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A/C Condensers - Flush Or Replace?

Copyright AA1Car.com
Adapted from an article written by Larry Carley for Underhood Service magazine

Should you flush or not flush a dirty condenser? When an A/C system contains sludge, compressor debris or other solid contaminants, what is the best course of action?

Unfortunately, there is no simple answer to this repair dilemma because the answer depends on the circumstances, the vehicle, the contaminants in the system and the style of the condenser.

Condensers are trash collectors. Any debris that comes out of the compressor goes straight into the condenser. It is a low spot in the system so debris and oil naturally collect in the condenser. But the debris does not stay put. Refrigerant flowing through the condenser can pick up debris and carry it to the orifice tube, expansion valve or back to the compressor. Debris can plug up the orifice tube or expansion valve, causing a blockage and loss of cooling. Such blockages also can prevent the circulation of oil in the system, starving the compressor for lubrication.

If the condenser is dirty, why not just replace it? That is what many experts recommend. But condensers are expensive to replace, especially on some newer vehicles that have a radiator/condenser cooling module. The alternative is to clean the condenser with an approved flushing chemical that hopefully will remove most or all of the contaminants. Flushing can save money, but it also increases the risk of a repeat compressor failure or an orifice tube or expansion valve blockage if the flush fails to remove all of the gunk from the condenser.

Many compressor manufacturers will not honor their warranty if a replacement compressor fails due to recontamination or improper flushing. If you flushed the condenser and failed to get it clean, or you used a cleaning product that is not approved for flushing A/C systems and the new compressor dies as a result, you risk a repeat compressor failure.

Something else to keep in mind about flushing is that it follows the path of least resistance. In a serpentine-style condenser, there is only one path the refrigerant can follow so the flushing chemical will follow the same path from the entrance to the exit. In a parallel flow condenser, the flush may not flow through all the tubes if some are partially or completely blocked. Attempting to flush a dirty parallel flow condenser, therefore, is probably a waste of time.

Some say it's also a waste of time to flush newer serpentine condensers that have the extremely small extruded tubes. The openings only measure .040" to .060" - which improves cooling efficiency but makes it very difficult to clean by flushing. Older tube-and-fin-style condensers with large tubes can be more easily cleaned with flush.

To reduce the risk of residual debris from a flushed condenser passing into the system and causing problems, an in-line filter should be installed in the liquid line after the condenser to trap any debris before it can cause trouble. A filter screen also should be installed in the suction hose at the compressor inlet to trap any junk before it can enter the compressor. Debris can be blown backward into the suction hose and evaporator by a compressor failure, too, so don't overlook this part of the system if you are flushing to get rid of contaminants.

If flushing does not remove most of the contaminants, there may be so much residual debris in the condenser that it may plug the in-line filter. If this happens, the resulting blockage will have the same effect as a plugged orifice tube or expansion valve. That you don't want.


Condenser Sludge & Black Death

Sludge is what you get when moisture gets inside an A/C system. Moisture reacts with the compressor lubricant and refrigerant and forms corrosive acids. The acids eat away at the metal parts and create sludge that can damage the compressor and plug the orifice tube or expansion valve.

Ford FX-15 compressors have had a high failure rate from "Black Death." So if you find a Ford A/C system full of black goo, Ford recommends replacing the FX-15 compressor with a new or remanufactured FS-10 compressor and installing a new accumulator, hose assembly, orifice tube and condenser. Ford does not recommend flushing the A/C system in this instance.

Corrosive acids also can eat pinholes through the evaporator and condenser from the inside out, creating refrigerant leaks. Flushing a leaky evaporator or condenser is a waste of time because the parts need to be replaced. There are sealants that can be used to temporarily plug a leaky evaporator or condenser, but some refrigerant recovery and recharging equipment suppliers do not recommend using sealants in A/C systems because the sealer may gum up the hoses and valves on service equipment.

