A/C Update

A/C Update

The Mobile Air Conditioning Society (MACS) 25th Anniversary Convention and Trade Show is a great event for shop owners and technicians to learn about the latest trends in air conditioning technology and to see the latest A/C service products and equipment. This year’s show was held in Las Vegas February 1-3.

One question that came up repeatedly at this year’s technical meetings was the future of R-134a as a refrigerant. Environmental concerns have now shifted from worries about ozone depletion to worries about global warming. Consequently, automotive refrigerants are back in the crosshairs once again.

Back in the mid-1990s, vehicle manufacturers in this country were forced to discontinue the use of R-12 because it contained chlorine, which was being blamed for thinning the Earth’s protective ozone layer. The OEMs switched to R-134a because the new refrigerant contained no chlorine and was EPA-approved as being “ozone safe.”

But R-134a is also a potent “greenhouse gas” that can contribute to global warming. The molecules of R-134a trap and retain heat very efficiently, which makes it a good refrigerant. But this quality also gives it a global warming potential 1,300 times higher than carbon dioxide, which is the main gas everybody is concerned about these days. (CO2 is produced by the burning of fossil fuels as well as slash-and-burn deforestation, so developing countries are just as guilty of pumping millions of tons of CO2 into the atmosphere as are the industrialized countries.)

To address this problem, a growing list of nations, including most of Europe, have signed an international agreement called the Kyoto Protocol. Simply put, the goal of this pact is to reduce global emissions of greenhouse gases to 5% less than what they were in 1990 by the year 2012. Many scientists say the increase in CO2 in the atmosphere (which has been thoroughly documented) is trapping heat and is causing a gradual rise in worldwide temperatures – which could have a catastrophic impact on weather and trigger global flooding if the polar ice caps melt.

The United States has not signed this agreement because of the negative impact it would have on our economy and our way of life (we might have to give up gas-guzzling SUVs and actually do something to significantly reduce smoke stack emissions from coal-burning utility plants). Even so, President Bush has asked industry and utility companies to voluntarily reduce greenhouse gas emissions 18% by 2012.

Next Generation “Enhanced” R-134a Systems
In an effort to meet the President’s objective, the domestic vehicle manufacturers and the Society of Automotive Engineers (SAE) have launched an new initiative called “I-MAC,” which stands for Improved Mobile Air Conditioning. Essentially, I-MAC will lay the groundwork for next generation “enhanced” R-134a A/C systems that will be produced in the next few years. The goals of the I-MAC program are:

  • To reduce refrigerant leakage 50% compared to current A/C systems. This will require the use of improved seal designs, hoses and O-ring connections.

  • To improve the operating efficiency of A/C systems by 30%. This will require even more efficient condensers and evaporators, greater use of variable displacement compressors, and improved control logic that can maximize cooling performance while reducing power consumption.

  • To reduce the cooling requirements inside the passenger compartment 30%. This may involve using reflective coatings on glass to reduce sun loading, using lighter colored paints and interior plastics that reflect rather than absorb heat, and venting the interior to reduce heat buildup during hot weather.

  • To reduce refrigerant loss during service by 50%. This will require new specifications for service fittings, recovery/recycling/recharging machines, and new service hoses and gauges.

  • Improved leak detection. New leak detection requirements may be reduced to 4 grams (1/7th ounce) per year. Current standards require equipment to detect leaks of 1/2 oz. per year.

  • Improved recharging accuracy. As A/C systems are downsized and charging capacities are reduced, charging accuracy becomes more important than ever before. New charging equipment may be required to charge within 3 oz. or less of specifications.

The average passenger car system capacity in 2000 was 26.8 oz. Today, the average capacity is only 24.3 oz. Some new cars (Honda and Saturn, for example) only hold about 13 to 15 oz. of refrigerant.

A low refrigerant charge hurts cooling performance and may cause inadequate compressor lubrication and possible evaporator icing. It makes the system work harder and run hotter, which lead to premature compressor failure.

Overcharging can be just as bad. Too much refrigerant reduces cooling performance and, if there is also air in the system, may even create a potential explosion hazard under certain conditions.

Alternative Refrigerants
If the I-MAC program succeeds in meeting its goals and making future R-134a A/C systems more efficient and leak resistant, there should be little or no need to make yet another major change in refrigerants. After all, greenhouse gas emissions that can be attributed to mobile air conditioning sources are less than a fraction of 1%. That’s almost nothing compared to CO2 from other sources.

