After 52 years of heating homes in Snohomish County, we've seen it all. The middle-of-the-night breakdowns. The "my furnace was fine yesterday" calls. The preventable repairs that ended up costing thousands.
Most furnace problems that happen during winter could have been prevented with a little fall maintenance. Here's how to make sure your system is ready.
Before You Start: Safety First
⚠️ Important Safety Note
If you smell gas, see visible damage to your furnace, or notice anything unusual, don't try to diagnose it yourself. Turn off the system and call a professional. Some furnace problems involve electrical hazards or gas leaks that require trained technicians.
DIY Maintenance You Can Do Today
1. Replace Your Filter
This is the single most important thing you can do for your furnace. A dirty filter is the #1 cause of furnace problems we see—and it's completely preventable.
When your filter is clogged:
- Your furnace works harder, driving up energy bills
- Reduced airflow can cause overheating and system shutdowns
- Your heat exchanger is under stress, which can lead to cracks
- Your home gets dusty and air quality suffers
💡 Filter Replacement Schedule
Standard 1" filters: Every 1-3 months during heating season. If you have pets or allergies, lean toward monthly. Thicker 4" filters can last 6-12 months, but check them quarterly.
2. Check Your Thermostat
Before the cold hits, make sure your thermostat is working properly:
- Switch it to "heat" mode and set it a few degrees above room temperature
- Listen for the furnace to kick on within a minute or two
- Feel the vents to confirm warm air is flowing
- If you have a programmable thermostat, update the schedule for fall/winter
If your thermostat uses batteries, replace them now. A dead battery in January is never fun.
3. Clear the Area Around Your Furnace
Your furnace needs breathing room. We often find furnaces surrounded by storage boxes, holiday decorations, or laundry. This is a fire hazard and can affect performance.
Keep at least 3 feet of clearance on all sides of your furnace. No flammable materials nearby. No clothes draped over it.
4. Check Your Vents and Registers
Walk through your home and check each vent:
- Make sure nothing is blocking them (furniture, rugs, curtains)
- Open any closed registers—closing too many can create pressure problems
- Vacuum out any dust or debris
5. Test Your Carbon Monoxide Detectors
Every home with a gas furnace should have CO detectors. Test them now and replace batteries. If you don't have CO detectors on every level of your home, install them before heating season begins.
Fall Furnace Checklist
- Replace furnace filter
- Test thermostat in heat mode
- Replace thermostat batteries
- Clear 3 feet around furnace
- Check all vents are unblocked
- Test CO detectors
- Check exterior vents for debris
- Listen for unusual noises during startup
- Schedule professional tune-up
When to Call a Professional
While the above tasks are safe for homeowners, some maintenance requires a professional. We recommend annual tune-ups that include:
- Heat exchanger inspection — Cracks can leak carbon monoxide
- Burner cleaning and adjustment — Ensures efficient combustion
- Electrical connection check — Loose connections cause failures
- Gas pressure testing — Improper pressure reduces efficiency
- Safety control testing — Verifies shut-off systems work
- Carbon monoxide testing — Checks for dangerous leaks
A professional tune-up typically costs $100-150 and takes about an hour. It's cheap insurance against mid-winter breakdowns and can extend your furnace's life by years.
Warning Signs to Watch For
During the first few days of running your furnace, pay attention to how it sounds and performs. Call a professional if you notice:
- Unusual noises — Banging, squealing, or rattling
- Yellow pilot light — Should be blue; yellow indicates incomplete combustion
- Short cycling — Furnace turns on and off frequently
- Cold spots — Uneven heating throughout the house
- Burning smell — A brief dusty smell at first startup is normal; anything else is not
- Higher bills — Sudden increase without usage change
How Old Is Your Furnace?
If your furnace is over 15 years old, this fall might be the time to start thinking about replacement—especially if you're facing repairs. Here's our general guidance:
- Under 10 years: Repair makes sense for most issues
- 10-15 years: Weigh repair costs against system age
- 15+ years: Major repairs often aren't worth it
New high-efficiency furnaces can reduce your heating costs by 20-30% compared to older models. If you're paying for repairs on an old, inefficient system, that money might be better invested in a new one.
The Bottom Line
A little preparation now prevents a lot of headaches later. The calls we get on the coldest day of the year are almost always preventable with basic maintenance.
Change your filter. Test your system. Schedule a tune-up. Your future self—shivering in a cold house, waiting for emergency service—will thank you.