How "pure" is your refrigerant? Do you know? Most technicians and do-it-yourselfers never question the purity of virgin refrigerant, and most assume the refrigerant in a vehicle is "pure enough" unless the A/C system is acting oddly or has a mysterious cooling problem. The cause may be contaminated refrigerant!
Everyone should be alert for possible refrigerant contamination. Contaminated refrigerant can cause cooling issues, harm your A/C system, and contaminate recovery equipment.
If contaminated refrigerant is accidentally pulled into a R-12 refrigerant recovery machine, it could cost a repair shop up to $300 or more to decontaminate their equipment (to replace the dryer and filter, and then vacuum purge for one hour). The contaminated refrigerant in the recovery tank would also have to be disposed of, which might be worth several hundred dollars depending on how much was in the tank.
An even greater danger is when a shop has no idea their equipment is contaminated, or that they are contaminating other vehicles they service in their shop.
HOW BAD IS THE CONTAMIANTION PROBLEM?
Nobody knows for sure how bad the refrigerant contamination problem really is. Some say the issue has been blown all out of proportion by alarmists or those who are promoting the use of refrigerant identifiers to the service industry. But a survey by the Florida EPA revealed some startling results.
The Florida EPA asked a cross-section of service outlets to voluntarily participate in a refrigerant study. There was no cost involved to the participants and there would be no "consequences" based on what was found. About a third of the service shops contacted declined to participate for various reasons, and nearly two-thirds of the used car dealers contacted also refused. Eventually, the Florida EPA tested the refrigerant in recovery tanks at about 100 service outlets.
Contamination of some sort was found in 38% of the recovery tanks overall! Independent repair garages and service shops had the lowest rate of contamination, but it was still 32% (nearly one out of three). Used car dealers were the worst, with 71% of their recovery tanks (almost three out of four) showing signs of contamination.
Air contamination was the worst problem, being present in 22% of the tanks tested overall. But cross-contamination between R-12 and R-134a was also found in 15% of the tanks. The most cross-contamination (29%) was discovered in used car dealers.
Air is something you do not want in an A/C system because it is a noncondensable gas. Air does not change from a vapor into a liquid at the kind of pressures that can be achieved by an ordinary compressor, so all it does it occupy space and displace refrigerant. The result is reduced cooling performance, evaporator freeze-up, intermittent cooling, increased compressor noise, higher than normal discharge pressures, and maybe even compressor failure.
Air can get inside an A/C system a couple of ways. Air enters the system anytime the system is opened for service. If the system is not vacuum purged prior to recharging, air may still be inside when the refrigerant is added.
Air can also enter through leaks. Even when the system contains refrigerant and is under pressure, some air and moisture will still get inside. The desiccant will take care of the moisture, but there is no way to get rid of the air short of removing and recovering the refrigerant and then pulling a strong vacuum on the system.
Another way that air often enters the system is when refrigerant is added. If the refrigerant tank on a charging station or recycling equipment contains air, it will enter the vehicle along with the refrigerant. Some recycling machines are designed to automatically vent trapped air from the recovery tank while others require this job to be done manually. Once a day is recommended to maintain the purity of the refrigerant. But some technicians are not as meticulous as others, and most older equipment does not automatically purge the tanks as well as it should. Consequently, air contaminated refrigerant is a common problem.
To check for air contamination, a shop technician should note the pressure on the refrigerant recovery and storage tanks to see if it exceeds the maximum allowable pressure for a given ambient temperature. If it does, there is air in the tank and the tank needs to be purged before the refrigerant can be used.
The worst part about air contamination is that it is difficult to diagnose. Some refrigerant identifiers can detect air contamination but others cannot. Indicators of air contamination are higher than normal high side readings, compressor noise and intermittent cooling problems caused by evaporator freeze-up.
A properly functioning A/C system with a normal charge of uncontaminated refrigerant should blow air that is about 40 to 50 degrees colder than ambient temperatures. This will obviously vary with temperature and humidity, but should be a ballpark figure.
One example of how tricky air contamination can be to diagnose is on 1994-95 Cadillacs. On these vehicles, you may find a code A047 that indicates a low refrigerant level. Yet when you check the gauge readings, everything seems normal. Evacuating and recharging system may eliminate the problem, but if it comes back it means there is air contamination in your recovery tank. The cure, says Cadillac, is to evacuate and recharge the system using virgin refrigerant rather than recycled refrigerant.
