The 23rd annual Mobile Air Conditioning Society (MACS) Worldwide convention was held Jan. 30 to Feb. 1 in New Orleans with record attendance. MACS’s staff reported that the show was attended by more than 2,000 exhibitors, shop owners, technicians and presenters, including visitors from 17 countries around the globe.
The technical presentations covered a wide range of subjects, a few of which we are reporting on to help make future A/C service a "Big Easy" job for your shop.
Future A/C Systems
Ward Atkinson’s presentation on the future of mobile A/C systems revealed some interesting information about what’s happening in Europe and how it will impact North America. The Europeans are moving to phase out R-134a as a refrigerant because it is on the hit list of gases that contribute to global warming. Most of the European nations signed the Kyoto Protocol that calls for cutbacks in carbon dioxide emissions and the release of other global warming gases. The U.S. did not sign this agreement, so it is uncertain how this will impact us. But within the next five to eight years, the Europeans will probably start introducing higher pressure CO2 (R-744) A/C systems on high-end luxury cars.
The advantage of using CO2 as a refrigerant is that there’s no net increase in global warming gases. The drawback is that a CO2 system operates at extremely high pressure - 1,500 psi on the low side and 2,500 psi on the high side. This requires much stronger tubing and poses a hazard to service technicians.
An interesting note on our environmentally sensitive European cousins is that currently they do not recover or recycle R-12 or R-134a when servicing vehicles. They are only required to do so when a vehicle is scrapped. In other words, they are still venting thousands of tons of refrigerant into the atmosphere - as do technicians in almost all Third World countries. Kind of makes you wonder why they all signed the Kyoto Protocol, and we didn’t.
Another alternative refrigerant that is being considered is HFC-152, which is slightly flammable. It may be used in a "secondary loop" A/C system that uses a heat exchanger to transfer cooling from the refrigerant in the engine compartment to ordinary antifreeze coolant that is circulating into the passenger compartment.
In the near future, Atkinson said we will see even more electronics in A/C systems, including more computer-controlled variable-displacement compressors, electronic orifice tubes and expansion valves, and electric-driven compressors in vehicles that have an idle shut off system to reduce fuel consumption.
Compressor Failures
Several presentations dealt with the subject of compressor failures. Delco reportedly examined 75 compressors that had failed and were returned under warranty. Two were found to have manufacturing defects. The rest failed because of problems such as too little oil in the system, air in the system, contaminants in the system or "installer error." The latter category included using the wrong type of compressor lubricant, not using enough lubricant, using non-approved flushes to "clean" system parts and using cross-contaminated refrigerants. Debris left over from a previous compressor failure was often the cause of the repeat compressor failure.
On GM Harrison compressors (DA6, HR6, HD6 and HT6), body seal leaks can be caused by mis-mounting the unit or not tightening the bolts properly. On these compressors, six bolts that pass all the way through from the front nose plate to the rear head plate hold the housing together. There are no dowel pins to hold the parts in proper alignment, so care must be used to prevent the housing from twisting when it is being installed. The technician must make sure the mounting brackets are not bent. The compressor should rest in the bracket with even contact at each mounting location. The bolts can then be torqued down evenly to prevent the housing from twisting.
A great deal of emphasis was put on using the OEM recommended type of lubricant for specific compressors. This is especially important with rotary vane and scroll type compressors.
Before adding fresh oil to a system, all of the old oil should first be removed. This will prevent cross-contamination of lubricants and reduce the risk of overcharging the system with too much oil (which can cause cooling problems). Always refer to the OEM oil capacity chart for the vehicle application. See the chart below.
Thermistor Vacuum Gauges
Keith Johnson of Honda spoke about the importance of thoroughly evacuating A/C systems when parts are replaced. Evacuating an A/C system with a vacuum pump pulls out air and moisture, both are contaminants that can cause problems if left inside the system. Air reduces the cooling efficiency of the system and moisture mixes with refrigerant oil to produce sludge. Moisture also can freeze and plug the expansion valve causing noise, restrictions or a complete blockage.
A pump capable of achieving high vacuum must be used to pull out all of the contaminants. When air is pulled out of the system, it creates a vacuum that causes residual moisture to boil and evaporate. For this to occur, the vacuum pump must be capable of pulling at least 29 in. Hg of vacuum throughout the evacuation process (which normally takes about 30 minutes).
Johnson said the best way to monitor the evacuation process is with a Thermistor Vacuum Gauge that reads in microns (one inch of Mercury equals 25,400 microns). It takes a highly accurate instrument to measure vacuum because even a little pressure left in the system can prevent all of the residual moisture from boiling out. Only a half-inch of mercury of pressure (12,700 microns) can reduce the boiling point of water by over 20° F. Pulling out the last fraction of an inch of pressure is the most critical step in the evacuation process to assure the complete removal of all air and moisture.
After you have pulled a deep vacuum on an A/C system, close all valves and shut off the vacuum pump. A slow rise in pressure (which you can see on the Thermistor Vacuum Gauge) will occur as the residual moisture continues to boil off inside the system. Pulling additional vacuum will get rid of this moisture. The evacuation will not be complete until the system can maintain a stable vacuum reading below 700 microns for at least three minutes.
