The HVAC Maintenance Checklist That Actually Matters
Most HVAC maintenance is not a mystery service. It is a short list done consistently: change the filter, keep the coils clean, keep the drain clear, and get a real inspection twice a year — once before cooling season and once before heating season. Do that and you catch small problems while they are still small and cheap. Here is the list that actually matters for a Southern Indiana home, and the clear line between what you can handle and what needs a technician.
From the field — Justin Henry, Henry Brothers · Updated July 28, 2026
Every Month or Two: Check the Filter
If you do one thing off this whole page, do this one. Changing the air filter is the single highest-return habit in HVAC maintenance, and it is the cheapest. A clogged filter starves the coil of airflow, which makes the system work harder, cool less, and eventually freeze the coil into a block of ice that blows almost no cold air at all.
Pull it every month or two and hold it up to a light. If you cannot see light through it, it is done — put in a clean one. A 1-inch filter usually needs changing every one to three months; a thick 4- or 5-inch media filter can go six months to a year. Homes with pets, shedding trees, or a lot of dust run through them faster.
MERV is just the filter’s rating — a higher number traps finer particles but chokes airflow faster, so for most homes a mid-range MERV 8 to 11 is the sweet spot between clean air and a system that can still breathe. The EPA's explanation of MERV ratings frames it the same way: go as high as your system's fan and filter slot can actually accommodate, and check with a technician before you jump a system up to a filter it cannot pull air through.
Spring: Getting Ready for Cooling Season
Spring maintenance is about the outdoor unit and the drain — the parts that do the heavy lifting once the Ohio Valley turns muggy. Work through these on a mild afternoon, well before you actually need the air conditioning.
Clear the outdoor unit
The outdoor unit dumps your home’s heat into the yard, and it needs room to breathe to do it. Over the winter it collects leaves, cottonwood fluff, grass clippings, and mulch piled up the sides. Pull all of that away and cut back any shrubs grown tight against the fins so there is a couple of feet of clearance on every side.
Rinse the coil gently
With the power off at the outdoor disconnect, rinse the fins from the inside out with a garden hose to wash the season’s grime out of the coil. Use plain water pressure — never a pressure washer, because the aluminum fins bend at almost nothing and bent fins choke airflow just like dirt does.
Check the condensate drain
As the coil pulls humidity out of the air, that water leaves through the condensate drain. In our humid summers that line grows algae and clogs, and a clogged drain backs water up into the pan and onto the floor. Find the line, make sure it runs clear, and flush it so it is ready for a summer of steady dripping.
Test it before the first hot week
Do not wait for the first 90-degree afternoon to find out the air conditioning quit over the winter. On a mild day, drop the thermostat and let the system run for fifteen or twenty minutes. The air at the vents should feel distinctly cold, and the outdoor unit should hum along without odd noises. Catch a problem in April and you fix it in no rush.
Fall: Getting Ready for Heating Season
Fall flips the list toward the indoor side and toward safety. You want the heat proven out before the first hard freeze, not discovered dead on the coldest night of the year.
Change the filter again
A fresh filter matters just as much for heating as it does for cooling — the same airflow that a furnace or heat pump needs to warm the house evenly. Start the heating season with a clean one, then keep to your every-month-or-two check right through winter.
Open and clear the registers
Walk the house and make sure supply and return registers are open and not blocked by furniture, rugs, or boxes that migrated over the summer. Closing off vents to unused rooms does not save much and often just unbalances the system and strains the blower.
Run a heat test before the first freeze
Switch the thermostat to heat on a cool day and let it run. Expect warm air within a few minutes and no burning-dust smell past the first few of them. If the heat is weak, slow, or the system short-cycles, that is far better to learn in October than during a January cold snap.
Fresh carbon monoxide alarm batteries, if you heat with gas
If you have a gas furnace, a working carbon monoxide alarm is not optional. Test it and put in fresh batteries at the start of every heating season. Gas heat is safe when the equipment is sound, but a cracked heat exchanger or a venting problem is exactly the kind of thing a good alarm catches early. The EPA's page on carbon monoxide indoors names leaking chimneys and back-drafting furnaces among the household sources, and makes the point that matters: CO is odorless and colorless, so an alarm is the only thing that will tell you.
