A/C System Flushing

Fig. 10 Refrigerant flushing information chart:

Several refrigerants may be used to flush badly contaminated systems, Fig. 10. For a refrigerant to effectively wash the inside surfaces of components, it must be in liquid state, as vapor will not flush away contaminants. R-12 and F-114 are best suited for flushing without special flushing equipment, as they have greater pressure at ambient temperatures and are the least toxic. However, at higher ambient temperatures, they tend to vaporize and no longer act as proper flushing agents. F-11 and F-113 are better suited for continuous circulation flushing equipment.
After components or system have been cleaned, the excess refrigerant must be cleaned out with R-12 or nitrogen. When nitrogen is used, a pressure regulator must be used on the supply tank, as high pressure can cause damage.
Clean system components as follows:
1. Discharge refrigerant system.
2. Remove compressor for service or replacement. If compressor is cleaned or serviced, add specified amount of refrigerant oil to compressor prior to installation. New compressors contain correct amount of refrigerant oil.
3. Replace orifice tube in evaporator inlet tube using suitable tool.
4. Back flush condenser and liquid line as follows:
a. Install Motorcraft adapter tool YT-1123 or equivalent on condenser liquid line tube fitting location.
b. Remove O-ring from condenser inlet tube (discharge line).
c. Clamp section of heater hose to condenser inlet tube fitting. Insert other end of hose into shop exhaust.
d. Using at least 1 lb. of R-12, backflush liquid line and condenser.
e. Remove adapter tool from liquid line.
f. Remove heater hose and clamp from condenser inlet tube.
5. Install condenser and liquid line in vehicle using new O-rings lubricated with clean refrigerant oil. Torque connection to 10-15 ft. lbs.
6. Connect all refrigerant lines. All connections should be clean and new O-rings lubricated with clean refrigerant oil. Tighten all connections with back-up wrench to avoid component damage.
7. Charge system with 1 lb. of R-12. Do not evacuate system until after leak test.
8. Using either electronic or flame-type leak detector, check all connections and components. Service any leaks located.
9. Purge system to remove air and moisture vapor.
10. Evacuate and charge system with R-12.
11. Performance test system.