WHY REFRIGERANT CONTAMINATION IS HAPPENING
Cross-contamination is on the rise for a variety of reasons. One is that we have moved from a single refrigerant market to a multi-refrigerant market. In addition to R-12 in older vehicles, R-134a in cars built since 1996, and R1234yf in a growing number of new vehicles, alternative refrigerants are found in many auto parts stores. These include blends such as Freeze 12, FRIGC, Free Zone, Hot Shot, McCool Chill-It GHG-X4 and R-406A. Millions of pounds of this stuff have been sold to consumers.
NOTE: These alternative refrigerants are for older R-12 systems only. They must NOT be used in newer vehicles with R-134a or R1234yf A/C systems.
The high price of virgin or recycled R-12 has been the real driving force behind the proliferation of alternative refrigerants and contaminated products. High prices have encouraged some people to smuggle in bootleg R-12 from offshore (numerous arrests have been made, and law enforcement officials say more will be made). Others are seeking easy profits by diluting virgin or recycled R-12 with other less expensive refrigerants (such as R-22).
Cylinders of counterfeit Allied Signal Genetron R-12 have reportedly turned up in various parts of the country. The cylinders do not contain R-12 but some "unknown" refrigerant. Allied Signal says the counterfeit boxes do not have cut-outs where lot numbers strapped on cylinders would appear and there are no bar codes or white painted stripes on the sides. The number "Q 1167" may also appear on the bottom of the packaging. The cylinders themselves may be marked with a pressure-sensitive decal whereas the genuine product has markings printed on the cylinder itself.
The high price of R-12 has also lead some people to use illegal flammable refrigerants. Consequently, more and more "junk" is turning up in air conditioning systems and causing problems not only for motorists but also those who attempt to abide by the law and recover and recycle the refrigerant for use in other vehicles. Like a bad virus, contaminated refrigerant is being spread from vehicle to vehicle now that recycling is required for R-12 and R-134a.
CONCERNS ABOUT REFRIGERANT CONTAMINATION
Concerns about cross-contamination were first voiced when it became clear that new vehicles would be converted to the new "ozone-safe" R-134a refrigerant, so chosen because it was deemed the best alternative at the time. R-134a's cooling characteristics closely match those of R-12, and it is nontoxic, nonflammable and environmentally acceptable. Starting in 1992, the first cars with the R-134a hit the street. During the next two years, the OEMS converted more and more of their vehicles so by 1995 virtually all car and truck A/C systems were R-134a.
To minimize the risk of cross-contaminating these two refrigerants, the EPA required different service fittings for R-134a and labeling so technicians could identify the type of refrigerant in a vehicle. Unique service fittings are also required for all other alternative refrigerants. But with many R-134a vehicles out of warranty, there has been a growing problem with refrigerant cross-contamination.
Alternative refrigerants must meet the Environmental Protection Agency SNAP (Significant New Alternatives Policy) criteria for environmental acceptability and usage. The SNAP rules prohibit flammable refrigerants or ones that contain ozone-damaging CFCs. For more information, see Flammable Refrigerants.
The only alternative refrigerant currently endorsed by the car makers is R-134a. They say R-134a can perform well in most R-12 systems when the proper retrofit procedures are followed, and because R-134a is not a blend of different refrigerants it will not "fractionate."
Fractionation is a separation of the ingredients that can occur in a blend caused by chemical differences between the refrigerants (lighter and heavier elements do not want to stay mixed), different rates of leakage through seals and hoses (smaller molecules leak at a higher rate than larger ones), and different rates of absorption by the compressor oil and desiccant. Fractionation can change the overall composition of the blend once it is in use, which can change the cooling properties of the blend. Fractionation also makes it difficult to recycle a blended refrigerant because what comes out of the system may not be the same mix that went into the system.
The OEMS also say limiting the alternatives to one (R-134a) simplifies things, reduces the risk of cross-contamination and eliminates the need for multiple recovery machines.
The suppliers of blends say their products typically cool better than straight R-134a in systems designed for R-12. Some also claim that it is not necessary to change the compressor oil or desiccant (which is usually recommended when converting an R-12 system to R-134a). They also say the fractionation problem is exaggerated and do not foresee any major problems with recovering and recycling their products (recycling blends is currently illegal, but the EPA is reviewing its feasibility).