What a Professional Tune-Up Catches That You Can’t
Your half of the list keeps the system breathing and draining. The other half needs gauges, meters, and a license. A technician measures the refrigerant charge to catch a slow leak before it starves the coil, tightens the electrical connections that loosen and arc over years of heat cycling, tests the capacitor that starts the compressor and fan (a weak one is a classic mid-summer failure), and on gas heat inspects the burners and heat exchanger for combustion and safety problems you would never see from the outside. That twice-a-year inspection is what our Clean and Check℠ visit is, and what a maintenance membership keeps on a schedule so it does not get forgotten — measuring the numbers a homeowner has no way to read, and catching the small stuff before it becomes the expensive stuff.
That is not our list — it is the industry's. Compare it to ENERGY STAR's maintenance checklist, which calls for annual pre-season check-ups — cooling in the spring, heating in the fall — and puts the same items on the technician's half: refrigerant charge, electrical connections, condensate drain, coils, and burner combustion. It also gives the number that explains why airflow keeps coming up on this page: airflow problems can cut a system's efficiency by up to 15 percent.
Mini Splits Need a Slightly Different List
Ductless mini splits share the same core list — airflow, coils, drains — but the details shift. The filters are washable plastic screens instead of throwaway cardboard: pop them out every few weeks, rinse them under the tap, let them dry, and slide them back in. No trips to the hardware store, just a habit.
The part homeowners miss is deeper in the indoor head. Behind the filters sits a spinning blower wheel with dozens of little vanes, and in a humid house that wheel grows a film of grime and, eventually, mildew. That is what turns into the musty smell and the black specks some ductless owners notice — and it is past what a rinse can reach.
Southern Indiana humidity is the reason the coil and blower on a mini split need real attention. These units run long and quiet, condensing water out of the air for hours at a stretch, and that damp, dark coil is a happy home for buildup. A deeper Clean and Check℠ on a ductless system gets into the coil and the blower wheel that a filter rinse simply cannot.
HVAC Maintenance — Common Questions
How often should HVAC be serviced?
Once a year at a minimum, and twice is better in a climate like Southern Indiana’s. The pattern is a cooling tune-up in spring and a heating tune-up in fall, plus a filter change every one to three months in between. Systems that run hard through muggy summers and freeze-thaw winters wear faster, so two visits a year keep small issues from turning into a July or January breakdown.
Can I do HVAC maintenance myself?
A good chunk of it, yes. Changing the filter, clearing leaves and clippings away from the outdoor unit, gently rinsing the outdoor coil with a hose, keeping registers open and unblocked, and flushing the condensate drain are all safe homeowner jobs. What you cannot do without gauges, training, and a license is check the refrigerant charge, test the capacitor, tighten electrical connections, or inspect a gas furnace’s combustion. That half needs a technician.
What happens if you skip HVAC maintenance?
The system keeps running, right up until it doesn’t. Dirty coils and clogged filters make it work harder for less cooling, which drives up the power bill and shortens the life of the compressor — the most expensive part on the machine. Skipped drain cleanings lead to water backing up and overflowing. Most mid-summer no-cool and mid-winter no-heat calls trace back to something a routine check would have caught months earlier.
When should I schedule a tune-up in Indiana?
Aim for the shoulder seasons — a cooling tune-up in spring before the first real heat wave, and a heating tune-up in fall before the first hard freeze. Booking in April and October means a technician finds a weak part while the weather is still mild, instead of during the first 95-degree week when the system is running flat out. It also beats the seasonal rush, when everyone calls at once.
Want the Twice-a-Year Half Handled?
You keep the filter fresh; we measure the parts you can’t. Henry Brothers does the real inspection — refrigerant, electrical, capacitor, combustion — on central air, heat pumps, and mini splits for homeowners across Clark and Floyd County. Two brothers who would rather keep a sound system running than sell you one you don’t need. No trip charge in Clark and Floyd County.