We’ll get to it. First, here’s the full spring AC maintenance checklist we actually work through on a Chesterfield home, and why each line matters more than you might think.

The Full Spring AC Maintenance Checklist

1. Refrigerant charge verification. Not just “is there refrigerant in the system” — a proper check measures superheat and subcooling against the manufacturer’s target for that specific unit. A system that’s off by even 10% will run longer, cost more, and strain the compressor.
2. Capacitor microfarad reading under load. Capacitors weaken before they fail. A visual “it looks fine” check catches nothing. A proper reading against the nameplate spec catches a capacitor that’s going to fail in July.
3. Condenser coil cleaning. The outdoor coil collects everything the wind blows through your backyard. Cottonwood fluff, grass clippings, pollen, dog hair. A clogged coil can cut system efficiency by 30%. Cleaning should be done with coil-safe chemical, not a garden hose blast that drives debris deeper into the fins.
4. Evaporator coil inspection. This is the indoor coil, above your furnace or inside the air handler. It gets dirty too, and a dirty evaporator is the single biggest cause of poor humidity control in a Chesterfield home in August.
5. Contactor inspection. The electrical switch at the outdoor unit that closes every time the system cycles. Pitting on the contacts is a sign it’s nearing end of life.
6. Motor amperage reads. Both the compressor and the outdoor fan motor should be pulling amps within their nameplate range. An amp draw creeping up toward the limit is an early warning of bearing failure.
7. Blower wheel inspection. The fan wheel in your furnace cabinet that pushes air through the ducts. When it gets caked with dust, the system moves less air, works harder, and wears faster.
8. Air filter change. Sounds obvious. Still worth saying: the filter should be changed, not just looked at.
9. Condensate drain line flush. The line that carries condensation away from the evaporator coil. A clog means water backs up into the pan, the float switch trips, and the system shuts off. Often mistaken for a total AC failure when it’s actually a $0 fix.
10. Thermostat accuracy check. A thermostat reading off by even two degrees changes how the system runs.
11. Temperature split verification at the supply registers. A healthy system drops air temperature by about 18-22 degrees between return and supply. Outside that range is a clue something’s off.

That’s the full checklist. And every one of those items is on basically every honest AC maintenance visit you’ll get. So what’s missing?

The Item That Never Makes the List: Ductwork

Here it is — the thing most spring maintenance visits skip and most homeowners never think about: the condition of the duct system that all this beautifully tuned cooling is traveling through.

A perfectly maintained, 18-SEER high-efficiency system can still deliver mediocre performance if the ductwork is leaking, disconnected at a plenum joint, crushed behind drywall, insufficiently insulated through an attic, or clogged with 30 years of accumulated debris. On a Chesterfield home — especially one built in the 80s and 90s when duct sealing wasn’t rigorously enforced — it’s not unusual to find 15-25% of the cooled air leaking out into unconditioned attic space or basement cavities before it ever reaches the rooms you’re actually trying to cool.

You paid for all that air. Your compressor ran the cycles to produce it. And a meaningful chunk of it is dumping into a crawl space where nobody lives.

A real AC maintenance visit in a 20-year-old Chesterfield home ought to include at minimum a walk through accessible duct runs — basement, crawl space, attic — looking for obvious leaks, disconnected joints, and crushed sections. If anything looks off, the next step is a proper duct assessment: sometimes a pressure test with a blower door, sometimes just a thorough visual with a flashlight and a smoke pencil.

“Austin has been maintaining my heat and AC unit for the past couple years. Always respectful and always on time.”
— Eric W., AAA Heating & Cooling customer

Why Chesterfield Homes Are Particularly Prone to Duct Issues

A big slice of the Chesterfield housing stock was built between the late 1970s and mid-1990s, before the tighter energy code revisions that made properly sealed duct systems standard. Metal trunks and flex-duct branches were commonly installed with tape that dries out and falls off after 15-20 years. Registers in rooms above the garage or over unheated spaces often share duct runs that were never insulated adequately for the kind of deltas we see in a Missouri summer.

If your upstairs bedrooms never quite cool down, if one room is always 5 degrees off the thermostat setting, or if your utility bills are higher than neighbors’ with comparable homes — the duct system is almost always involved. Fixing the ducts is often a bigger comfort and efficiency win than replacing the AC unit itself.

While you’re thinking about what’s moving through those ducts, it’s also worth considering professional air duct cleaning. Decades of drywall dust, pet dander, pollen, and construction debris accumulate inside the ductwork in ways that affect both system performance and the air you breathe. A proper cleaning pairs well with a spring tune-up.

Don’t Skip the Indoor Air Quality Conversation Either

The other Chesterfield topic that usually doesn’t come up on a standard maintenance visit — but should — is indoor air quality. Whole-home humidifiers, air scrubbers, and higher-MERV filtration setups all interact with your AC’s performance, and a technician walking through your home in April has a better view than anyone into how your whole system is working together.

“I’ve used AAA Heating & Cooling for several years and have always been pleased with their service. Austin was out last week for annual HVAC maintenance.”
— Terri K., AAA Heating & Cooling customer

Schedule Your Chesterfield Spring AC Service

Whether you want the full maintenance checklist run top-to-bottom, a second opinion on what another company found, or just an honest duct walkthrough to see where the losses are, our Chesterfield service team is booking spring appointments now. Call AAA Heating & Cooling at (636) 397-3200 to schedule. Our Service Club Members get priority scheduling and a standing discount on repairs if anything turns up. For more reading, here’s the full HVAC maintenance checklist and our deeper AC unit maintenance guide. You can always head to our main AC service page to see everything we cover.