October is the sweet spot for HVAC prep in Minnesota — the AC season is over, first frost is coming, and HVAC companies aren't yet slammed with emergency calls. Here's a comprehensive checklist to make sure your heating system is ready before the temperature drops below freezing and stays there.
DIY Tasks (Do These Yourself)
1. Replace the Air Filter
Start the heating season with a fresh filter — MERV 8 to MERV 11 for most homes, or replace the annual media filter in your 4-inch cabinet. A clean filter ensures maximum airflow efficiency from day one.
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2. Test the Thermostat
Switch from COOL to HEAT. Set the temperature above the current room temp and confirm the furnace fires. If you have a smart thermostat, verify the schedule is set for heating season. Replace batteries in the thermostat if it's been more than a year.
3. Check All Supply and Return Registers
Walk through the house and confirm all registers are open and unobstructed. Furniture moved during summer can inadvertently block returns. Check that no rooms have closed registers — this creates back-pressure that strains the blower and can cause overheating.
4. Clear the Area Around the Furnace
Remove any storage that accumulated near the furnace over summer. The area around the furnace should have at least 3 feet of clearance. Check that nothing is blocking the air intake or exhaust pipes (for 96% AFUE units — the PVC pipes exiting through the exterior wall).
5. Test Carbon Monoxide Detectors
Press the test button on every CO detector. Replace batteries. CO detectors have a lifespan of 5–7 years — check the manufacturing date on the back. If it's expired, replace it before heating season. Minnesota law requires CO detectors in all homes with fossil-fuel heating.
6. Inspect the Condensate Drain Line (High-Efficiency Furnaces)
Check that the condensate drain is clear. Pour a cup of water into the condensate trap and watch it drain. A clogged drain causes a pressure switch fault and will shut the furnace down — better to discover this in October than January.
7. Check the Exterior PVC Pipes (96% AFUE Units)
Go outside and look at the furnace exhaust and intake pipes. Confirm nothing is nesting in them (birds and mice love these in summer), no debris has collected, and they're still properly secured to the exterior wall. Install mesh screens if you don't have them.
8. Check the Furnace Flame (After Startup)
After the furnace fires for the first time, look through the sight window at the flame color. Should be blue with a small yellow tip. Mostly yellow or orange flame indicates incomplete combustion — call a tech.
Professional Service Tasks (Schedule a Tech)
| Task | Why It Matters | Typical Cost |
|---|---|---|
| Annual furnace tune-up | Checks heat exchanger, burners, flue, safety switches, gas pressure, and efficiency | $80–$150 |
| Heat exchanger inspection | Detects cracks that could allow CO to enter living space | Included in tune-up |
| Combustion analysis | Measures CO in flue and efficiency of combustion | Included in tune-up |
| Blower motor cleaning/lubrication | Reduces noise, extends motor life, improves airflow | Included in tune-up |
| Gas pressure check | Verifies manifold pressure matches burner spec | Included in tune-up |
| Flue pipe inspection | Checks for corrosion, gaps, or blockage | Included in tune-up |
AC Winterization
- Clean the outdoor condenser: Rinse debris from the fins with a garden hose (turn off power first)
- Cover the unit (optional): A cover prevents debris accumulation but can trap moisture — use a breathable cover or skip it entirely; modern AC condensers are designed to handle Minnesota winters uncovered
- Turn off the AC disconnect: The outdoor electrical disconnect box — flip it off for winter to prevent the compressor from attempting to run on a warm January day
When to Skip the Checklist and Just Replace
If your furnace is 15+ years old, is showing error codes regularly, has needed 2+ repairs in the past 3 years, or your heating bills have climbed year-over-year with no obvious cause — an October replacement is the smart call. You'll pay winter rates plus installation labor. If the furnace dies in January, you're looking at emergency rates, possible waiting periods, and the risk of frozen pipes.
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Tell us a little about your home and what you're replacing. We'll send real numbers on a Goodman 96% AFUE setup — shipped direct to your door anywhere in the lower 48. No contractor markup, no obligation.