Cleaning a condensing unit can be an important part of maintaining the longevity of your condensing unit. Should you use a pressure washer or liquid cleaner though? The short answer is NO! Do not use a power washer. You may damage fins or other parts of the condensing unit. Use a garden hose and spray into the coil to remove all the dust and other stuff that gets onto the coil over the season. As for liquid cleaners, most of them contain corrosive agents and you don’t want to damage the coil or any other parts of the unit with which it comes in contact.
If you're thinking about cleaning a condensing unit, a certified AC repair contractor will have specialized cleaners in cases where the coil needs to be thoroughly cleaned.