As the fog rolls in and nights turn crisp, most of us in Marin County and San Francisco start relying on our heating systems again. But before winter really sets in, it’s smart to make sure your furnace is ready for the cooler months ahead.
Even a well-maintained furnace can show subtle signs of trouble before it stops working altogether- and catching them early can save you from a chilly night (and a costly emergency repair later).
Here are the top signs your furnace may need repair before winter hits, plus a few practical tips for keeping your system in top shape.
1. You Notice Strange Smells When the Heat Turns On
If you smell something unusual when your furnace starts up- like a burning, musty, or metallic odor- don’t ignore it.
- A dusty smell may be normal the first time you run your heat each season, as dust burns off internal components.
- A musty smell could mean moisture or mild mold inside your ductwork.
- A metallic or electrical smell can indicate overheating or wiring issues- something that needs professional attention right away.
Pro tip: If the smell lingers for more than an hour, shut off your furnace and call for an inspection.
2. Your Furnace Makes Odd Noises
All furnaces make some noise, but banging, rattling, whistling, or grinding are not normal.
Common causes include:
- Loose or unbalanced blower components
- Worn-out bearings or belts
- Airflow blockages in ducts or vents
- Delayed ignition (which can cause a small “boom” sound)
If your furnace sounds different than it used to, it’s best to have it checked before those noises turn into breakdowns.
3. Uneven Heat or Cold Spots Around Your Home
If one room feels warm while another stays cold, your system may be struggling with:
- Airflow restrictions in the ductwork
- A malfunctioning blower motor
- Thermostat calibration issues
- Leaks in ducts (especially common in older Marin homes)
Over time, uneven heat can also signal a furnace that’s losing efficiency- meaning higher energy bills for less comfort.
4. Short Cycling- Furnace Turning On and Off Frequently
If your furnace keeps cycling on and off every few minutes, that’s called short cycling. It’s one of the most common early signs of trouble.
Short cycling can happen due to:
- A dirty air filter
- Blocked vents or intake
- Overheating sensors or a failing thermostat
This not only wears down your system but also spikes energy use. A quick tune-up often fixes it and helps your system run longer with fewer repairs.
5. Weak or No Airflow from Vents
Weak airflow can indicate a clogged filter, failing blower motor, or duct leak. It can also point to issues with your furnace’s fan control board.
If your vents are barely pushing out warm air- or some vents aren’t blowing at all- don’t wait until temperatures drop further. A small airflow issue today can become a full heating failure later.
6. Your Energy Bills Are Climbing
If your energy bills are creeping up without a clear reason, it’s often a sign your furnace is working harder than it should. Efficiency loss can happen gradually due to dirty components, worn parts, or poor airflow.
Scheduling a professional tune-up before winter can restore efficiency and catch small problems before they become expensive ones.
7. The Furnace Struggles to Stay On
If your furnace starts but won’t stay running – or takes a few tries to ignite- that’s a red flag. Common culprits include a failing ignition system, thermocouple issues, or clogged burners. These are all fixable with the right technician but shouldn’t be ignored.
What to Do If You Notice These Signs
Don’t panic- most furnace issues are minor when caught early. A pre-winter inspection can identify and fix small problems before they affect performance.
At Bay Air Heating & Cooling, we check:
- Burners, heat exchangers, and ignition components
- Thermostat calibration
- Airflow and duct efficiency
- Safety controls and carbon monoxide output
Our goal is to keep your system reliable, efficient, and safe all season long.
Why It Matters in Marin County
Homes in Marin and San Francisco often deal with coastal humidity and salt air, which can wear down components faster. Regular maintenance isn’t just about comfort- it’s about protecting your furnace from early corrosion and performance loss.
Even a quick annual tune-up can extend your furnace’s lifespan by several years and reduce your energy costs through the winter.