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Why fall prep is different from spring prep
The spring AC checklist (see spring AC prep) is mostly about airflow, cleanliness, and efficiency. The fall checklist adds two categories the AC side doesn't have: combustion safety and cold-weather readiness. If a filter is dirty in July, you get a warm house. If a heat exchanger is cracked in December, you can get a household of people with headaches and worse.
The full combustion inspection — heat exchanger, gas pressure, flue gases with a combustion analyzer — is a technician job (see what's in a tune-up for what that includes). The six-item list below is what a homeowner can do in an afternoon before the tune-up to catch the obvious stuff and make sure the safety layers are working.
The six-step checklist
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Step 1 — Test-fire the furnace
Pick a cool morning (below 65°F outside is easier). Set the thermostat to HEAT and raise the setpoint 5°F above the current room temperature. Listen for the sequence: draft inducer starts (a low whooshing sound, 30-45 seconds), gas ignition (a soft whoosh or click, 3-5 seconds after that), then the blower kicks in about 30-45 seconds later. Warm air should reach the supply vents within 2 minutes. Anything unexpected — an ignition delay longer than 5 seconds, a bang at ignition, the blower not coming on, a burning smell that doesn't clear after 15 minutes of running — call before you rely on it.
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Step 2 — Change the filter
Same drill as spring. Fresh MERV 8 or MERV 11 in a standard 1-inch slot. In heating season a dirty filter causes short-cycling on the high-limit switch — the furnace kicks on, air can't move, temperature spikes, high-limit trips, blower keeps running until temperature drops, cycle repeats. Uncomfortable and hard on the equipment.
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Step 3 — Test every CO detector in the house
Press-and-hold the test button on every detector. Replace batteries in any that don't chirp. Note the manufacture date on the back — CO detectors have a 7-10 year service life and the sensors degrade even in units that still "test" successfully. Any detector older than that should be replaced regardless of whether the test button works. If you don't have a detector on every level of the home and outside each sleeping area, add them now, before heat season starts.
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Step 4 — Walk supply and return vents
The rooms you actually heated last winter — bedrooms in particular — should have supply registers open and return grilles unblocked. Furniture shifts, kids stash toys, area rugs migrate. Walk the house and check. Also check that any winter-specific room configurations (guest bedroom that's only used at Thanksgiving, basement family room that only sees Christmas) are set up for airflow before you actually need them.
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Step 5 — Check outdoor exhaust vents (high-efficiency furnaces)
If you have a high-efficiency (90%+ AFUE) furnace, it vents combustion gases out through PVC pipe(s) that exit the exterior wall — usually near the ground on the side of the house. Check the termination for: leaf/mulch buildup around it, snow-drift path from a roofline above, spider webs or nests in the pipe opening, physical damage from lawn equipment or wildlife. Blocked exhaust is one of the fastest ways to shut down a modern furnace on lockout (or, worse, run it with restricted venting).
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Step 6 — Book your fall tune-up
Before Thanksgiving. The heat exchanger inspection is a safety item, not an efficiency item — it's the reason we recommend the fall tune-up over just relying on the spring one. Once cold weather hits and the no-heat calls start, non-emergency tune-ups get pushed. October and early November are the calm window.
Gas safety — the two symptoms that get an immediate stop
The one symptom that doesn't get an immediate stop but should get a same-week service call: a musty or slightly burnt smell the first time the furnace runs each fall. Some of that is dust burning off the heat exchanger from months of sitting idle and clears in 15-30 minutes of running. If the smell persists past the first hour of runtime, or comes back on subsequent cycles, that's a real fault and needs to be looked at.