Condenser Flushing

Only two vehicle manufacturers have recommended flushing to clean condensers: Ford and GM. Ford approves flushing with VSL338 terpene-based solvent, while GM says it is OK to flush but with liquid R-134a only in a closed-loop recycling or recharging machine to prevent loss of the refrigerant.

Chrysler and Toyota do not recommend flushing. If an A/C system is contaminated and contains debris, Chrysler says replace the condenser and hoses.

If you do flush parts, flush only the condenser, evaporator and hoses. Do not flush a compressor, accumulator, orifice tube or expansion valve. Replace the accumulator, orifice tube or expansion valve. Also, do not flush hoses that contain in-line filters or mufflers. Replace these hoses with new ones.

Various types of flushing equipment are available. For open-loop flushing with an approved solvent, the setup includes a tank, hose, gun and adapters and catch pan. The equipment uses shop air to drive a 50 psi pump for the gun. Flushing takes about 15 minutes. Afterward, the condenser and other parts must be allowed to air dry for about 45 minutes before they are returned to service.

Another type of flushing equipment uses shop air to pulse the flushing chemical through the components that are being cleaned. This helps dislodge debris and reduces the overall flushing time to 30 minutes or less. This type of power flushing equipment typically sells for $2,000 to $3,000.

Flushing also can be used to remove residual lubricating oil from an A/C system. This should be done when retrofitting older R-12 systems to R-134a to remove the mineral oil. Flushing is also recommended if an A/C system contains too much oil, dirty oil or the wrong type of oil.

Flushing Chemicals

Do NOT use any chemical except one that has been approved for flushing A/C systems. Do not use parts solvent, brake cleaner, degreaser, carburetor cleaner or similar products because they can leave behind chemical residues that may cause problems. Also, avoid any chemicals that are hazardous or toxic.

A flushing agent should have good solvent properties, be compatible with all system components (O-rings, seals, etc.), be safe and easy to use, dry quickly and leave no residue that could cause problems later on. R-11 used to be used as a flush, but is no more because of the restrictions on CFCs. Liquid R-12 or R-134a can be used to flush a system, but may not dislodge solid debris. Slow-drying ester oil-based hydrocarbon solvents also are available but typically require long flushing cycles (over an hour!), special flushing equipment and are difficult to remove (which increases the risk of oil overcharge and contamination). Some flushes also are flammable and dangerous to use.

One flushing product approved by several compressor manufacturers is HCFC-141B. This chemical is marketed under a number of brand names including "Dura Flush 141" and "Acc-U-Flush." HCFC-141B has excellent cleaning properties, evaporates quickly and leaves almost no residue in the system (less than 4 ppm). It is nonflammable, safe to use and is compatible with both R-12 and R-134a systems. This type of product can be used with an open-loop flushing system.

Ford has approved the use of a product called "Clear-Flush" by Bright Solutions Inc. This is a terpene-based cleaning solution that does an excellent job of removing contaminants. It also is compatible will all types of compressor oil and it evaporates easily.

Flushing chemicals are available from:
Bright Solutions
Cliplight Mfg.
Micro Care Corp.
Technical Chemical Company

Condenser Replacement

If you opt to replace a dirty condenser, make sure the replacement condenser has the proper cooling capacity for the application. It should have the same or higher BTU rating as the original.

If you are replacing the compressor and condenser on an older vehicle and retrofitting the system to R-134a, a larger or more efficient condenser can improve cooling performance.

Other parts that should always be replaced following a compressor failure or condenser failure include the accumulator or receiver/dryer, any A/C hose that has a muffler or in-line filter, and the orifice tube or expansion valve. Installing a variable orifice tube can improve cooling performance at low speed, especially on R-134a retrofits.

When everything is put back together, completely evacuate the system by pulling a high vacuum for 30 to 45 minutes. This is necessary to pull out all the air and any residual moisture that may be lurking in the system. Then recharge the system with the correct amount of refrigerant and the recommended type and quantity of compressor oil. Do it right and there should be no comebacks.

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