Some refrigerants that have been introduced do not meet the EPA's criteria for environmental acceptability or safety. Flammable refrigerants that contain large quantities of hydrocarbons (propane, butane, isobutane, etc.) have been declared illegal for use in mobile A/C applications, but are still turning up in vehicle systems anyway because of their cheap price.
Flammable refrigerants pose a significant danger to a vehicle's occupants should a leak occur. A spark from a cigarette or a switch can ignite the leaking refrigerant causing an explosion and turning the vehicle's interior into an inferno. It only takes about four ounces of a flammable hydrocarbon refrigerant such as propane or butane to create an explosive mixture inside a typical automobile passenger compartment.
Frontal collisions can also release the refrigerant if the condenser is damaged, which could result in a severe underhood fire causing extensive damage to the vehicle.
Merely topping off an A/C system with a flammable hydrocarbon can make the entire charge of refrigerant flammable if the amount added exceeds a certain percentage: 10% in the case of an R-12 system and only 5% with R-134a! That is only three or four ounces of hydrocarbon depending on the overall capacity of the system.
Flammable refrigerants are used in some stationary applications as well as truck trailer refrigeration units because there is less risk of leakage or fire. Also, the amount of refrigerant is typically much less, only five or six ounces total instead of several pounds.
WHEN REFRIGERANTS MIX
Federal law prohibits the topping off of any A/C system (R-12 or R-134a or R-1234yf) with any other refrigerant. You must use the same type of refrigerant if the system is low on charge unless the system is being converted to a different refrigerant (in which case all the old refrigerant must be recovered prior to making the change).
R-12, R-134a and R1234yf are not compatible refrigerants because R-134a and R1234yf will not mix with and circulate mineral-based compressor oil (which may lead to compressor failure). Nor is R-134a compatible with the moisture-absorbing desiccant XH-5, which is used in many R-12 systems.
Intermixing refrigerants can also cause cooling problems and raise compressor head pressures dangerously. Adding R-22 (which is used in many stationary A/C systems but is not designed for use in mobile A/C applications) to an R-12 or R-134a system may raise head pressures to the point where it causes the compressor to fail. Straight R-22 can cause extremely high discharge pressure readings (up to 400 or 500 psi!) when underhood temperatures are high. R-22 is also not compatible with XH-5 and XH-7 desiccants used in most mobile A/C systems (XH-9 is recommended).
R-134a also requires its own special type of oil: either a polyalkylene (PAG) oil or a polyol ester (POE) oil. The OEMS mostly specify a variety of different viscosity PAG oils because some compressors require a heavier or lighter viscosity oil for proper lubrication (though General Motors does specify only a single grade of PAG oil for most service applications). The aftermarket generally favors POE oil because POE is compatible with both R-12 and R-134a and unlike PAG oil it will mix with mineral oil. Mineral oil, as a rule, should still be used in older R-12 systems.
To identify the type of refrigerant in a vehicle system, you can use any of the following:
Refer to the vehicle model year. The first R-134a systems were introduced in model year 1992 on a few models. The main transition occurred during model years 1993 and into 1994. By 1995, virtually all passenger car and light trucks were factory equipped with R-134a systems.Based on this, you might assume that any vehicle older than a 1992 model would be an R-12 system and that any built since 1995 would be R-134a. Such an assumption would be mostly true, but there is always the possibility that an older vehicle might have been converted to R-134a or recharged with some other refrigerant.
Refer to the vehicle manufacturer's reference or service information decal under the hood. On newer vehicles, the decal should specify if the system is R-12, R-134a or R-1234yf. The decal may also specify the refrigerant and lubricant capacity of the system. Such information is most helpful when it is provided, but on older vehicles there may be no decal or the factory decal may be missing. Or, the vehicle may have been charged with who-knows-what (maybe by an unscrupulous used car dealer) to get it to blow cold air (at least temporarily). Converted vehicles are supposed to have the proper service fittings installed, but not everyone follows the rules.
Check the service fittings. R-12, R-134a and R-1234yf systems are equipped with different types of service fittings to minimize the risk of cross-contamination of refrigerants and lubricants: R-12 systems have a 7/16 inch threaded schrader valve type service fitting on the low pressure side, and a 3/8 inch threaded schrader valve type service fitting on the high side. R-134a systems have a 13 mm quick-disconnect service fitting on the low pressure side, and a 16 mm quick-disconnect service fitting on the high pressure side. Other refrigerants are supposed to have different fittings from these. So if a fitting does not appear to be one for R-12 or R-134a, it is probably something else.
