do not have the required recovery equipment to capture residual refrigerant from vehicles. In addition, those who illegally vent cross-contaminated or unknown refrigerants because they don’t know how to properly recover and dispose of the stuff are contributing to the overall problem.

Federal law currently prohibits the venting of any refrigerant, including R-12, R-134a or any other substance that ends up inside an A/C system. Federal law requires that all refrigerants be recovered when service is required, which means you must have a separate recovery machine for each type of refrigerant you’re handling. Since very few shops have a third machine for dealing with blended or contaminated refrigerants, they either have to turn the customer away or illegally vent the unwanted refrigerant.

Venting continues to be a major issue in the rest of the world. As the worldwide vehicle population continues to grow, many countries have yet to adopt any kind of service standards that require recovery and recycling. What’s more, R-12 is still widely available in much of the rest of the world. In fact, many new vehicles that are being sold in these countries today are being charged with R-12. But that’s another issue. Most of the R-134a that’s being used worldwide is being used in North America, western Europe and Japan.

Big Changes Coming
In response to the many concerns that have been voiced over global warming, the Europeans will host a meeting in February 2003 that may decide the future direction of A/C technology, not only in Europe but worldwide. One proposal that’s being seriously considered would be the phase-out of R-134a in favor of a new, more environmentally friendly refrigerant called R-744.

The new R-744 refrigerant is actually plain old carbon dioxide. Though CO2 is a greenhouse gas, its global warming potential is insignificant compared to R-134a. It’s also nonflammable and nontoxic (as long as it isn’t allowed to build up to excessive levels inside the passenger compartment of a vehicle). Its only drawback as a refrigerant is that it requires extremely high pressures. We’re talking operating pressures of 1,500 to 2,000 psi or higher! This can create a very unfriendly situation for the hapless technician who accidentally pulls off a high pressure hose on a CO2 A/C system.

As development of the new CO2 A/C systems move ahead (there are currently about 30 vehicles with prototype CO2 systems being evaluated by various auto makers worldwide), safety will obviously be a major consideration. Blow-out disks that can relieve pressure will be located throughout these systems. A whole new generation of service equipment will also have to be developed for charging and testing high pressure CO2 systems. Nobody yet has figured out how to test for CO2 leaks, let alone developed any CO2 service and repair procedures. But all that will come in due time.

Because of the lead time that’s required to get a new technology into production, we probably won’t see any new high pressure CO2 A/C systems for a few years yet. But DaimlerChrysler announced it will have the first R-744 systems in production in Europe by model year 2006.

Other items that may also be on the agenda for the upcoming European A/C summit include establishing minimum efficiency requirements for A/C systems, possibly taxing A/C systems to discourage A/C as an option or even banning the use of A/C in private passenger cars altogether!

A/C usage in Europe has traditionally been much lower than that in the U.S because of the higher price Europeans have to pay for fuel. Even so, the popularity of factory-equipped A/C in Europe has been growing rapidly in recent years, which is having a negative impact on overall average fuel economy. Some scientists and bureaucrats there would like to see this trend curtailed or even reversed.

The Europeans are pushing for a 25% increase in their average fuel economy by 2008, which would put them far ahead of the U.S. but also require significant changes in both A/C and engine technology (more high efficiency direct injection diesel and gasoline engines, hybrid electric vehicles and eventually fuel cells). As we’ve learned from past experience, changes in automotive technology that happen there will eventually happen here, too. We’ve seen it with front-wheel drive, fuel injection, rack & pinion steering, antilock brakes, high intensity headlamps, side air bags, etc., etc., etc. There’s no reason to believe A/C will be any different.

Automatic Temperature Control
Another change in A/C technology that is already having a big impact on the aftermarket is automatic temperature control (ATC). Designed to make life easier for the vehicle’s occupants, the complexity of many of these systems is making life anything but easy for technicians who have to fix them.

Automatic temperature control systems have been around for many years, but with each passing model year the complexity of new systems has continued to grow at an exponential rate. The climate control system is now so intertwined with the powertrain control module, body control module and other system modules that it’s difficult to figure out what might be causing an A/C cooling problem.

In the good ol’ days, you just turned or flipped a switch to turn on the A/C. The switch sent voltage to a relay that energized the clutch on the compressor. Fan speed was selected manually with a knob while temperature control was controlled manually by cables or vacuum motors that operated the blend, recirc and duct doors.

Now you don’t even have to turn the A/C on. It automatically comes on as soon as the engine is started. You just preselect a temperature setting and the ATC system does the rest. It provides heat when the vehicle is cold, and cool air when the vehicle is hot. It selects the blower speed as well as where the air exits the ducts. What’s more, we now have "dual zone" A/C systems that provide separate temperature settings for the driver and front seat passenger, as well as front/rear systems that have separate controls for the rear passengers in minivans and SUVs.

Some of these ATC systems have "smart" control heads that contain the decision-making electronics that regulate system operation. Others have a "dumb" control head that just passes the driver settings on to a second module (typically the body control module) that actually carries out the commands. Both kinds of heads can be very expensive to replace (up to $2,000 or more on some vehicles!). Dumb heads typically have four to eight wire connectors while smart heads usually have connectors with 20 or more wires.

On many vehicles, the powertrain control module has the final say as to whether or not the A/C will provide any cooling. The PCM controls the relay that energizes the A/C compressor. It will turn on the A/C compressor when it receives a request from the ATC module or body control module - but not under certain operating conditions. The PCM may not turn the A/C compressor on if other sensors tell it the engine is overheating, the throttle is wide open or idle speed is dropping because of demands being placed on the engine by other accessories.

In addition to the control head, ATC systems also use a variety of sensors to monitor temperatures as well as what’s happening in various parts of the system. The two basic types of sensors are thermistors that change resistance to monitor the ambient, interior, outlet, evaporator and refrigerant temperatures, and feedback sensors that monitor the position of air door control motors. Some newer vehicles now use infrared sensors that read the surface temperature of the vehicle’s occupants in the front or rear seats, and many others have "sunload" sensors that allow the ATC system to compensate for the extra warmth created by direct sunlight.

Some systems now use compressor rpm sensors to detect belt slippage that could indicate a compressor is on the verge of failing. Others use pressure sensors to monitor the refrigerant.

Most (but not all) of the newer ATC systems also have moved away from vacuum motor actuated blend and duct doors to electric motor controlled doors. There are three basic types: three-wire "smart" motors that keep the ATC module informed of their relative position, five-wire smart motors that do likewise and five-wire dumb motors that require a separate position sensor. On some systems, the ATC control module counts the pulses of the motor commutator to determine its relative position. This may require a special self-calibration procedure if any of these components are replaced so the ATC module can relearn the correct position of the motors and doors.

Troubleshooting problems in these new ATC systems requires a scan tool on most vehicles, though some can provide diagnostic trouble codes through the control head by pushing various combinations of buttons simultaneously or in a certain sequence. Either way, the technician needs a thorough understanding of how the system is designed to operate along with a wiring diagram, diagnostic charts and test procedures needed to repair the system. The problem is, many aftermarket scan tools don’t have as much of the ATC info or capabilities as the new car dealer scan tools. Some vehicle manufacturers (notably Mercedes-Benz) also have been very slow to release their latest service information to the aftermarket. Hopefully, this situation will change as a result of legislation that requires the vehicle manufacturers to release OBD II-related service information to the aftermarket.