Colorado doesn't ease into winter — it drops 40 degrees overnight sometime in October and your furnace goes from idle to full duty in a day. This is the homeowner-side checklist: the 20-minute walkthrough you do yourself, the things only a tech should touch, and the order to do them in. Do this every October and you'll prevent most of the emergency calls we run in January.
On this page
Inside the house: the 20-minute walkthrough
Set a timer. Walk the house with this list:
- Replace the furnace filter — or at least check it. A filter you can't see light through is choking your system. Mark the date on the filter frame with a marker.
- Test every carbon monoxide detector — press the test button, then check the manufacture date on the back. Over 7 years old? Replace it. CO detectors expire silently.
- Test smoke detectors too — you're already on the ladder.
- Open all supply vents — closing vents in unused rooms doesn't save money on modern systems; it raises static pressure and overheats the heat exchanger. Every vent open, every return grille unblocked by furniture.
- Check the thermostat — set it to heat, bump it 5 degrees above room temp, and confirm the furnace fires and blows warm air within a few minutes. Dead display? Change the batteries first, then call if it's still dead.
- Sniff the first cycle — light dust-burn smell for a few hours is normal. Anything metallic, electrical, or sweet that persists past day one is a call-us smell.
- Walk the vents — feel airflow at every register. A dead register means a disconnected duct or a damper issue, both cheap to fix now.
Outside: the furnace's breathing room
Your furnace and its venting live half their life outdoors:
- Clear the outdoor vents — high-efficiency furnaces vent through sidewall pipes. Make sure they're not buried in leaves, blocked by stored items, or (later) snowdrift-prone. Blocked intake = shutdown.
- Trim back bushes from around the vent terminations — 2 feet of clearance.
- Check the condensate drain exit if your high-efficiency furnace drains outside — it can freeze and back up in a hard cold snap. Insulation on that line is cheap prevention.
- Note the flue — from the ground, look for obvious damage, bird nests, or disconnections on the exhaust. Don't climb up; just look.
What the tech handles (book it now, not later)
The homeowner checklist catches airflow and obvious problems. It does not catch cracked heat exchangers, weak ignitors, failing capacitors, or gas pressure drift — that's the 21-point tune-up, and October is when to book it. Here's why the timing matters practically: our schedule in October has same-week openings; the week after the first hard freeze, it's emergency-only triage.
When you call, say the words “I have a furnace… I would like to be checked for the winter.” We'll know exactly what you need — it's our most common October call, and there's a reason the checklist exists.
The $30 October supply run
Keep it simple. One trip:
- Furnace filters — buy two, so the mid-winter swap is already in the house (check your size first; it's printed on the filter frame).
- Thermostat batteries — AA or AAA lithium, even if the display looks fine.
- One spare CO detector if any of yours are past the 7-year mark.
Total: about thirty bucks. The most cost-effective HVAC spending in existence.
Renters and landlords: who does what
Landlords in Colorado are responsible for keeping heating equipment functional — but filters and detector batteries usually fall to the tenant in the lease. If you're renting in Aurora and the furnace hasn't been serviced, ask your landlord for the service record in writing. If you're the landlord with 1960s rentals in 80011, the October tune-up across your units is cheaper than one January emergency call per property.
What the tech's October visit covers that you can't DIY
The homeowner checklist handles airflow and obvious problems. Here's what only the tune-up catches — and why each matters before winter:
- Heat exchanger inspection — needs the burner assembly opened and often a camera scope. Cracks are invisible from outside the cabinet.
- Gas pressure and combustion analysis — requires a manometer and combustion analyzer. Drifted gas pressure wastes fuel and produces carbon monoxide; you can't eyeball it.
- Electrical testing — capacitor values, motor amp draws, control board function. Components test “weak” months before they test “dead,” and weak is when you want to know.
- Flame sensor and ignitor measurement — not just “does it light” but the microamp and resistance readings that predict this winter's reliability.
- Temperature rise verification — confirms airflow and firing rate are matched. Wrong rise shortens exchanger life silently.
Think of it as the difference between checking your car's tires (you) and putting it on the lift (the shop). Both matter; neither replaces the other.
Done the homeowner half? We'll do the tech half
21-point tune-up, written readings, scheduled before the freeze — not during it.
Frequently asked questions
When is the best time to do this checklist?
Early to mid-October — before the first hard freeze, while parts and appointments are plentiful. Late September is fine too; November is late.
My furnace ran fine all last winter. Do I still need the tune-up?
Yes. Last winter's performance tells you nothing about this winter's ignitor or heat exchanger. The parts that fail in January were weakening all last season.
Should I cover my outdoor AC unit for winter?
Not necessary in Aurora and can trap moisture. Clear debris around it and leave it uncovered — just make sure the furnace sidewall vents (different pipes) stay clear.
How do I know what size filter to buy?
It's printed on the cardboard frame of your current filter (e.g., 16x25x1). Take a photo of it at the store. When in doubt, bring the old filter with you.
I just moved to Aurora from a warm climate. What's different?
Everything freezes harder and faster than you expect, the furnace runs 5+ months straight, and the October prep window is real — skip it your first year and you'll learn why everyone does it. Welcome; call us before the first freeze.
What if I skipped last year's tune-up too?
Then this year's is doubly important — two seasons of wear with no inspection is when we find the cracked exchangers and dead capacitors. Mention the gap when you book; the tech will spend extra time on the safety checks.
The bottom line: October is the month Colorado gives you to prepare, and it's short. Do the 20-minute homeowner walkthrough this weekend, book the tune-up before the first hard freeze, and spend the $30 on filters and batteries. Every January emergency call we run is a version of this checklist that didn't happen — be the house that just stays warm.
PROUDLY SERVING AURORA, CO 80012