Like most preventive maintenance routines, the idea behind AC flushing is sound in theory. However, in practice, it's often done with equipment that hasn’t been properly maintained. If the flushing machine is contaminated, it can introduce debris into an otherwise clean system—doing more harm than good. This is why some people would rather not take the risk. You never know how often workshops maintain their equipment.

Also, if the system is already dirty, that’s a red flag. The A/C system is sealed, so contamination usually points to a deeper issue, such as compressor failure. It's worth considering: you don’t routinely change the oil in your refrigerator or home air conditioner, because those systems remain sealed and clean under normal conditions.