Air Conditioner Maintenance Checklist

Most summer AC breakdowns trace to two things: restricted airflow indoors and a fouled coil outdoors. Both are free to prevent.

What AC maintenance actually matters?

1. Change the filter

Restricted airflow across the evaporator coil is the leading cause of AC failure. Less air means less heat absorbed, the coil runs colder than designed, and it freezes — at which point cooling stops entirely and you risk liquid refrigerant reaching the compressor.

How often: every 1–3 months for standard 1-inch filters; 6–12 months for thick media filters. Pets, allergies, and dust shorten it.

How to check: hold it up to a light.

Higher MERV isn't automatically better — a filter too restrictive for your system reduces airflow and causes the exact problem you're trying to avoid. See HVAC air filters and MERV explained.

2. Clean the outdoor condenser coil

The condenser rejects your home's heat to outdoor air. Caked with cottonwood, grass clippings, pollen, or dust, it can't — so the system runs longer, uses more energy, and runs hotter.

How to do it:

1. Cut power at the disconnect near the unit.
2. Remove leaves and debris from around and inside the unit.
3. Rinse the coil gently with a garden hose, ideally from the inside out where the top comes off.
4. Let it dry, restore power.

Never a pressure washer. It bends fins and drives debris deeper into the coil.

Once or twice a season, more in cottonwood country.

3. Keep it clear

• 18–24 inches of clearance around the unit, per manufacturer spec
• Trim vegetation — hedges grown in around a condenser are extremely common
• Don't build a decorative enclosure. The most frequent well-intentioned mistake: it restricts airflow, raises running cost, and makes noise worse. See heat pump noise levels

Also worth doing

Check the condensate drain. The evaporator coil produces a lot of water in humid weather. A clogged drain causes water damage, and on systems with a float switch it shuts the whole system down — a very common late-summer call.

Look for standing water in the drain pan. Clearing the line is usually straightforward.

Keep vents and returns unobstructed. Furniture over a return starves the system. Closing vents in unused rooms doesn't save money on most systems — it raises static pressure and reduces overall airflow.

Listen. Grinding, screeching, or repeated hard clicking without starting are worth reporting before they become failures.

Watch the bill. A steady rise with no change in use suggests declining efficiency — often a fouled coil or a developing refrigerant leak. See refrigerant leak signs.

What should an AC tune-up include?

The difference between a real service visit and an expensive filter change is numbers:

• Refrigerant pressures, compared against manufacturer specification for the conditions
• Temperature split — the difference between return and supply air, typically expected in the high teens to low twenties °F
• Static pressure, which is how duct restrictions get found
• Capacitor capacitance, measured against its rating — a weak capacitor is the most common summer failure and it's visible on a meter before it strands you
• Amp draw on the compressor and fan motors
• Contactor condition — pitted contacts are a known failure point
• Coil condition, indoor and outdoor
• Condensate drain cleared and float switch tested
• Thermostat operation

Ask for the readings. "Everything looks good" without numbers means nothing was measured.

How often does an air conditioner need servicing?

Annually, before cooling season, is the standard recommendation. For a heat pump running year-round, twice — before heating and before cooling.

Check your warranty. Many manufacturers require documented professional maintenance, and claims have been denied for missing records. Keep the invoices if yours does.

What AC services can you decline?

Routine refrigerant top-ups. Refrigerant isn't consumed. If it's low, there's a leak, and adding more without finding it is a recurring bill that also risks the compressor.

Chemical coil cleaning on a coil that isn't dirty. Ask to see it.

UV lights and air purifiers, unless you specifically want one. High-margin add-ons frequently sold as maintenance.

Duct cleaning as routine. Limited evidence of benefit absent visible contamination, mold, or rodents. Duct sealing is a different and often worthwhile job — see ductwork problems and cost.

A replacement recommendation delivered during a tune-up. Sometimes legitimate — see how long does an air conditioner last — but get a second opinion before acting on it.

Seasonal schedule

Where to go next

• AC not cooling: troubleshooting
• How long does an air conditioner last
• cost to run an air conditioner

More in our heating and cooling guides.