The time it takes to completely evacuate an A/C system can be reduced by preconditioning the evaporator prior to hooking up the vacuum pump. Preconditioning raises the temperature so the moisture will boil off faster. The easiest way to raise the temperature of the evaporator is to run the engine with the heater on HOT in the RECIRC mode. Turn the blower fan to HIGH and close all doors and windows. When the engine reaches normal operating temperature, the evaporator will be thoroughly preheated and ready to evacuate.
Johnson said if you have difficulty maintaining a stable deep vacuum, there may be a leak in the A/C system, the vacuum pump or the equipment connections. Leak testing should be done prior to evacuating the system because evacuation is not always a reliable way to locate or even identify a small leak in an A/C system. Seals and O-rings that leak under pressure may move under evacuation and not leak.
Coolant Symposium
One of the highlights of the convention program was MACS’s first-ever coolant symposium. Panel members included representatives from OEM vehicle manufacturers, cooling parts suppliers and antifreeze suppliers.
The panel’s conclusion was that consumers may be neglecting proper maintenance of their engine cooling systems. Coolant system maintenance and change intervals are not being adhered to resulting in major problems for many vehicles. Shops should therefore make it a priority to take care of "cooling system management."
Engine cooling systems that contain air (from improper bleeding procedures or not maintaining the coolant level), can contribute to the breakdown of the coolant and cause corrosion and erosion inside the cooling system (which is often mistakenly thought to be caused by electrolysis). While electrolysis can be the cause of heater core failures, actual cases are rare, said panel members. Improper grounding of aftermarket electrical equipment such as sound systems can cause electrolysis.
The panel also recommended that different types of coolants (conventional green antifreeze and orange long-life antifreeze) not be mixed. The additive packages are incompatible and can reduce the coolant’s ability to inhibit corrosion.
When adding new antifreeze to a cooling system, the panel said to use a 50/50 mixture of the type of coolant specified by the vehicle manufacturer mixed with pure distilled water. The panel also recommended using a refractometer rather than a hydrometer to test the strength of the coolant because a refractometer is more accurate.
MACS News
MACS has teamed up with the EPA and SAE to produce a new consumer brochure called "Professional A/C Service and Repair" that promotes the proper servicing of automotive A/C systems by certified professionals. The new brochure has been endorsed by a number of vehicle manufacturers and aftermarket equipment suppliers. Anyone interested in obtaining a copy can call MACS at 215-631-7020 ext. 301, or email info@macsw.org.
A new toll-free Technical Helpline is now available to MACS members for technicians who need answers to A/C service-related questions. This is a member-only number, so all other questions should be directed to MACS general number 215-631-7020.
If you’re looking for A/C and cooling system repair information, you can put it on your shop computer -MACS has just released their all-new A/C-ROM. The new four-CD package covers OEM service procedures for A/C and engine cooling plus technical service bulletins for all domestic and import applications from 1983 to 2001. The CDs also include wiring diagrams, information on air bag disarm procedures, timing belt R&R procedures (with timing mark diagrams, specifications and belt interference information), cylinder head R&R procedures (for replacing head gaskets), general engine overhaul procedures, idle speed and throttle position sensor specifications and adjustment procedures, computer re-learn procedures, ECM/PROM update information, general cooling system service information, and coolant type and capacity specifications. The A/C-ROM package requires Windows 95 or higher and sells for $445 (MACS members) or $495 (non-members). A demo can be viewed at www.macsw.org.
Other CDs now available from MACS include two interactive training CDs, one on Refrigeration/ HVAC/Electrical and another on Electronics/Automatic Temperature Control. The training CDs sell for $79.95 each. Demos are also available online. MACS also has compiled all of their retrofit information including OEM TSBs on retrofit procedures on a CD for $39.95 (members) or $49.95 (non-members).
MACS’s latest coolant survey of its members shows that one out of five shops (20.5%) now recycle engine coolant on site. Nearly 18% of the shops also indicated they purchase recycled coolant for use in their customers’ vehicles.
As for the type of coolant used, 36.4% indicated they use the same type of coolant (ethylene glycol with a conventional additive package) in every vehicle they service while 63.9% said they use the specified "factory brand" type of coolant in their customers’ vehicles.
The MACS survey also found that most water pump failures (66.7%) occur between 50,000 and 99,000 miles - which is no big surprise. Only 11.1% of water pump failures occurred at 49,000 miles or less, while 22.2% occurred over 100,000 miles. The survey also found that most shops (71.5%) were installing new aftermarket water pumps or new OEM water pumps (60.7%).
As for radiator failures, the survey reported that most copper/brass radiator failures occurred between 50,000 and 99,000 miles (62.2%), while most aluminum radiator failures occurred over 100,000 miles (48.9%). Very few radiator failures were reported under 49,000 miles (4.4% for copper/brass and 8% for aluminum).
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The following is a list of recommended lubricants for R-134a compressor applications: |
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Behr/Bosch rotary compressors - Ester 100 |
Matsushita (all) - Ester 100 Mitsubishi FX80 - PAG 100 Mitsubishi FX105 - PAG 46 Nihon (all) - Ester 100 Nippondenso 6P, 10P, 10PA, 10P08E - PAG 46 Nippondenso SP127, SP134 & 6E171 - PAG 46 Nippondenso TV series - PAG 125 Panasonic (all) - PAG 46 Sanden SD500 & SD700 - PAG 100 Sanden SD710, SDB, TV & TRS - PAG 46 Seik-Seiki (all) - Ester 100 York/Tecumseh - PAG 46 |
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