Though automotive air conditioners are closed systems, they still accumulate contaminants, mostly rancid compressor oil. Moisture in the system reacts with the oil to form sludge which creates corrosive acids that eat away at the metal passageways, causing refrigerant leaks and plugging small orifices. Most of this toxic gunk accumulates in the system's condenser. If the condenser already has pinhole leaks, the decision is made for you: Install a new condenser. If the condenser is still viable, however, there are commercial chemicals and procedures to flush the bad stuff out of the system. Most of these chemicals are used as an adjunct to professional power flushing equipment and require disassembly of air conditioning components.
Of the major auto manufacturers, only Ford and General Motors recommend flushing a contaminated condenser. Toyota and Chrysler do not endorse flushing and recommend condenser replacement, instead. No OEM or aftermarket manufacturer will honor its warranty if a cleaning product that is not approved for flushing air conditioning systems is employed and damages the compressor or other components.
The chemical flush should dissolve sludge, not damage system components like O-rings and seals, be safe to use, quick-drying and leave behind no residue. It should also meet requirements set by the U.S. Environmental Protection Agency and the Occupational Safety and Health Administration. Brake cleaner, engine degreaser and carburetor cleaner are all examples of compounds not to use to flush an air conditioning system.
The most widely accepted air conditioner flush is HFCF-141B. A hydrochlorofluorocarbon solvent marketed under a variety of names, including Dura II Flush, HFCF-141B is an efficient cleaner, evaporates quickly and leaves no residue. It is completely nonflammable and won't corrode rubber seals and O-rings.
Ford approves the use of a flush marketed under the name Clear Flush. It is a VSL338 terpene-based solvent efficient at removing oil and sludge and compatible with all types of compressors.
Chlorofluorocarbon-based solvents (CFCs) such as R-11 were used as air conditioning flushes for many years with good results. Eventually, however, R-11 was banned as being harmful to the ozone layer. Now a hydrofluorocarbon-based alternative called RX 11 has been developed by Dupont. Like HFCF-141B, another hydrofluorocarbon flush, RX 11 is EPA-approved and an effective solvent for removing sludge from air conditioning systems.
Mineral spirits are an old-fashioned and inexpensive flush solution but have a number of disadvantages in modern air conditioners. The residue is very difficult to completely remove from the system after flushing and can damage system components over time. Mineral spirits are also flammable and are a skin irritant.