But the future is uncertain, and politics are hard to predict so the OEMs are continuing research and development of several alternative refrigerants. Primary among these are carbon dioxide (CO2), HFC-152a and secondary loop A/C systems that use a flammable hydrocarbon (such as propane) in the engine compartment, but use a heat exchanger to chill ordinary coolant for the passenger compartment.

In Europe, it appears the vehicle manufacturers are all moving toward CO2 for their next generation refrigerant. Changing to CO2 (also called R-744) requires a complete re-engineering of the A/C system because of CO2’s significantly higher operating pressure (as high as 2,000 psi!).

The exact time table for phasing out R-134a in Europe and introducing CO2 is still up in the air, but the first production systems will probably be introduced around 2010. The European regulations currently call for vehicle manufacturers to switch to a new refrigerant January 1, 2011, with a complete phase-out of R-134a by 2015 to 2016.

The Europeans are also calling for tighter R-134a systems, with leakage not to exceed 40 grams/year for a single evaporator system, or no more than 60 grams a year for a dual evaporator system. Service facilities will also be required to have trained and certified A/C technicians (just like we do now), and “gas-and-go” recharging without fixing leaks will not be allowed. The Europeans say they are also going to ban the sale of R-134a in small cans (something many U.S shops would like to see here to discourage do-it-yourselfers from recharging leaking systems or cross-contaminating refrigerants).

CO2 will work as a refrigerant, but it does not cool as effectively as R-134a when ambient temperatures are high. Nonetheless, it may cool well enough for European drivers because their climate is not as hot as ours.

New legislation in our own country that may impact future refrigerants has already been passed in California. Bill 1493, which was passed in September 2004, is aimed at reducing the global warming pollution from 2009 model year vehicles. The bill calls for reduced direct emissions (refrigerant leaks) and “indirect” emissions (CO2 in the exhaust) through the use of improved A/C systems or alternative refrigerants. Canada and several northeast states may also adopt these same regulations, which might force the domestic OEMs to change to CO2 or HFC-152a if enhanced R-134a systems can’t meet the new goals.

The EPA’s Position
The U.S. Environmental Protection Agency (EPA) is currently reviewing safety requirements for future CO2 and HFC-152a A/C systems, and will publish its findings soon. Both refrigerants pose a potential safety hazard to vehicle occupants as well as service technicians, CO2 because of its high operating pressure and HFC-152a because it is slightly flammable. In the event of a leak inside the passenger compartment (following an automobile accident, for example), some means of quickly venting the refrigerant would have to be provided to prevent possible suffocation (CO2) or cremation (HFC-152a) of the vehicle’s occupants.

SAE is also working to develop new standards for alternative refrigerant service fittings, leak detection, service procedures and equipment should these new refrigerants be used at some point in the future.

Compliance Issues
Jeanne Briskin of the EPA reminded those attending the MACS convention that any shop that performs A/C repairs (including just topping off the system) must comply with all the regulations found in Section 609 of the Clean Air Act. This includes:

  • Certifying A/C technicians in the techniques of recovery and recycling through an EPA-approved course.

  • Using the proper recovery/recycling equipment.

  • Absolutely no venting of any refrigerants (R-12, R-134a or “unknown” refrigerants).

  • Installing the required fittings, high pressure cutout switch and label when retrofitting R-12 systems to R-134a.

  • Not using flammable hydrocarbon refrigerants.

  • Keeping records of A/C service work for EPA inspection.

The penalty for not complying with these regulations can be as high as $32,500 per day!

For further information, you can visit the EPA’s website at:


Consumers can also report potential violations to:


The EPA’s “Significant New Alternatives Program” (SNAP) covers the use of alternative refrigerants for replacing R-12, and prohibits the sale of R-12 to non-certified persons. But to date, the EPA has not banned the sale of R-134a in small cans to do-it-yourselfers and has no immediate plans to do so. The EPA is studying the impact of residual refrigerant that escapes from small cans after they have been used (called “heel” emissions), and this may change its current attitude toward banning small cans.

Many of those who attended the MACS show said the EPA should ban the sale of R-134a in small cans to discourage DIYers from mixing refrigerants and recharging leaking systems. Shop owners say refrigerant cross-contamination is rampant and that many of the vehicles they see have been haphazardly retrofitted (no labels, wrong service fittings, mixed refrigerants, etc.). There’s no way to tell what kind of refrigerant might be in a vehicle, so it’s virtually mandatory these days to use a refrigerant identifier before attempting to recover or service a customer’s A/C system.