Van Buren timing: work backward from November
Local timing again. In Van Buren, Fort Smith, and up the River Valley into Alma and Mulberry, typical fall/winter milestones look like:
| Milestone | Typical timing | What to have done by then |
|---|---|---|
| First 60°F morning | Late September | Test-fire the furnace, filter swap |
| First frost | Late October | CO detectors tested, vents walked |
| First hard freeze (below 30°F overnight) | Early November | Professional tune-up complete |
| First sustained cold week | Mid-December | Everything above already done |
| Coldest stretch (single-digit lows) | Mid-January | Have a backup plan for extended outage |
The tune-up target of "before Thanksgiving" is not arbitrary — it's the last stretch of the calendar where you can get scheduled comfortably. Once the first below-freezing overnight hits and phones start ringing with no-heat calls, everything else gets pushed.
When to stop and call, not run through the checklist
Most of the six items above are safe homeowner work. A few situations mean skip the checklist and get us out there first:
Any smell of gas, anywhere in the house
See the warning above. 911 and gas utility first, us second, no exceptions.
The furnace didn't run at all last spring/summer, and it's more than 15 years old
An older unit that's been sitting deserves a technician's eyes before it's asked to run through a winter. Combustion equipment doesn't age gracefully in storage.
A CO detector went off at any point since the last heating season
Even if the detector reset and no one felt sick, the furnace needs a combustion analysis before it runs again for a full season. Don't wait for the detector to speak up a second time.
You see visible soot around the furnace, or rust flakes falling from the flue
Both are signs that combustion or venting was compromised at some point. Neither is safe to run through until it's diagnosed.
The furnace is a standing-pilot unit older than about 25 years
Old furnaces still work — until they don't. Once a heat exchanger cracks on a 25+ year unit, it's usually a replace-not-repair decision. Get it looked at ahead of the season, not during it.
Keep reading
For the full breakdown of what a professional fall tune-up actually measures (and why the heat exchanger inspection is the item that matters most), see what's in a tune-up. For the equivalent homeowner list on the cooling side, see the spring AC prep checklist. And if you'd rather have us handle both tune-ups automatically each year, look at our maintenance plans — bundling the fall visit with priority service in a cold snap is worth the price for most Van Buren households.
Frequently asked
My furnace runs fine — why do I need a fall tune-up? +
Because "runs fine" isn't the same as "is safe." A cracked heat exchanger doesn't stop the furnace from running; it just lets combustion gases into the airstream. A slow gas leak at a manifold union doesn't stop the burner from lighting; it just accumulates in the utility room. The fall tune-up exists specifically to catch the things that homeowners can't see or feel until they're a problem. A running furnace is the minimum bar, not proof of safety.
How often should I replace CO detectors? +
Every 7-10 years, regardless of whether the test button still works. The sensor inside a CO detector degrades with age and the test button only checks the alarm circuit — not the sensor's ability to actually detect CO. Look on the back of the unit for a manufacture date. If it's older than that window, replace the whole detector. If your smoke alarms are the combination smoke/CO type, the same rule applies (and both technologies degrade around the same rate).
Is the burning smell when I first turn on the furnace something to worry about? +
Usually not, if it clears. Dust settles on the heat exchanger over months of the furnace sitting idle, and burns off in the first 15-30 minutes of runtime the first time each fall. That produces a mild dusty/burnt smell that fades. If the smell is strong, if it doesn't clear, if it comes back on subsequent cycles, or if it smells like chemicals rather than dust, that's a real fault and needs a technician.
Do I need to do anything to a heat pump before winter (vs. a furnace)? +
Same filter swap and vent walk. A heat pump doesn't have a combustion side so no gas-safety items, but heat pumps do run outdoor defrost cycles in cold weather — verify a 2-foot clear radius around the outdoor unit, same as the summer prep. If you use electric-strip backup heat, the fall visit is a good time to have us verify the strips are actually cycling on when they should — a failed backup element in January is a cold living room.
I don't have a gas furnace — do I need a fall tune-up? +
Yes, though the visit looks different. Heat pumps and electric-strip furnaces have their own set of checks: reversing valve function, defrost board test, electric-heat element continuity and amp draw, blower and control-board voltages. No combustion analyzer, but still an hour of measurement and adjustment worth doing before the equipment is asked to run through a cold snap.