The best defense against the unknown and the risks of cross-contamination, adulteration or flammable refrigerants is for shop's to use a refrigerant identifier. The equipment will tell the technician if the refrigerant is is pure (acceptable) or contaminated (not acceptable). Some identifiers will show a percentage breakdown of the various ingredients, which can help identify hydrocarbons as well as unknown blends.
An identifier should be used to test a vehicle prior to hooking up a refrigerant recovery machine, to check the quality of recovered and recycled refrigerant, and to check the quality or purity of "virgin" containers.
The four basic methods of identifying refrigerants used in detection equipment include:
Chemical Dissociation. This method uses an ultraviolet lamp to measure the amount of chlorine within a sample. This will reveal the level of R-12 in a sample, but does not detect hydrocarbons (flammables).
Acoustic Resonance. This method is based on the principle that sound travels at different speeds through different refrigerants. By measuring the velocity of sound through a sample, the unit can measure within 5% the purity of the refrigerant. It also is capable of detecting hydrocarbons.
Infrared Spectrum. The theory behind this method is that different refrigerants have different wavelengths within the infrared light spectrum. The unit works similar to an infrared exhaust analyzer to identify the presence of R-12, R-134a and R-22. Purity can be measured with 98% accuracy. Percentages of each refrigerant are then displayed. The unit can also detect hydrocarbons (some units will sound an audible alarm if hydrocarbons are detected in the sample).
Thermo Conductivity. Each refrigerant dissipates heat at a different rate. By measuring the rate of heat dissipation in a sample, the unit can give a go-no go indication of the type of refrigerant (R-12 or R-134a) if the same is at least 98% pure. This type of unit does not detect hydrocarbons or display percentages of concentration, but is very simple and inexpensive compared to the others.
The advantage of using equipment that measures actual concentrations of the refrigerants in the sample is that it allows you to see what exactly is in the refrigerant. There is no way to separate one type of refrigerant from another in a shop environment, so all contaminated refrigerant regardless of the level of contamination must be disposed of to prevent cross-contamination of recovery and recycling equipment as well as other vehicles.
Identifying blends is not as easy as identifying pure R-12 or R-134a because most identifiers have limited capabilities. The percentages shown may not correspond to what is actually in the system when blends are involved. Some equipment suppliers have reference charts to identify a blend by its characteristic fingerprint. But as mentioned earlier, fractionation may change the makeup of the refrigerant resulting in a different fingerprint.
OTHER WAYS TO IDENTIFY REFRIGERANT
Using a gauge set to identify the refrigerant in a vehicle system only works if the system has relatively pure R-12 or R-134a in it. It does not work so well if the two refrigerants are intermixed or if the system has a low charge or is contaminated with other substances (such as hydrocarbons). Even so, if you think someone has converted an R-12 system to R-134a, higher than normal high pressure gauge readings would probably confirm your suspicions. Likewise, if you think someone may have charged an R-134a system with R-12, lower than normal high pressure side gauge readings would be present.
An electronic leak detector can tell you if R-12 or R-134a is present, but it will not tell you if the refrigerant is pure. Older R-12 leak detectors sniff for chlorine, which is absent in R-134a so an R-12 leak detector should not react in the presence of R-134a. If you get a reaction on a vehicle or bulk container that is supposed to contain R-134a, it would tell you the refrigerant is cross-contaminated.
HANDLING & DISPOSAL OF CONTAMINATED REFRIGERANTS
Getting rid of contaminated refrigerant currently requires sending it to an approved processor for recycling or destruction (it is illegal to vent it into the atmosphere). R-12 gives off toxic gases when burned, so it must be incinerated under closely controlled conditions or broken down chemically.
More Air Conditioning Articles:Troubleshooting Air Conditioning Problems
New Refrigerants & A/C Systems
California proposes ban on R134a sales to motorists
Retrofitting older vehicles with R-12 A/C systems to R-134a
MACS Recommended A/C Service Procedures (PDF file - requires Adobe Acrobat Reader to view).
Automatic Climate Control
A/C Compressor Failures
A/C Condenser Flushing
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