AC Maintenance Checklist: What to Do Yourself and What to Leave to a Pro

Do these six things yourself with no tools and no risk — filter, clearance around the outdoor unit, condensate outlet, registers and returns, thermostat batteries, and a test run before the first hot week. Do three more yourself only with the power off at both the breaker and the outdoor disconnect. Leave six to a licensed technician, because they involve line voltage, refrigerant, a sealed cabinet or a combustion appliance. Everything below is sorted into those three tiers, with the consequence of skipping each item stated plainly.

How to use this list

Three tiers, not one list

A maintenance checklist is only useful if it tells you who should be doing each item. Tier 1 is anything you can do with the system running and nothing sharper than a marker in your hand. Tier 2 is work that puts you near the equipment, so it starts with two power-off actions and does not begin until both are done. Tier 3 is work that requires training, instruments and certification, and putting Tier 3 items on a homeowner list is how people get hurt.

What “annual” really means

The Tier 3 items are what a professional visit is for, and once a year for a central AC and twice for a heat pump is the standard cadence. That interval is a convention rather than a proven optimum, and the argument for it — including the warranty terms that make it enforceable — is set out at how often you should service your AC. This page does not re-argue it. It tells you what is on the list.

Print or save the one-page version

The three tiers below are deliberately short enough to print. Tape the sheet inside a utility cupboard with your filter sizes written on it, and the whole system becomes a five-minute annual habit instead of a thing you mean to get to.

Tier 1 — do these yourself, no tools, no risk

1. Replace the filter and write the date on it. The single highest-return maintenance action available to a homeowner: the Department of Energy attributes a 5–15% reduction in an air conditioner’s energy consumption to routinely replacing or cleaning air filters. Finding the slot, the size, the airflow arrow and the right MERV rating is a job of its own — see how to change your AC filter.
2. Clear two feet around the outdoor unit. Walk the perimeter and move anything stored against it, cut back shrubs, and rake out leaves. If this means putting your hands on or into the cabinet rather than just tidying the space around it, it is a Tier 2 job — see below.
3. Check the condensate outlet is running. On a humid day with the system running, find the drain outlet (usually a PVC pipe ending outside near the equipment or the outdoor unit) and confirm water is dripping from it. Nothing coming out on a day the system is working hard is an early warning.
4. Open the registers and clear the returns. Every supply register open, no furniture over a return, no rug across a floor return. Closing vents in unused rooms does not save money; it raises duct static pressure and starves the system of air.
5. Change the thermostat batteries. Once a year, before the season, whether or not it is complaining. A dead thermostat is the most common “my AC is broken” call that is not an AC problem.
6. Test the system before the first hot week. Run cooling for fifteen minutes on a mild day in spring. You want to find a fault in April, at business-hours rates, not in July at emergency rates.

Tier 2 — do these yourself with the power off

1. Rinse the outdoor condenser coil. With power confirmed off at both the breaker and the outdoor disconnect: brush loose fluff off dry, then rinse the fins with an ordinary garden hose. Three non-negotiables — garden hose only, never a pressure washer (pressurised water folds the thin aluminium fins flat, permanently); rinse from the inside of the cabinet outward so debris is pushed back the way it came in rather than packed deeper into the coil; and no bleach and no mixing of cleaners. If a rinse is not enough, a foaming cleaner made for condenser coils, used with gloves and eye protection, is the correct product.
2. Flush the condensate drain line. With power off at the breaker serving the air handler or furnace, and at the outdoor disconnect too if you will be near the outdoor unit — clear the drain. Use vinegar or a diluted bleach solution, never both. Mixing bleach with vinegar or any acid releases chlorine gas, and condensate lines run through closets, attics and crawl spaces with very little air movement, which is exactly where a gas like that becomes dangerous. Wear gloves, and wear an N95 respirator if the pan is slimy or visibly mouldy — EPA’s mould guidance covers when a cleanup is beyond a homeowner. Full method at clearing a clogged AC drain line.
3. Clear vegetation and check the pad is level. With power off at both the breaker and the outdoor disconnect, cut back growth to two feet on every side and look at the pad the unit sits on. A pad that has sunk on one corner puts strain on the refrigerant line set and can affect oil return in the compressor. Note it and mention it at the next service visit; re-levelling a unit is not a homeowner job once the lines are connected.

Tier 3 — leave these to a licensed pro

1. Anything inside the electrical compartment. Capacitors, contactors, wiring, boards. Stored charge, line voltage, and no homeowner-safe test method.
2. Refrigerant charge, superheat and subcooling. This is the item that separates a real visit from a look. Pressure readings alone never confirm a charge — a technician verifies it by measuring superheat on a fixed-orifice system or subcooling on a system with a TXV, using line temperatures alongside the gauges. Refrigerant handling is also certified-technician work under EPA rules, and homeowners cannot legally buy most refrigerants.
3. Evaporator coil cleaning. The indoor coil sits sealed inside the air handler or furnace plenum, and reaching it means opening and correctly re-sealing that cabinet. It is a different and more expensive job than rinsing the outdoor coil, and it is not a Tier 2 task no matter how a list presents it.
4. Blower and motor service. Cleaning a blower wheel means pulling the assembly. A wheel caked with dust moves dramatically less air, and an unbalanced one after a bad reinstall will destroy its own bearings.
5. Electrical connections and amp draw. Tightening lugs and measuring running current against the nameplate rating is how a failing compressor or a weak capacitor is caught before it strands you. It requires a meter and live-equipment training.
6. Combustion and heat-exchanger inspection on a gas furnace. If your indoor equipment is a gas furnace, this belongs on the annual list and it belongs to a professional. See the safety note immediately below.

What actually goes wrong if you skip each one

Not every skipped item costs the same, and knowing the failure mode lets you decide what actually matters in a busy year.

For what the Tier 3 list costs as a paid visit, contractor cost guides put a single professional tune-up at roughly $70–$200 — the breakdown, and what should be on the invoice, is at AC tune-up cost. If ice is what brought you here, deal with that first at frozen AC coil.

What your warranty requires you to document

Manufacturers commonly condition the parts warranty on documented professional maintenance, so the records are part of the maintenance, not an afterthought. Keep these four things together in one folder — paper or digital, it does not matter, as long as it survives a house move:

• The registration confirmation for the equipment, with its model and serial numbers.
• Every service invoice, dated, showing the work performed and the contractor’s licence number.
• The installation paperwork, including any permit and, in California, Title 24 and HERS documentation.
• Your own filter log — dates and sizes. It is not usually required, but it costs nothing and it answers a question that gets asked.

Read your own warranty document rather than a summary of it, including this one. The terms that govern your claim are the ones in your paperwork.

The seasonal rhythm: what to do when

FAQ