A/C Service Tips from MACS
Electrical diagnosis is often as much a part of service today’s A/C systems as the refrigeration circuit. Dan Dick, a MACS trainer, says a scan tool is one of the most useful tools for this kind of work.

“Why use chopsticks when you have a fork?” he says. In other words, why do electrical diagnosis the hard way when there is a much easier way to diagnose problems.

When confronted with an electrical problem in the A/C system, the first thing to do is “test, don’t guess.” Don’t jump to conclusions and don’t assume the system has only one fault. Electrical failures often occur in groups. If a fuse is blown, it probably failed because of an overload or short in the wiring, relay or other component.

Dick says he charges $39.95 to hook up a scan tool when diagnosing A/C problems. “Just like a doctor, I charge for each step in the process. I charge for the diagnosis, I charge for the part and I charge to install the part.”

Dick says to check the basics first, things such as the fuses, wiring, connectors and relays. Then hook up a scan tool and look at the A/C system data. Most scan tools can provide a wealth of information, including the status of the A/C compressor clutch, the status of fan relays, coolant temperature, even A/C high- and low-side pressures on many vehicles.

Next, study the vehicle’s wiring diagram. Trace the power flow from the battery though any switches or relays to the component and ground.

Cooling fan circuits are especially important because a fan or fan relay failure can cause the compressor to overwork, overheat and fail. The typical fan circuit includes a temperature sensor, a relay, a control module and the fan motor. The relay is the item that fails most often, so be sure to test the relay as well as its power supply and ground connections.

A good relay coil will typically read 40 to 80 ohms. If resistance is high, the coil may still be working but it is failing, or it may not work when electrical loads are high. If the coil has no resistance, it is open and has failed. Replace the relay.

Another simple relay test is to shake it. If you hear something rattling inside, the relay armature is probably broken.

There are three basic types of relays:

  • Normally open are the most common type. The armature closes when the coil is energized to route power to the fan motor.

  • Normally closed. The armature is normally closed and is pulled open when energized.

  • Dual relay. This type conducts current when open and when closed in two different circuits.

Some Pattern Failures:
Some vehicles with a history of cooling fan relay failures, according to Dick are:

  • Chrysler minivans (late 1980s and early 1990s). These use a solid state relay for the cooling fans, and the relays tend to overheat and fail.

  • Chrysler Neon. The problem here is the cooling fan circuit uses a radio frequency filter mounted on radiator fan shroud. The filter is mounted in a hot area and tends to fail, preventing the cooling fan from operating.

  • On most Chrysler vehicles, the cooling fan relay must be engaged before power can go to the A/C clutch. If the fan relay has failed, it will prevent the compressor clutch from engaging and there will be no cooling.

  • Ford cooling fan controllers (late 1980s and early 1990s Mustangs and other models). The controller contains a fan primary relay, A/C fan control relay, and wide open throttle cutout all built into one unit. The controller is supposed to switch on both fans when the compressor clutch is engaged. The problem is the two fan motors pull so much amperage that they rob voltage from the clutch. Consequently, the compressor clutch may only get 9.8 volts instead of full battery voltage causing it to slip, overheat and fail. The cure here is to add a separate relay for the compressor clutch so the clutch can draw full voltage from the battery.

  • Ford integrated relay control module (IRCM) (introduced in 1986). This unit controls the both fan relays, compressor clutch relay and the fuel pump relay. The module is mounted on the radiator shroud and is exposed to a lot of heat so failures are common. One symptom here of a failed module is a car that cranks but won’t start because the fuel pump isn’t getting any power through its relay. A failed module may also prevent one or both fans from operating, or the compressor clutch from engaging. The IRCM module also provides two-speed (high and low) fan operation by using an internal resistor to drop voltage to the fans. This resistor often burns up and fails. If any of the subsystems inside the IRCM module have failed, the whole module must be replaced.

  • Chrysler LH cars (since early 1990s). These vehicles use two relays (low fan and high fan), and two fans. Three fuses in the power distribution box protect these circuits. The engine control module provides ground to the fan relays when cooling is needed, and a dropping resistor is located inside each fan motor for two-speed operation (that’s why each motor has two power input terminals but only one ground terminal). At 238

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