Before the cooling season, the outdoor condenser coil deserves a look. Dirt, pollen, leaves, and bent fins restrict airflow, and the system works harder to move the same heat. Some of that care is yours. Some of it is a licensed technician's. The line falls at the cabinet panels: what you can do with the cabinet closed, and what needs the panels off.
What is yours to do
Start with the power. Turn the unit off at the switch on the wall or at the outdoor disconnect, and turn off its breaker in the panel before you touch the cabinet. Keep the power off until you are finished.
Clear the area around the unit. Remove leaves, grass clippings, and stored items. Trim plants so they sit well back from the cabinet, as the installer's manual describes.
Rinse the outside of the coil gently with a garden hose, at low pressure, and let it dry before you restore power. Do not use a pressure washer. Use a coil cleaner only if the manufacturer's instructions allow it, and follow the label exactly.
What belongs to the technician
Opening or removing cabinet panels, testing or adjusting the fan motor, the capacitor, or any wiring, and checking refrigerant pressure all belong to a licensed technician. Refrigerant should never be added by a homeowner. A deep chemical cleaning or a coil with heavy buildup also belongs to the technician, as does checking the condensate drain and the airflow across the indoor coil.
Decide before you book
If the coil looks clean and the area is clear, a homeowner rinse may be all the season needs. If the coil is matted, if the unit has been running hard on hot days, or if you cannot shut the power off with confidence, book the visit. When you call, ask the following.
Does the visit include a coil cleaning, or only an inspection? Ask what the visit covers, in writing.
Will the technician note the coil condition, the airflow, and any readings on your paperwork?
Is any refrigerant or electrical work quoted separately, and is it written out before it begins?
Will the technician show you the coil condition before and after the visit?
Keep the findings with your house file. Compare the unit's age against the central air conditioner or heat pump page. The age tells you how closely to watch the season. It does not tell you what the next visit will find.