Flushing Automotive Air Conditioning Systems

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First and foremost you must not leave "any" flushing solvent in the system!

Flushing is the best way to get old oil and any solid contaminants out of the components of an automotive air conditioner. My experience is from running an auto air conditioning and radiator shop that was opened in 1973. We have been flushing A/C systems sense 1973 when they are dirty or when we change compressors. Flushing is the only way to really get the majority of oil, debris and contamination out of the system. In the past 25 years we have used R-11, mineral spirits and currently have tried HFCF-141b to flush auto A/C systems. The solvent used to flush is of major concern, see below.
Flushing does present some hazards, this may be why the OEM manufacturers do not recommend flushing. Read the safety data sheet for the flushing agent you are going to use. Understand what the solvent will do to your eyes, skin and the paint of the vehicle. Flush in a well ventilated area, even non hazardous fumes displace oxygen. Take precautions to control and contain the solvent being blown through the components. Wear safety goggles and gloves as needed.
The R-11 worked fine but the vapors gave me some problems. We always flushed with the vehicle in a well ventilated area (shop doors open). It contains CFC so it's not currently in use.
Mineral spirits is not approved or recommended by OEM or after market manufacturers. Using mineral spirits may void the component Warranty. Mineral spirits are flammable. Mineral sprits are slow to evaporate so some may be left in the system. Residual flush solvent can contaminate and damage an air conditioning system! I can not recommend using mineral spirits because of these problems but it is a flushing solvent I have used for years. My shop has used mineral spirits to flush A/C systems for over 20 years with no problems or come backs that I could identify. I have used mineral spirits to clean auto parts by hand since 1960, and consider it a realatively safe product and a good cleaner. It dries the skin if used a long time but have not had any skin problems other than drying and consider It can be purchased from any paint supplier and at a reasonable price. If OEM manufacturers say that mineral oil left it the system after retrofit is OK, what harm could a small trace of mineral sprits do? It is my understanding that mineral spirits are from the same base as mineral oil. When we install a compressor we want it in a clean system with fresh oil and we do not expect it to come back with any problems! We only flush through heat exchangers and free flowing hoses. We always POP the component dry. We clean components as expansions valves which are off the car with mineral spirits and then blow them dry. Do not flush through compressors, driers/accumulators, any type of refrigerant control valves or other items that would trap the solvent! We also flush all A/C components that we repair. Mineral spirits cost about $2.00 per gallon. See procedures for flushing A/C systems below.
The new HFCF-141b (Dura 141) is recommended by most after market A/C part suppliers as Everco, Murray and Four Seasons. Dura 141 is safe and nonflammable, in fact it is also used to flush electronic components. It is the flush intended to replace CFC based flushing solvents R11 & R113 but has one tenth the ozone depleation potential. Do not flush through compressors, driers/accumulators, any type of refrigerant control valves or other items that would trap the solvent! When flushing before a retrofit it is not generaly recommended that you flush non barrier hoses. This is because the mineral in side the hose act to help seal in the R134a refrigerant. Flushing with higher pressures may not provide enough liquid contact between the sovlent and components. Murray recommends flushing at about 60PSI with dry air. See procedures for flushing A/C systems below. Four Seasons, Everco and Murray promote and sell this solvent. It cost about $70.00 per gallon.
I just received a retrofit kit that contains an ester based solvent for flushing. The kit that I bought was produced by FJC, Inc., 101 Commercial Drive, Mooresville, NC 28115. This flushing solvent is very oily, I would discribe it as thined down ester oil. Ester oil is the oil that I reccomend use when you retrofit to R-134a. FJC promotes it as 100% environmentally safe and biodegradable. I have not tried it yet but am open to any information from end users.
We use a plastic bottle to put the solvent into the system then we blow it through with a rubber tip blow gun. We only flush through heat exchangers and free flowing hoses. We use dry air or nitrogen at about 125 PSI to blow through the system. We flush in a reverse direction to refrigerant flow first to dislodge any material caught inside. After we flush the system to our satisfaction, we pop the components dry in both directions.
    Pop the components dry, means that:
  1. We blow the major part of the solvent through the component and catch it in a capture tank or shop rags.
  2. We hold the blow gun tight at one end of the component.
  3. We hold our finger over the other end until it builds up pressure.
  4. We release our finger letting it blow off pressure.
  5. We repeat until there is no sign of solvent coming out.
  6. When we flush we pull a long vacuum.
The other method of flushing that is recommended is to use refrigerant in a closed loop. This is not really flushing and does not get contaminants out of the system. It attempts to flow refrigerant through the entire system. If the system already has a blockage or contaminants in it, this method is useless. It only removes some oil. It requires the use of clean refrigerant.
(The big three in after market A/C parts)
  1. They all recommend you use R12 as long as you can get it and not retrofit until you have to.
  2. They supply and recommend a solvent for flushing air conditioning systems. It contains HFCF-141b that is a non-hazardous and non-regulated solvent for automotive use.
  3. They supply and recommend Ester oil for use when you do retrofits. Also since it is compatible with all R12/R134a compressors it could be used in a R12 system that may be retrofitted later.
  4. They recommend that you use the same oil that's already in the system when you are just adding oil. In a system that contains PAG oil you should add PAG oil.
Four Seasons Everco and Murray have hot lines that can provide you with their views and recommendations.
Four Seasons Hot Line 1-800-433-7508
Pn 59009 Ester Oil 100 vis.
Pn 59012 Ester Oil 150 vis.
Pn 59015 Ester Oil 68 vis.
Pn 59030 Flushing Solvent 141b
Pn 59031 Capture Tank (5 gallon tank to capture solvent)
Pn 59032 Capture Hose & Fitting Kit
Four Seasons has a oil capacity and viscosity recommendations in their catalog.
Everco & Murray Hot Line 1-800-325-8886 (Choice: 2, 6)
Pn 409500 Ester Oil 100 vis.
Pn 409517 A/C Flush Solvent 141b
Pn 409920 Capture Tank (5 gallon tank to capture solvent)
Pn 409921 Capture Hose & Fitting Kit
Everco & Murray have oil capacity and viscosity recommendations in their catalog.

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