It is appalling the number of systems we come across in our time in the field where compressors have been replaced, sometimes more than 3-4 times and the system has never been flushed! Can you imagine not only the filings and contamination, but the sheer glut of oil in the system.
Flushing is necessary to ensure that the system is clean and free of contamination to operate efficiently!
As one of our customers said (he must have been doing some painting in the holidays!) :
“ flushing a system is like putting an undercoat on!”
Remember that the TX valves (Thermostatic Expansion Valve) has a tiny orifice and almost sprays the liquid into the evaporator, so that the cooling effect takes place. (think of an aerosol can – and you have the idea) Any filing from a compressor failure can either block the TX valve or harm its operation. Obviously, it is ideal when replacing a compressor to replace a TX valve and we should be reminded that manufacturers such as Sanden and Denso insist on this being done every time that a compressor is replaced. Never back flush a TX Valve .
Evaporator coils are also critical to be flushed. Imagine a compressor failure and it pumps filings through the system and blocks the valve. As the compressor is failing any filings build up in the filter drier the compressor pumps until the AC system is cut off. The vacuum that is pulled in the suction side of the system means that all filings and oil in the compressor are sucked straight into the Evaporator coil! The result – and evaporator coil full of filings.
Condensers get the heat out of the system and lead to making that cool air blow out the vents. Remember any Modine or tube and fin condensers can be flushed but Parallel flow condensers like seen on most current vehicles can not be flushed and need replacing. The flush will simply take the easiest route and may miss many tubes leaving a lot of foreign material in the system.
Flushing is a good practice for any system not performing even if not replacing a compressor. When you don’t know the history of a system, you may have had a compressor replaced by another tech and not have a clean system. Over time an oil ‘sludge’ builds up and hinders cooling. A system additive, Hi-Cool helps to overcome this and has a lubricity agent in to help compressor run smoother, cooler and last longer.
Beware of oily flush solvents in the market place. These leave a residue that can affect oil viscosity and even lead to compressor failure down the track. Make sure you specify a TO-28729 flush when ordering. Try by dropping a finger in the top of the solvent and watch the oil even be dried off the end of your finger as it evaporates.
Always remember to give the system a good vacuum following with a 2 stage pump to avoid any flush being left in the system and make sure you use dry nitrogen to blow out. Any flush left will result in a hydraulic lock up in the compressor which we want to avoid at all costs!