How to Prepare Your HVAC System for a West Michigan Winter

There's a morning in late September when the house is fifty-eight degrees at six a.m. and somebody finally gives in and pushes the thermostat over to heat. Then comes the smell of dust cooking off, the basement makes a noise nobody remembers it making, and the whole household stands around the hall register waiting to feel warm air.

That morning is coming. The useful thing is that you get to pick when it happens.

So: a short list you can knock out on a Saturday, a test worth running on purpose instead of by accident, and the few things that need somebody with instruments. None of it's complicated. All of it is easier in September than it is in January.

Run It On Purpose, While It's Still Mild

Do this first. If you only do one thing off this page, do this one.

Pick a cool morning, set the thermostat to heat, and push the target about five degrees above whatever the room reads. Then stay down there and watch it go through three or four complete cycles — light, run, satisfy, shut off, sit a few minutes, do it again.

What you want to see is boring. The inducer fan spins up, the igniter glows, the burners catch with a soft whoomp and stay lit, and thirty or forty seconds later the blower joins in and pushes warm air. It runs for a stretch, shuts down in order, and the blower coasts to a stop.

What you're listening for is anything that isn't that. Burners that light and go out a few seconds later. A furnace that starts, tries three times, and locks itself out. A blower that comes on immediately with cold air. Grinding, squealing, or a rhythmic scraping. A furnace that runs four minutes, shuts off, and fires right back up — short cycling is its own conversation.

Finding any of that in September is good news. It means you have a week to sort it out while it's fifty-five degrees outside and we have open slots. Finding it in January means you're calling the emergency line with a cold house and a full schedule ahead of you.

A note on the smell: burning dust on the first run is normal and it fades in fifteen or twenty minutes. A sharp electrical smell, or anything like hot metal that doesn't fade, is not — we wrote up what that smell usually means separately.

The Filter Nobody Changed in August

Pull your filter out and hold it up to a light. If you can't see light through it, it hasn't been doing its job for a while.

Filters load up faster in late summer than people expect. The AC has been running hard, ragweed has been in the air since mid-August, and windows have been open on the nice days. The filters I pull in September are usually a lot worse than the ones I pull in February.

A restricted filter matters more on the heat side than the cooling side. The blower has to pull air through it, and if it can't, the heat exchanger runs hotter than it was designed to. The high-limit switch does its job and shuts the burners down, the blower keeps running, and now your furnace is blowing cool air and cycling on and off for a reason that cost four dollars to prevent.

Write the date on the cardboard edge in marker. It's the only way anybody remembers, and it settles the argument next time. If you're unsure how often yours needs it, that depends on thickness and type more than anything — we broke it down by filter type here.

Outside: Twenty Minutes, Mostly Walking

The vent pipes. If your furnace is a high-efficiency model, it exhausts through two white PVC pipes out a sidewall instead of up a chimney. Go find them. Clear anything growing in front of them, knock down any wasp nest, and look inside the openings for a bird's nest — I find those more often than you'd guess. These pipes need to stay clear all winter, which means after a heavy lake-effect dump you walk out and make sure they're not buried in a drift or under what came off the roof. A blocked intake shuts the furnace down on purpose, and that particular no-heat call always lands on the coldest weekend of the year.

The AC. Shut off the disconnect, rinse the loose stuff out of the fins, and leave it alone. Don't wrap it. A full cover traps moisture against the coil and gives mice a dry, sheltered place to spend the winter chewing on wiring. Plywood on top is fine if falling ice is a concern at your house. We went through the whole cover-it-or-don't question if you want the longer version, and the spring version of this list runs in reverse come April.

The chimney, if you have one. Older furnaces and most atmospheric water heaters vent into a masonry chimney or a B-vent, and those get blocked by nests, animals, and their own crumbling liner. You can't inspect that from the ground. Just note that you have one so somebody looks at it.

Inside: The Cheap Stuff That Adds Up

Open the registers. All of them, in every room, including the ones you closed in July because the guest room was freezing. Closing registers doesn't redirect heat where you want it. It raises static pressure in the duct system and makes the blower fight, which is worse for the equipment and doesn't fix the rooms that never feel right anyway.

Find your cold air returns and clear them. This is the one people miss. A sectional pushed flat against a return grille in the family room starves the whole system. Give it a few inches.

Look at the thermostat. Fresh batteries if it takes them. Then check that the heat and cool setpoints are far enough apart if you run it on AUTO — four degrees minimum, and I'd rather see five or six. A narrow gap in October gets you the furnace at breakfast and the AC by three in the afternoon on the same day, which isn't a malfunction, it's a settings problem.

Detectors. Carbon monoxide detector on every level including the basement, and one within earshot of the bedrooms. Then flip them over and look at the date on the back — the sensor expires in seven to ten years whether the battery is good or not, and almost nobody knows that until somebody tells them. The full CO rundown is here, and it's worth ten minutes of your evening.

Humidifier, if you've got one. New pad, and open the damper for the season. A bypass humidifier left on its summer setting does nothing all winter, and then in February people wonder why the house is so dry and the doorknobs keep shocking them.

What Actually Needs Somebody With Instruments

I'd rather be straight about the line between your half and mine.

Your half is real. Filter, test run, clear vents, open registers, working detectors. That covers most of what a homeowner can catch without tools, and if it's all you ever do you're ahead of most houses on my route.

My half needs the cover off and gauges on it. We inspect the heat exchanger with a light and a camera, because a crack doesn't announce itself — it makes heat and runs normally right up until it doesn't. We put a combustion analyzer on the burners to measure what they're actually producing instead of judging the flame by eye. We run a draft test with the exhaust fans going, which is how you catch a water heater that's spilling exhaust into the basement. We check manifold gas pressure against the data plate, clean and reseat the flame sensor, and look at amp draw on the blower motor.

That's what a furnace maintenance visit is, and I've written out everything on that checklist so you can see it isn't a mystery.

I was in a basement in Hudsonville last fall for a straight tune-up. Furnace was fine — six years old, ran clean, nothing to report. The flame sensor was a little crusty and took two minutes with a pad. But while I was standing there I noticed the condensate line had a soft belly in it where somebody had zip-tied it to a joist, and the trap was half full of the gray sludge those things grow. Another month of that and it backs up, the pressure switch opens, and the furnace quits on a night when it matters. Nobody would have caught that from upstairs.

That's why I'd rather come in the fall. Not because a tune-up is magic. Because it's the one time a year somebody looks at the parts of your house that never speak up.

If It's an Old Furnace, Decide Now

One more thing, while there's still time to do something about it.

If your furnace is past eighteen or twenty years, if you've already put real money into it, if it's been showing the signs — make the call in September, not in a cold house in December. Installation scheduling is open right now. In January it isn't, and a furnace you pick in a panic is usually the wrong furnace at the wrong price.

I'm not telling you to replace it. Plenty of twenty-year-old furnaces have another season or two in them, and I'll tell you that when I see it. I'm telling you that September is when you have leverage and December is when you don't.