Oil, sludge and debris that is left in the system can clog the condenser, orifice tube or expansion valve and damage the compressor. Flushing can remove excess oil and debris from previous services. You do not want to add yet another charge of oil while leaving an unknown amounts of oil in the system.
Caution!
Only flush a condenser that capable of being flushed. The answer to question #14 deals with this problem in greater detail.
