Imagine eating roasted yam with red oil and washing the plate with only very clean water and no soap.
Imagine washing a white shirt with good soap but in dirty gutter water.
These two scenarios is often what plays out in our car AC systems when it goes bad.
When a car AC system packs up it more often than not does so with contaminants in it. It's very noticeable to the eye when its said to have black oil or has virus. Car AC operates best when the system is very clean. To achieve this most AC technicians use soapy water, petrol, thinner, ethanol, alcohol, battery water, cooking gas, acetone etc to flush the system. This sometimes works temporarily then packs up leading to even more expensive return repair. Why? Because they used a wrong flushing solvent that did not dissolve and flush out all polar and non polar impurities in the AC system completely. The residue left in the system will slowly and surely grind the compressor, block the condenser/ expansion valve and tear out rubber components. Insist on using the right flushing solvent before vacuuming and gasing. BETHEL AC FLUSH SOLVENT is what I have used, seen some AC technicians use and for once witnessed product reliability in that area. It's cleans the car AC system thoroughly, evaporates very fast, does not degrade rubber or aluminium components and leaves no residue. It's available in Ladipo, trade fair and other car parts market.